Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
METHODS OF DYEING A SUBSTRATE USING A MODIFIED INDIGO COMPOUND
Document Type and Number:
WIPO Patent Application WO/2019/126488
Kind Code:
A1
Abstract:
The present disclosure provides dye compounds for use in dyeing textiles.

Inventors:
PUVVADA SUDHAKAR (US)
SCHEER DENNIS (US)
HOERTZ PAUL GERARD (US)
Application Number:
PCT/US2018/066778
Publication Date:
June 27, 2019
Filing Date:
December 20, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
VF JEANSWEAR LP (US)
PUVVADA SUDHAKAR (US)
SCHEER DENNIS (US)
HOERTZ PAUL GERARD (US)
International Classes:
D06P1/22; D06P1/00; D06P1/96
Domestic Patent References:
WO2017223369A12017-12-28
Foreign References:
GB186057A1924-02-07
US1448251A1923-03-13
Other References:
S. N. CHATTOPADHYAY ET AL: "Dyeing of Jute Fabric Using Indigosol Dyes", JOURNAL OF NATURAL FIBERS, vol. 6, no. 1, 6 March 2009 (2009-03-06), US, pages 98 - 107, XP055574575, ISSN: 1544-0478, DOI: 10.1080/15440470802703596
"Hauser, Improved Determination of Indigo", TEXTILE CHEMIST AND COLORIS & AMERICAN DYESTUFF REPORTER, vol. 32, no. 2, December 2000 (2000-12-01), pages 33
"Denim, Manufacture, Finishing and Applications", 23 April 2015, WOODHEAD PUBLISHING
"Handbook of Textile and Industrial Dyeing, Principles, Processes and Types of Dyes", 25 October 2011, WOODHEAD PUBLISHING
"Handbook of Textile and Industrial Dyeing, Volume 2: Applications of Dyes", vol. 2, 25 October 2011, WOODHEAD PUBLISHING
Attorney, Agent or Firm:
RIESEN, Michael J. (US)
Download PDF:
Claims:
What is Claimed Is:

1. A method for dyeing a substrate, comprising:

(i) pretreating the substrate;

(ii) dyeing the substrate with a dye compound comprising an indigo derivative, or a salt thereof, having one or more modification over the chemical structure of indigo, wherein the indigo derivative has a water-solubility of greater than 0.2% w/v in the absence of a reducing agent and in the presence oxygen, and converts to indigo upon removing the modification, wherein the chemical structure of indigo is the following:

(iii) hydrolyzing the substrate at a temperature of about 20 to about 80°C.

2. The method of claim 1, wherein the one or more modification enhances the aqueous solubility of the dye compound lacking the modification.

3. The method of claim 1 or 2, wherein the one or more modification is a substituent on indigo or the indigo derivative.

4. The method of claim 2 or 3, wherein the substituent is on one or both nitrogen atoms.

5. The method of claim 2 or 3, wherein the substituent is on one or more carbon atom.

6. The method of claim 2 or 3, wherein the substituent is on one more both oxygen atoms.

7. The method of any one of claims 3-6, wherein the substituent is an alkyl, cycloalkyl, alkoxy, halide, acyl, amine, ester, amide, aryl, heteroaryl, heterocyclyl, sulfonate, carbamate, urea, imine, oxime, anhydride, CN, NCh, mesylate, or tosylate, wherein each is optionally substituted.

8. The method of any one of claims 1-7, wherein the reducing agent is sodium hydrosulfite, formamidine sulfmic acid, glucose, sodium borohydride, sodium metabisulfite, thiourea dioxide, cellobiose, glyceraldehyde, or fructose.

9. The method of any one of the preceding claims, wherein the compound is of Formula (I) or (II):

wherein:

R1 and R2 are, independently, H, SCbR0, SC R0, PCb(Rc)2, C(0)NRARB, C(O)-

(optionally substituted Ci-6alkyl), C(0)-(optionally substituted aryl), C(0)-(optionally substituted Ci-9glycolyl), C(0)-(optionally substituted heteroaryl), C(0)-(optionally substituted heterocyclyl), C(0)-(optionally substituted Ci-6hydroxyalkyl), C(0)0- (optionally substituted Ci-6alkyl), C(0)0-(optionally substituted aryl), C(0)0- (optionally substituted Ci-9glycolyl), C(0)0-(optionally substituted Ci- 6hydroxyalkyl), C(0)0-(optionally substituted heteroaryl), C(0)0-(optionally substituted heterocyclyl); or

R3 and R4 are, independently, H, halide, optionally substituted Ci-6alkyl, optionally substituted Ci-6hydroxyalkyl, optionally substituted Ci-6alkoxy, optionally substituted aryl, or SO3H;

R7 and R8 are, independently, H, SCbR0, SC R0, PCb(Rc)2, C(0)NRARB, C(O)-

(optionally substituted Ci-6alkyl), C(0)-(optionally substituted aryl), C(0)-(optionally substituted Ci-9glycolyl), C(0)-(optionally substituted Ci-6hydroxyalkyl), C(O)- (optionally substituted heteroaryl), C(0)-(optionally substituted heterocyclyl), C(0)0-(optionally substituted Ci-6alkyl), C(0)0-(optionally substituted aryl), C(0)0-(optionally substituted Ci-9glycolyl), C(0)0-(optionally substituted Ci- 6hydroxyalkyl), C(0)0-(optionally substituted heteroaryl), or C(0)0-(optionally substituted heterocyclyl);

RA and RB are, independently, H or optionally substituted Ci-6alkyl, or optionally substituted aryl;

Rc is H, optionally substituted Ci-6alkyl, optionally substituted C3-scycloalkyl,

optionally substituted aryl, optionally substituted heteroaryl, or optionally substituted heterocyclyl;

m and n are, independently, 0 to 4;

or a salt thereof.

10. The method of claim 9, wherein when the compound is of Formula (I), R3 and R4 are not H, when R1 and R2 are both l-methyl-pyridyl-3-yl.

11. The method of claim 9 or 10, wherein m is 0.

12. The method of any one of claims 9-11, wherein n is 0.

13. The method of claim 9 or 10, wherein R3 is a halide.

14. The method of any one of claims 9, 10, or 13, wherein R4 is a halide.

15. The method of any one of claims 9, 10, or 14, wherein R3 is Ci-6alkyl.

16. The method of any one of claims 9, 10, 13, or 15, wherein R4 is Ci-6alkyl.

17. The method of any one of claims 9-16, wherein one of R1 or R2 is H.

18. The method of any one of claims 9-17, wherein one of R1 and R2 is SO3H.

19. The method of any one of claims 9-18, wherein the compound is of Formula (I):

20. The method of any one of claims 9-19, wherein one or both of R1 and R2 is C(O)- (optionally substituted heteroaryl).

21. The method of any one of claims 9-20, wherein one or both of R1 and R2 is C(O)- (optionally substituted pyridyl), such as C(0)-(optionally substituted 2-pyridyl), C(O)- (optionally substituted 3-pyridyl), or C(0)-(optionally substituted 4-pyridyl).

22. The method of claim 21, wherein the pyridyl is substituted with Ci-6alkyl.

23. The method of claim 21 or 22, wherein the pyridyl is substituted with one or more methyl or ethyl.

24. The method of any one of claims 21-23, wherein the pyridyl is substituted on the N-atom.

25. The method of any one of claims 9-19, wherein one or both of R1 and R2 is C(O)- (optionally substituted aryl), such as C(0)-(optionally substituted phenyl).

26. The method of any one of claims 9-19, wherein one or both of R1 and R2 is C(0)NRARB, wherein one or both of RA and RB is H, optionally substituted Ci-6hydroxyalkyl, or optionally substituted Ci-6alkyl.

27. The method of any one of claims 9-19, wherein one or both of R1 and R2 are C(0)0- (optionally substituted heterocyclyl) such as C(0)0-(optionally substituted pyrrolidone).

28. The method of any one of claims 9-19, wherein one or both of R1 and R2 are, independently, C(0)0-(optionally substituted alkyl) such as C(0)0(alkyl substituted with heterocyclyl) such as C(0)0(alkyl substituted with glucosyl).

29. The method of any one of claims 9-19, wherein one or both of R1 and R2 are, independently, C(0)(optionally substituted Ci-6hydroxyalkyl).

30. The method of any one of claims 9-19, wherein one or both of R1 and R2 are, independently, C(0)0(optionally substituted Ci-6hydroxy alkyl).

31. The method of any one of claims 9-19, wherein one or both of R1 and R2 are, independently, C(0)(optionally substituted Ci-9glycol).

32. The method of any one of claims 9-18, wherein the compound is of Formula (II):

33. The method of claim 32, wherein one or both of R1 and R2 are H.

34. The method of claim 32 or 33, wherein one or both of R7 and R8 are H.

35. The method of claim 32 or 33, wherein one of R7 and R8 are SO3H.

36. The method of claim 32 or 33, wherein one or both of R7 and R8 are C(0)(optionally substituted heteroaryl) such as C(0)(optionally substituted pyridyl).

37. The method of claim 32 or 33, wherein one or both of R7 and R8 are C(0)(optionally substituted Ci-6alkyl).

38. The method of claim 37, wherein the Ci-6alkyl is substituted with C(0)0(Ci-6alkyl) such as C(0)0CH2CH3.

39. The method of claim 32 or 33, wherein one or both of R7 and R8 are C(0)-(optionally substituted aryl) such as C(0)-(optionally substituted phenyl).

40. The method of claim 39, wherein the phenyl is substituted with CC H.

41. The method of any one of the preceding claims which is an acid or base addition salt.

42. The method of any one of the preceding claims, which is a sulfate salt, alkylsulfate salt, bisulfate salt, phosphate salt, or halide salt.

43. The method of claim 42, wherein the halide salt is an iodide salt, chloride salt, bromide salt, or fluoride salt.

44. The method of claim 42, wherein the compound is an alkylsulfate salt.

45. The method of claim 44, wherein the compound is a methylsulfate or ethylsulfate salt.

46. The method of claim 9 or 10, wherein the compound is of Formula (IA):

wherein:

R5 and R6 are, independently, H or Ci-6alkyl; and

X is halide, sulfate, Ci-6alkylsulfate, bisulfate, or phosphate;

with the proviso that both R5 and R6 are not CFb when X is CFbSCri .

47. The method of claim 9, wherein the compound is of Formula (IB) or (IC):

wherein:

R5 and R6 are, independently, H or Ci-6alkyl; and

X is halide, sulfate, Ci-6alkylsulfate, bisulfate, or phosphate.

48. The method of claim 9, wherein the compound is:

wherein X is a counteranion.

49. The method of claim 9, wherein the compound is:

wherein X is acetate, propionate, lactate, citrate, tartrate, succinate, fumarate, maleate, malonate, mandelate, phthalate, Cl, Br, I, F, phosphate, nitrate, sulfate, ethanes ulfonate, phosphonate, naphthalenesulfonate, benzenesulfonate, toluenesulfonate, camphorsulfonate, methanes ulfate, ethanes ulfonate, naphthalenes ulfate, benzenesulfate, toluenesulfate, camphorsulfate, bisulfate, sulfite, or bisulfite.

50. The method of claim 9, wherein the compound is:

wherein, X is a counteranion.

51. The method of claim 9, wherein the compound is:

52. The method of claim 9, wherein the compound is:

53. The method of claim 9, wherein the compound is: or salt thereof.

54. The method of claim 9, wherein the compound is: or a salt thereof.

55. The method of claim 9, wherein the compound is:

, or a salt thereof.

56. The method of claim 9, wherein the compound is: or a salt thereof.

57. The method of claim 9, wherein the compound is:

or a salt thereof.

58. The method of any one of the preceding claims, wherein the compound converts to indigo through hydrolysis.

59. The method of any one of the preceding claims, wherein the compound is substantially stable in the presence of oxygen such as in aqueous solutions.

60. The method of any one of the preceding claims, wherein the compound has greater water solubility than indigo.

61. The method of any one of the preceding claims, wherein the compound is mixed with water.

62. The method of claim 61, wherein the water is acidic.

63. The method of claim 61 or 62, wherein the water further comprises one or more additional components.

64. The method of claim 63, wherein said additional component is an acid, cationic agent, caustic agent, chelating agent, color retention agent, coloring agent, dispersant, foaming agent, hydrolyzing agent, mercerization reagent, penetration enhancer, pH buffering agent, salt, solubilizing agent, stabilizing agent, surfactant, thickening agent, tracer, viscosity modifier, or wetting agent.

65. The method of any one of the preceding claims, wherein the pretreating is performed using an anti-migrant, pH buffering agent, anionic agent, hydrolysis catalyst of alkali agent.

66. The method of any one of the preceding claims, wherein the pretreating is performed using a carboxylate salt, phosphate salt, sodium salt of polyacrylic acid, derivative of polyacrylate, copolymer of polyacrylate, polymaleic acid, sodium bicarbonate, sodium carbonate, sodium citrate, sodium citrate dibasic, tartrate salts, succinate salts, malonate salts, polymers comprising phosphate groups, or polymers comprising polyphosphate groups.

67. The method of claim 66, wherein the carboxylate salt is sodium acetate, sodium stearate, or a salt of lactic acid.

68. The method of claim 66, wherein the phosphate salt is sodium phosphate dibasic, sodium phosphate monobasic, or sodium pyrophosphate.

69. The method of any one of the preceding claims, wherein the temperature is about 40 to about 80°C.

70. The method of any one of the preceding claims, wherein the hydrolyzing is performed over about 5 seconds to about 5 minutes.

71. The method of any one of the preceding claims, further comprising:

(iii) rinsing the substrate from step (ii).

72. The method of claim 71, wherein rinsing is performed with an aqueous solution.

73. The method of claim 72, wherein the aqueous solution further comprises an organic solvent, acid, cationic agent, caustic agent, chelating agent, color retention agent, coloring agent, dispersant, foaming agent, hydrolyzing agent, mercerization reagent, penetration enhancer, pH buffering agent, salt, solubilizing agent, surfactant, thickening agent, tracer, viscosity modifier, or wetting agent.

74. The method of claim 72 or 73, wherein the aqueous solution further comprises a neutralization agent or buffering agent.

75. The method of claim 72, wherein the pH of the dyed substrate is adjusted to about 5 to about 9.

76. The method of any one of the preceding claims, wherein the substrate is a textile.

77. The method of any one of the preceding claims, wherein the substrate is a natural substrate such as a plant fiber such as cotton, kapok, hemp, bamboo, flax, sisal, jute, kenaf, ramie, bamboo, soybean, or coconut or an animal substrate such as silk, wool, leather, hair, or feather.

78. The method of any one of claims 1-76, wherein the substrate is a synthetic substrate such as a polyamide such as nylon, polyester, acrylic, polyolefin, or spandex.

79. The method of any one of the preceding claims, wherein the substrate is a yam.

80. The method of any one of claims 1-78, wherein the substrate is a package of yam.

81. The method of any one of claims 1-78, wherein the substrate is a fabric.

82. The method of any one of the preceding claims, wherein the dyeing comprises dip dyeing, rope dyeing, slasher dyeing, spray dyeing, continuous dyeing, piece dyeing, space dyeing, package dyeing, skein dyeing, garment dyeing, paint bmsh dyeing, airbrush dyeing, blotch dyeing, foam dyeing, stamping, embossing, brushing, kiss rolling, screen printing, digital printing, doctor blading, knife rolling, kiss rolling, or coating.

83. The method of any one of the preceding claims, wherein the dyeing is performed in the absence of a reducing agent to convert the compound to a leuco form of the compound.

84. The method of claim 83, wherein the reducing agent is sodium hydrosulfite, formamidine sulfmic acid, glucose, sodium borohydride, sodium metabisulfite, thiourea dioxide, cellobiose, glyceraldehyde, fructose, or combinations thereof.

85. A dyed substrate prepared according to any one of the preceding claims.

Description:
METHODS OF DYEING A SUBSTRATE USING A MODIFIED INDIGO COMPOUND

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No.

62/609,160, filed December 21, 2017, which is incorporated herein by reference.

TECHNICAL FIELD

[0002] This invention relates to methods for dyeing a dye substrate using a modified indigo compound.

BACKGROUND

[0003] Fabrics dyed with indigo, and especially denim fabrics, are desired by consumers due to the broad range of shades that can be achieved and the ability of the fabric to develop character by evolving over time. In traditional methods, indigo dyeing of cotton yam for denim fabrics is a difficult process, due largely to the challenges of dyeing with the indigo compound.

[0004] In conventional indigo dyeing, cotton yams are sequentially dipped into baths of leuco- indigo, a soluble and reduced form of indigo. High alkali concentration, pH 11+, and strong reducing agents are used to reduce indigo to the leuco state making it relatively water soluble. Additional alkali and reducing agent are added to the dyebath to prevent oxidation of leuco- indigo back to indigo. Indigo is not only hard to reduce, but also hard to keep in reduction and soluble. Leuco-indigo is very sensitive to air and will revert to insoluble indigo very quickly when exposed.

[0005] What is needed in the art are methods of indigo dyeing of substrates using less rigorous conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 are images of 3x1 twill cotton fabric dyed with Compound 8 exposed to l00°C for 4 minutes, exposed to l50°C for 4 minutes, and exposed to l80°C for 4 minutes.

[0007] FIG. 2 are images of cotton skeins pretreated with 1 M NaOH (aq), dyed with Compound 8 using a 3 wt.% solution, hydrolyzed using 1 M NaOH (aq), rinsed with water, and dried. In the case of the skein at the bottom, atmospheric steam was used to carry out the conversion to indigo. [0008] FIG. 3 are images 3x1 twill fabrics that were prepared for dyeing, padded using a 6% aqueous solution of Compound 8, and dried at 60°C. The top row are the samples as they appeared following drying. The samples the bottom row were subjected to 10 minutes in a controlled temperature and humidity chamber. The two samples on the left were not pretreated prior to padding. The middle two samples were padded and dried prior to padding with dye. The two samples on the right were padded and dried at 80°C prior to padding with dye.

[0009] FIG. 4 are images of digital printed fabrics using a 6% Compound 8 solvent-based ink., where a portion of the same sample was also treated following the drying step with a 1 M NaOH aqueous solution.

[0010] The present application is further understood when read in conjunction with the appended drawings. For the purpose of illustrating the subject matter, these are shown in the drawings exemplary embodiments of the subject matter; however, the presently disclosed subject matter is not limited to the specific compositions, methods, devices, and systems disclosed. In addition, the drawings are not necessarily drawn to scale.

SUMMARY

[0011] The disclosure provides methods for dyeing substrates, comprising (i) pretreating the substrate; (ii) dyeing the substrate with a dye compound comprising an indigo derivative, or a salt thereof, having one or more modification over the chemical structure of indigo, wherein the indigo derivative has a water-solubility of greater than 0.2% w/v in the absence of a reducing agent and in the presence oxygen, and converts to indigo upon removing the modification; and (iii) hydrolyzing the substrate at a temperature of about 20 to about 80°C. In some embodiments, the temperature is about 40 to about 80°C. In further embodiments, the hydrolyzing is performed over about 5 seconds to about 5 minutes.

[0012] The disclosure also provides dyed substrates prepared according to any of the methods disclosed herein.

[0013] Other aspects and embodiments of the invention will be readily apparent from the following detailed description of the invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0014] Embodiments of the present disclosure are directed to improved processes for indigo dyeing a substrate, such as cotton yam, using a modified indigo compound in place of leuco- indigo. The major benefit provided by this process includes a hydrolysis step that may be performed at much lower temperatures. The inventors found that pretreating the substrate permitted the use of lower temperatures during the hydrolysis. In doing so, the methods provide safer and more efficient hydrolyses, resulting in more efficient methods of dyeing a substrate.

[0015] The modification of the indigo compounds known in the art is environmentally friendly and atom efficient. It also is quickly and completely removable when exposed to a simple reagent or condition in order to leave standard indigo on the yam.

[0016] Accordingly, the dyeing process of embodiments of the present disclosure may be performed without the need for reducing agents in the dye bath. As such, the amount of reducing agents in the dye solution may be significantly decreased or, more preferably, the reducing agents may be eliminated from the dye solution altogether.

[0017] The oxygen stability of the modified indigo compound also renders it highly advantageous for foam dyeing processes, in which the dye comes into substantial contact with the atmosphere in which the process is performed. In part because of the instability of leuco- indigo in air, the foam dyeing of textile yams with indigo has yet to be commercially developed. This is, at least in part, due to the large amounts of an inert gas that are required in order to apply a foam containing leuco-indigo to a yam. In contrast, the modified indigo compounds may be applied to textile yams through a foam dyeing process that takes place in air, i.e. without the need for an inert gas environment.

[0018] Because the modified indigo compounds of the present disclosure tend to convert to indigo through hydrolysis, contact with water may cause the modified indigo compounds of the present disclosure to begin to convert into water-insoluble indigo. Since the dyeing process preferably comprises contacting the yam with an aqueous solution containing the modified indigo compound, stability of the modified indigo compound in aqueous solution is important commercially (e.g. for maintenance of a dye bath). Notably, the modified indigo compounds of the present disclosure are capable of remaining in aqueous solution for a commercially significant amount of time before substantial conversion to indigo occurs.

[0019] In some embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution (at room temperature) for a period of at least five minutes before substantial conversion to water-insoluble indigo occurs. In other embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least ten minutes before substantial conversion to water-insoluble indigo occurs. In further embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least thirty minutes before substantial conversion to the water-insoluble indigo compound occurs. In yet other embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least one hour before substantial conversion to water-insoluble indigo occurs. In still further embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least three hours before substantial conversion to water-insoluble indigo occurs. In other embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least ten hours before substantial conversion to water-insoluble indigo occurs. In further embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least fifteen hours before substantial conversion to water-insoluble indigo occurs. In yet other embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least twenty hours before substantial conversion to water-insoluble indigo occurs. In still further embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least one day before substantial conversion to water-insoluble indigo occurs. In other embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least one and one-half days before substantial conversion to water-insoluble indigo occurs. In further embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least two days before substantial conversion to water-insoluble indigo occurs. In still other embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least three days before substantial conversion to water-insoluble indigo occurs. In yet further embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least five days before substantial conversion to water-insoluble indigo occurs. In other embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least one week before substantial conversion to water-insoluble indigo occurs. In further embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least ten days before substantial conversion to water-insoluble indigo occurs. In still further embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least two weeks before substantial conversion to water-insoluble indigo occurs. In yet other embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least three weeks before substantial conversion to water-insoluble indigo occurs. In further embodiments, the modified indigo compounds of the present disclosure remain in aqueous solution for a period of at least one month (i.e. 30 days) before substantial conversion to water-insoluble indigo occurs.

[0020] The modified indigo compound may also have improved water solubility relative to conventional leuco-indigo.

[0021] The modified indigo compounds of the present disclosure also have increased water solubility when compared to leuco-indigo. Accordingly, dyeing yams with the modified indigo compound provides a process in which more indigo dye can be placed on the yam per period of contact relative to conventional dyeing methods. In this way, by using a modified indigo compound of the present disclosure, one may increase the speed, and thus the output, of the process by reducing the amount of time that the yam spends in a dye bath per dip and/or the number of dips to which the yam is subjected. Moreover, one may obtain a darker indigo dye using a relatively lower contact time and/or fewer dips than would be necessary using a conventional leuco-indigo dye bath. In some embodiments, for example, the concentration of the modified indigo compound in an aqueous dye solution may be at least 0.3 wt.%, at least 0.5 wt.%, at least 0.6 wt.%, at least 0.8 wt.%, at least 1 wt.%, at least 2 wt.%, at least 3 wt.%, at least 5 wt.%, at least 10 wt.%, at least 15 wt.%, or at least 20 wt.%.

[0022] The improved water solubility of the modified indigo compounds of the present disclosure also simplifies the process by which the dye bath is controlled, and, more particularly, by which the modified indigo compound is maintained at a substantially constant concentration within the dye bath. This, in turn, minimizes the inclusion of additional chemicals, which leads to decreased costs and a lower environmental impact.

[0023] As described above, the modified indigo compounds disclosed herein have a beneficial combination of (a) greater oxygen stability than leuco-indigo (such as may be measured at room temperature) and (b) greater water solubility than leuco-indigo (such as may be measured at room temperature). In some embodiments, the modified indigo compounds may further have (c) greater affinity to cotton than leuco-indigo.

[0024] In the present disclosure the singular forms "a", "an" and "the" include the plural reference, and reference to a particular numerical value includes at least that particular value, unless the context clearly indicates otherwise. Thus, for example, a reference to "a material" is a reference to at least one of such materials and equivalents thereof known to those skilled in the art, and so forth.

[0025] When a value is expressed as an approximation by use of the descriptor "about" or "substantially" it will be understood that the particular value forms another embodiment. In general, use of the term "about" or "substantially" indicates approximations that can vary depending on the desired properties sought to be obtained by the disclosed subject matter and is to be interpreted in the specific context in which it is used, based on its function. The person skilled in the art will be able to interpret this as a matter of routine. In some cases, the number of significant figures used for a particular value may be one non-limiting method of determining the extent of the word "about" or "substantially". In other cases, the gradations used in a series of values may be used to determine the intended range available to the term "about" or "substantially" for each value. Where present, all ranges are inclusive and combinable. That is, references to values stated in ranges include every value within that range.

[0026] When a list is presented, unless stated otherwise, it is to be understood that each individual element of that list and every combination of that list is to be interpreted as a separate embodiment. For example, a list of embodiments presented as "A, B, or C" is to be interpreted as including the embodiments, "A," "B," "C," "A or B," "A or C," "B or C," or "A, B, or C."

[0027] It is to be appreciated that certain features of the invention which are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. That is, unless obviously incompatible or excluded, each individual embodiment is deemed to be combinable with any other embodiment(s) and such a combination is considered to be another embodiment. Conversely, various features of the invention that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any sub-combination. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as "solely," "only" and the like in connection with the recitation of claim elements, or use of a "negative" limitation. Finally, while an embodiment may be described as part of a series of steps or part of a more general structure, each said step may also be considered an independent embodiment in itself. I. The Compounds

[0028] In solving the problems in the art, the inventors developed modified dye molecules that are likely to bond more strongly to cotton than in the current dyeing process, are soluble in water, can be converted to indigo in one simple step after dyeing, are cost effective or provide a cost saving over the current process, more stable than leuco-indigo, and/or readily dissolves in water, unlike standard, indigo, and readily converts back to indigo quickly and easily without skying.

[0029] Furthermore, core dyeing of yam with the modified dye molecule is possible and controllable; there is a large reduction in production water and waste water; there is a reduction in the chemicals required for the process; the molecule, auxiliary chemistries, and effluent are likely to be suitable for standard wastewater treatment processes; the modification is introduced to indigo in a few simple steps, and is stable; the molecule could be supplied to dye houses in its modified form; and no reducing agents are required. Such benefits can be gleaned using all forms of dyeing, including those discussed below.

[0030] The present disclosure provides dye compounds for use in dyeing substrates. The dye compounds comprise an indigo derivative, or a salt thereof, having one or more modification over the chemical structure of indigo. The inventors found that these compounds convert to indigo via hydrolysis. In some embodiments, hydrolysis is accomplished using a hydrolyzing agent, heat, steam, or combinations thereof. Advantageously, these compounds were found to be substantially stable in the presence of an oxidant such as in aqueous solutions, which property is not shared with leuco-indigo. Preferably, the compounds were found to be substantially stable in the presence of oxygen. These compounds were also found to be more stable in the air than other indigo derivatives such as leuco-indigo.

[0031] The term "substantially stable" refers to the ability of the compound to maintain its structure and properties thereof. In some embodiments, a compound's stability is maintained without being reduced, oxidized, or reacting with another component of the composition or method discussed herein. In other embodiments, the compound is stable since it maintains its water solubility. In further embodiments, the compound is stable since it does not convert to indigo. Desirably, less than about 50 wt.%, such as less than about 45, less than about 40, less than about 35, less than about 30, less than about 25, less than about 20, less than about 15, less than about 10, or less than about 5 wt.% of the compound in an aqueous solution degrades under atmospheric conditions over a period of about 12 hours in the absence of a reducing agent. Degradation can be measured using any analytical technique which is capable of quantifying a chemical compound including, without limitation, gas chromatography, UV -visible spectrophotometry, nuclear magnetic resonance, mass spectroscopy, or combinations thereof. In some embodiments, about 0.001 to about 50 wt.% of the compound, about 0.001 to about 45, about 0.001 to about 40, about 0.001 to about 35, about 0.001 to about 30, about 0.001 to about 25, about 0.001 to about 20, about 0.001 to about 15, about 0.001 to about 10, or about 0.001 to about 5 wt.% of the compound in an aqueous solution degrades under atmospheric conditions over a period of about 12 hours in the absence of a reducing agent. In further embodiments, 0.001 to about 5 wt.% of the compound in an aqueous solution degrades under atmospheric conditions over a period of about 12 hours in the absence of a reducing agent.

[0032] The inventors also found that the compounds described herein have greater water solubility than indigo. In some embodiments, the dye compounds have a water solubility of about 0.2% w/v or greater. In preferred embodiments, the water solubility is about 0.2% w/v or greater in the absence of a reducing agent. In other preferred embodiments, the water solubility is about 0.2% w/v or greater in the presence of oxygen. In yet further embodiments, the water solubility is about 10 to about 100%, about 20 to about 100, about 30 to about 100, about 40 to about 100, about 50 to about 100, about 60 to about 100, about 70 to about 100, about 80 to about 100, about 90 to about 100, about 95 to about 100, about 98 to about 100, about 99 to about 100, or about 100 w//v. The water solubility of the compounds described herein may be measured using techniques known to those skilled in the art including, without limitation, dissolution with agitation, followed by filtration of centrifugation to isolate the soluble solids. The insoluble solids are then dried and weighed and the solubility calculated.

[0033] The term "indigo" as used herein refers to the following compound.

[0034] Similarly, the term "leuco-indigo" is used interchangeably with "indigo white" and refers to the following compound. In some embodiments, leuco-indigo exists in the neutral form.

[0035] Leuco-indigo may also exist in a deprotonated form, such as a form which is deprotonated on one or both oxygen atoms. Thus, the term "leuco-indigo" can include the mono anionic and di-anionic forms including the monosodium, monopotassium, monolithium, disodium, dipotassium, or dilithium analogs of the following:

[0036] Thus, the one or more modification is designed to enhance the aqueous solubility of the dye derivative lacking the modification. The term, "enhance" as used herein refers to improving the solubility to the dye derivative lacking the modification, improving the affinity of the indigo compound to a substrate, as defined herein, providing an indigo compound that converts to indigo upon removing the modification, or combinations thereof. In some embodiments, the modification is removed by hydrolysis.

[0037] In some embodiments, the modification enhances the aqueous water-solubility of the indigo derivative. The modification is made at any position on the indigo backbone or the indigo derivative. In some embodiments, one or more modification is a substituent on indigo or the indigo derivative. In other embodiments, the substituent is on one or more carbon atom. In further embodiments, the substituent is on one or both nitrogen atom. In yet other embodiments, the substituent is on one or both oxygen atoms. The modification may be selected by one skilled in the art and includes, without limitation, acyl, alkyl, alkoxy, amide, amine, anhydride, aryl, carbamate, CN, cycloalkyl, ester, halide, heteroaryl, heterocyclyl, imine, mesylate, NCh, oxime, sulfonate, tosylate, or urea, wherein each substituent is optionally substituted. In some embodiments, the modification results in an indigo compound which is rotationally symmetrical about an axis. In other embodiments, the modification results in an indigo compound which is rotationally asymmetrical about an axis. However, the modification results in a dye compound that is not the methylsulfonate salt of (E)-3,3'-(3,3'-dioxo-[2,2'-biindoline-l,r-diyl]-l,r- dicarbonyl)bis(l -methylpyridin-l -ium). [0038] The term "wt.%" or "weight%" as used herein refers to the weight of the referenced compound based on the total weight of the solution. For example, the amount of Compound A in an aqueous solution contain 0.01 wt.% of Compound A is based on the based on the total weight of the components in the aqueous solution.

[0039] The term "alkyl" is used herein to refer to both straight- and branched-chain saturated aliphatic hydrocarbon groups. In one embodiment, an alkyl group has 1 to about 10 carbon atoms, i.e., Ci-ioalkyl. In another embodiment, an alkyl group has 1 to about 6 carbon atoms, i.e., Ci-6alkyl. In a further embodiment, an alkyl group has 1 to about 4 carbon atoms, i.e., Ci- 4alkyl. The alkyl may be unsubstituted or substituted as described herein. The substitution may be on any carbon-atom, as permitted by the stability and valency of the substituent. In some examples, the alkyl is a methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, or decyl.

[0040] The term "alkoxy" as used herein refers to the O-(alkyl) group, where the point of attachment is through the oxygen-atom and the alkyl group is defined above. In some examples, the alkyl is a methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, octoxy, nonoxy, or decoxy.

[0041] "Ester" refers to a -COOR group and is bound through the C-atom. R includes, but is not limited to, alkyl, cycloalkyl, aryl, heteroaryl, or heterocyclyl.

[0042] "Acyl" refers to a -C(0)R group which is bound through the C-atom. R includes, but is not limited to, alkyl, cycloalkyl, aryl, heteroaryl, or heterocyclyl.

[0043] "Carboxyl" refers to a -C(0)OH group which is bound through the C-atom.

[0044] " Amine" refers to -Nth, -NHR, or -NR2 which is bound through the N-atom. Each R, independently, includes, but is not limited to, alkyl, cycloalkyl, aryl, heteroaryl, or heterocyclyl.

[0045] "Amide" refers to a -C(0)NR2 group which is bound through the C-atom. Each R, independently, includes, but is not limited to, H, alkyl, cycloalkyl, aryl, heteroaryl, or heterocyclyl.

[0046] "Sulfate" refers to a -SO3R group which is bound through the S-atom. Each R includes, but is not limited to, H, alkyl, cycloalkyl, aryl, heteroaryl, or heterocyclyl.

[0047] "Sulfonate" refers to a -SO2R group which is bound through the S-atom. Each R includes, but is not limited to, H, alkyl, cycloalkyl, aryl, heteroaryl, or heterocyclyl. [0048] "Carbamate" refers to a -0C(0)NR2 group which is bound through the O-atom. Each R, independently, includes, but is not limited to, H, alkyl, cycloalkyl, aryl, heteroaryl, or heterocyclyl.

[0049] "Urea" refers to a -NRC(0)NR2 group which is bound through the N-atom. Each R, independently, includes, but is not limited to, H, alkyl, cycloalkyl, aryl, heteroaryl, or heterocyclyl.

[0050] "Imine" refers to a -C(R)=NR group which is bound through the C-atom. R includes, but is not limited to, H, alkyl, cycloalkyl, aryl, heteroaryl, or heterocyclyl.

[0051] "Oxime" refers to a -C(R)=NOH group which is bound through the C-atom. R includes, but is not limited to, H, alkyl, cycloalkyl, aryl, heteroaryl, or heterocyclyl.

[0052] "Thioether" refers to a -SR group which is bound through the C-atom. R includes, but is not limited to, H, alkyl, cycloalkyl, aryl, heteroaryl, or heterocyclyl.

[0053] "Anhydride" refers to a -C(0)0C(0)R which is bound through the C-atom. R includes, but is not limited to, H, alkyl, cycloalkyl, aryl, heteroaryl, or heterocyclyl.

[0054] The term "halogen" are "halide" are used interchangeably and refer to Cl, Br, F, or I groups.

[0055] "Cycloalkyl" refers to a monocyclic or polycyclic radical that contains carbon and hydrogen, and may be saturated or partially unsaturated. In some embodiments, cycloalkyl groups include 3 to about 12 ring atoms, i.e., C3-i2cycloalkyl. In other embodiments, cycloalkyl groups include 3 to about 8 ring atoms, i.e., C3-8cycloalkyl. In further embodiments, cycloalkyl groups include 5 to about 7 ring atoms, i.e., C5-7cycloalkyl. Examples of cycloalkyl groups include, but are not limited to cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, norbomyl, and the like. The cycloalkyl may be unsubstituted or substituted as described herein. The substitution may be on any carbon-atom, as permitted by the stability and valency of the substituent.

[0056] "Heterocyclyl" refers to a saturated ring that comprises 3 to 12 carbon atom, i.e., C3- heterocyclyl, and from 1 to 6 heteroatoms which are nitrogen, oxygen or sulfur. The heterocyclyl is a monocyclic, bicyclic, tricyclic or tetracyclic ring, which may include fused or bridged ring systems. The heteroatoms in the heterocyclyl may be optionally oxidized. The heterocyclyl may be attached to the rest of the molecule through any atom of the ring(s). In some embodiments, the heterocyclyl has 3 to about 18 ring atoms. In some embodiments, heterocyclyl groups include 4 to about 8 ring atoms. In other embodiments, heterocyclyl groups include 5 to about 7 ring atoms. In some preferred embodiments, the heterocyclyl includes, but are not limited to, dioxolanyl, thienyl[l,3]dithianyl, decahydroisoquinolyl, imidazolinyl, imidazolidinyl, isothiazolidinyl, isoxazolidinyl, morpholinyl, octahydroindolyl, octahydroisoindolyl, 2-oxopiperazinyl, 2-oxopiperidinyl, 2-oxopyrrolidinyl, oxazolidinyl, piperidinyl, piperazinyl, 4-piperidonyl, pyrrolidinyl, pyrazolidinyl, quinuclidinyl, thiazolidinyl, tetrahydrofuryl, trithianyl, monosaccharidyl such as tetrahydropyranyl (glucose), thiomorpholinyl, thiamorpholinyl, l-oxo-thiomorpholinyl, and l,l-dioxo-thiomorpholinyl. The heterocyclyl may be unsubstituted or substituted as described herein. The substitution may be on a carbon-atom or heteroatom, as permitted by the stability and valency of the substituent.

[0057] The term "aryl" refers to 6-15 membered monocyclic, bicyclic, or tricyclic hydrocarbon ring systems, including bridged, spiro, and/or fused ring systems, in which at least one of the rings is aromatic. An aryl group may contain 6 (i.e., phenyl) or about 9 to about 15 ring atoms, such as about 6 to about 8 ring atoms or about 9 to about 11 ring atoms. In some embodiments, aryl groups include, but are not limited to, naphthyl, indanyl, indenyl, anthryl, phenanthryl, fluorenyl, l,2,3,4-tetrahydronaphthalenyl, 6,7,8,9-tetrahydro-5H-benzocycloheptenyl, and 6,7,8,9-tetrahydro-5H-benzocycloheptenyl. The aryl may be unsubstituted or substituted as described herein. The substitution may be on any carbon-atom, as permitted by the stability and valency of the substituent.

[0058] The term "aryloxy" as used herein refers to the O-(aryl) group, where the point of attachment is through the oxygen-atom and the aryl group is defined above. In some examples, the alkyl is a phenoxy or naphthoxy.

[0059] "Heteroaryl" refers to a 5- to l8-membered unsaturated or partially unsaturated radical (e.g., Cs- heteroaryl) that includes one or more ring heteroatoms selected from nitrogen, oxygen and sulfur. In some embodiments, the heteroaryl is monocyclic, bicyclic, tricyclic or tetracyclic. In other embodiments, the heteroatom(s) in the heteroaryl are optionally oxidized. The heteroaryl may be attached to the rest of the molecule through any atom of the ring(s). In some embodiments, the heteroaryl has 3 to about 18 ring atoms. In some embodiments, heteroaryl groups include 4 to about 8 ring atoms. In other embodiments, heteroaryl groups include 5 to about 7 ring atoms. Examples of heteroaryls include, but are not limited to, azepinyl, acridinyl, benzimidazolyl, benzindolyl, l,3-benzodioxolyl, benzofuranyl, benzooxazolyl, benzo[ri]thiazolyl, benzothiadiazolyl, benzo|Z>|| 1.4|dio\epinyl. benzo|Z> || 1.4|o\azinyl. 1,4- benzodioxanyl, benzonaphthofuranyl, benzoxazolyl, benzodioxolyl, benzodioxinyl, benzoxazolyl, benzopyranyl, benzopyranonyl, benzofuranyl, benzofuranonyl, benzofurazanyl, benzothiazolyl, benzothienyl (benzothiophenyl), benzothieno| 3.2-t/| pyrimidinyl. benzotriazolyl, benzo[4,6]imidazo[l,2-a]pyridinyl, carbazolyl, cinnolinyl, cyclopenta[rf]pyrimidinyl, 6,7- dihy dro-5//-cy cl openta| 4.5 |thieno| 2.3-ό/| pyrimidinyl. 5.6-dihydrobenzo|/i|quinazolinyl. 5,6- dihydrobenzo|/7 |cinnolinyl. 6.7-dihydro-5//-benzo|6.7|cyclohepta| l .2- |pyridazinyl. dibenzofuranyl, dibenzothiophenyl, furanyl, furazanyl, furanonyl, furo[3,2-c]pyridinyl, 5.6.7.8.9.1 ()-hexahydrocycloocta|6/|pyrimidinyh 5.6.7.8.9.1 ()-he\ahydrocycloocta|6/|pyridazinyl. 5.6.7.8.9.1 ()-hexahydrocA cloocta|6/|pyridinyl. isothiazolyl, imidazolyl, indazolyl, indolyl, indazolyl, isoindolyl, indolinyl, isoindolinyl, isoquinolyl, indolizinyl, isoxazolyl, 5,8-methano-

5.6.7.8-tetrahydroquinazolinyl, naphthyridinyl, 1 ,6-naphthyridinonyl, oxadiazolyl, 2- oxoazepinyl, oxazolyl, oxiranyl, 5.6.6a.7.8.9.10.1 ()a-octahydrobenzo|/3|quinazolinyh l-phenyl- 1 //-pyrrolyl. phenazinyl, phenothiazinyl, phenoxazinyl, phthalazinyl, pteridinyl, purinyl, pyranyl, pyrrolyl, pyrazolyl, pyrazolo[3,4-cf|pyrimidinyl, pyridinyl, pyrido[3,2-cf]pyrimidinyl, pyri do [3, 4-rf] pyrimidinyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyrrolyl, quinazolinyl, quinoxalinyl, quinolinyl, isoquinolinyl, tetrahydroquinolinyl, 5,6,7,8-tetrahydroquinazolinyl,

5.6.7.8-tetrahydrobenzo|4.5 |thieno|2.3-r/| pyrimidinyl. 6.7.8.9-tetrahydro-5//- cycloheptal 4.5 |thieno| 2.3-r/| pyrimidinyl. 5,6,7,8-tetrahydropyrido[4,5-c]pyridazinyl, thiazolyl, thiadiazolyl, thiapyranyl, triazolyl, tetrazolyl, triazinyl, thieno|2.3-r/| pyrimidinyl. thieno[3,2- d\ pyrimidinyl, thieno[2,3-c]pyridinyl, and thiophenyl (i.e. thienyl). In some embodiments, the heteroaryl is pyridyl. In other embodiments, the heteroaryl is imidazole. The heteroaryl may be unsubstituted or substituted as described herein. The substitution may be on a carbon-atom or heteroatom, as permitted by the stability and valency of the substituent. For example, one N- atom of an imidazole may be substituted. Further, any available carbon-atom may be doubly bonded to an oxygen, i.e., the carbon-atom contains an oxo (=0) group or formyl group (CH=0).

[0060] "Substituted" means that the referenced group may have one or more additional groups, radicals or moieties attached. Such groups include, independently, alkyl, cycloalkyl, aryl, heteroaryl, heterocyclyl, alkoxy, aryloxy, OH, CN, halide, NO2, SO3R (where R is H, halide, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl) such as SO3H or SO3CI, C(0)0R (where R is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl), 0C(0)0R (where R is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl) such as 0C02alkyl, 0C(0)R (where R is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl) such as 0C(0)alkyl, PO3R2 (where R is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl), NR2 (where R is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl), or a quaternary amine such as R = (CH2)zN + (R 10 )3X\ wherein z is 1 or greater (such as z is 1 to 10, 1 to 5, 2 to 10, 2 to 8, or 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10), R 10 is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl, and X is a counteranion as described herein. Examples of R = (CH 2 ) Z N + (R 10 ) 3 X- include, without limitation, R 10 -N(CH 3 ) 3 , R 10 -N(CH2CH 3 ) 3 , R 10 - NH(CH 3 ) 2 , R 10 -NH(CH 2 CH 3 ) 2 , R 10 -NH 2 CH 3 , R 10 -NH 2 (CH 2 CH 3 ), or R 10 -NH 3 . The substituents themselves may be substituted, for example, a cycloalkyl substituent may itself have a halide substituent at one or more of its ring carbons. In some embodiments, the substituents noted above may be further substituted with NR 3 (where R is H, OH, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl) such as N(CH 3 ) 3 or the like. For example, the substituent may be betainyl (0C(0)CH 2 N(CH 3 ) 3 ), cholinyl (OCH 2 CH 2 N(CH 3 ) 3 ), or camitinyl

(0C(0)CH 2 CH(0H)CH 2 N(CH 3 ) 3 ). The term "optionally substituted" means optional substitution with the specified groups, radicals or moieties.

[0061] As used herein, the term "counteranion" as used herein refers to an anion which balances the charge of the base molecule. In some embodiments, any anion which provides a stable salt may be selected. In other embodiments, the anion is acetate, propionate, lactate, citrate, tartrate, succinate, fumarate, maleate, malonate, mandelate, phthalate, Cl, Br, I, F, phosphate, nitrate, sulfate, methanesulfonate, ethanesulfonate, phosphonate, naphthalenesulfonate, benzenesulfonate, toluenesulfonate, camphorsul fon ate, methanesulfate, ethanes ulfate, naphthalenesulfate, benzenes ulfate, toluenesulfate, camphorsulfate, bisulfate, sulfite, or bisulfite.

[0062] In other aspects, the indigo compounds have an affinity to a substrate, as defined herein. The term "affinity to a substrate" as used herein refers to the ability of the dye compound to dye a substrate as described herein as well as leuco-indigo. In some embodiments, the affinity of the indigo compounds to a textile is equal to or within a factor of about 2 to about 3 compared with leuco-indigo. In some embodiments, the affinity is to a textile such as cotton. Such measurements may be made by quantifying the indigo content using post-treatment methods such as sodium hydrosulfite, followed by UV-Vis spectrophotometry as described in Hauser, Improved Determination of Indigo, Textile Chemist and Coloris & American Dyestuff Reporter, 32(2):33, December 2000, which is incorporated herein by reference.

[0063] In further aspects, the indigo compounds convert to indigo upon removing the modification.

[0064] In yet other aspects, the indigo compound is not:

(i) N,N'-dinicotinoyl-[2,2'-biindolinylidene]-3,3'-dione; (i) the N",N"'-methylpyridinium bis(methylsulfate) salt of N,N'-dinicotinoyl-[2,2'- biindolinylidene]-3,3'-dione;

(iii) N,N'-diacetyl-[2,2'-biindobnybdene]-3,3'-dione;

(iv) N,N'-dipropionyl-[2,2'-bi-indobnybdene]-3,3'-dione;

(v) N,N'-di-isobutyryl-[2,2'-biindobnybdene]-3,3'-dione;

(vi) N,N'-dipivaloyl-[2,2'-biindobnybdene]-3,3'-dione;

(vii) N,N'-bis(cyclohexylcarbonyl)-2,2'-bi-indobnylidene-3,3'-dion e;

(viii) N,N'-bis(3-phenylpropionyl)-2,2'-bi-indobnylidene-3,3'-dione ;

(ix) N,N'-bis(ethoxycarbonylacetyl)-2,2'-bi-indolinybdene-3,3'-di one;

(x) N,N'-bis(2-phenylacetyl)-[2,2'-bi-indobnybdene]-3,3'-dione;

(xi) N,N'-bis-(p-methoxyphenylacetyl)2,2'-bi-indobnybdene-3,3'-di one;

(xii) N,N'-bis(l-naphthylacetyl)-2,2'-bi-indobnybdene-3,3'-dione;

(xiii) N,N'-bis(2-phenylbutyryl)-2,2'-indobnyli dene-3, 3'-dione; or

(xiv) (E)-l,r-di(adamantane-l-carbonyl)-[2,2'-biindobnybdene]-3,3' -dione.

[0065] Thus, in some embodiments, the compound is of Formula (I) or a salt thereof.

[0066] R 1 and R 2 may be the same or differ. In some embodiments, one of R 1 and R 2 is H. In further embodiments, one of R 1 and R 2 is SO3H.

[0067] R 1 and R 2 may be, independently, H, SCbR c , SC R c , PCb(R c )2, C(0)-(optionally substituted Ci-9glycolyl), C(0)-(optionally substituted Ci-6alkyl), C(0)-(optionally substituted Ci-6hydroxyalkyl), C(0)0-(optionally substituted Ci-9glycolyl), C(0)-(optionally substituted heteroaryl), C(0)-(optionally substituted aryl), C(0)-(optionally substituted heterocyclyl), C(0)NR A R b , C(0)0-(optionally substituted Ci-6alkyl), C(0)0-(optionally substituted Ci- 6hydroxyalkyl), C(0)0-(optionally substituted heteroaryl), C(0)0-(optionally substituted aryl), or C(0)0-(optionally substituted heterocyclyl). In some embodiments, R 1 and R 2 are, independently, H, SCbR c , SC R 0 , P03(R C )2, C(0)-(optionally substituted Ci-9glycolyl), C(O)- (optionally substituted Ci-6hydroxyalkyl), C(0)-(optionally substituted Ci-9glycolyl), C(O)- (optionally substituted aryl), C(0)-(optionally substituted heterocyclyl), C(0)NR A R B , C(0)0- (optionally substituted Ci-6alkyl), C(0)0-(optionally substituted Ci-6hydroxy alkyl), C(0)0- (optionally substituted heteroaryl), C(0)0-(optionally substituted aryl), or C(0)0-(optionally substituted heterocyclyl).

[0068] In some embodiments, R 1 is C(0)-(optionally substituted alkyl) such as C(0)(Ci-6alkyl substituted with an ester such as C(0)-(Ci-6alkoxy) or C(0)(Ci-6alkyl substituted with aryl such. In other embodiments, R 1 is C(0)-(optionally substituted alkyl) such as C(0)(Ci-6alkyl substituted with an ester such as C(0)methoxy, C(0)propoxy, C(0)butoxy, C(0)pentoxy, or C(O)hexoxy) or C(0)(Ci-6alkyl substituted with an aryl such as phenyl substituted with alkyl, cycloalkyl, aryl, heteroaryl, heterocyclyl, alkoxy, aryloxy, OH, CN, or halide, substituted naphthyl, indanyl, indenyl, anthryl, phenanthryl, fluorenyl, l,2,3,4-tetrahydronaphthalenyl, 6,7,8,9-tetrahydro-5H-benzocycloheptenyl, or 6,7,8,9-tetrahydro-5H-benzocycloheptenyl; C(O)- (C3-6alkyl such as n-propyl, n-butyl, i-butyl, pentyl, or hexyl). In further embodiments, R 1 is C(0)NR A R b , where R A and R B are, independently, H, optionally substituted Ci-6alkyl, optionally substituted Ci-6hydroxy alkyl, or optionally substituted aryl. In still other embodiments, R 1 is C(0)-(optionally substituted heteroaryl). In yet further embodiments, R 1 is C(0)0-(optionally substituted heteroaryl). In other embodiments, R 1 is C(0)-(optionally substituted aryl). In further embodiments, R 1 is C(0)0-(optionally substituted aryl). In yet other embodiments, R 1 is C(0)-(optionally substituted heterocyclyl). In other embodiments, R 1 is SO3H. Preferably, R 1 is C(0)-(optionally substituted pyridyl), such as C(0)-(optionally substituted 2-pyridyl), C(0)-(optionally substituted 3 -pyridyl), or C(0)-(optionally substituted 4- pyridyl). In further embodiments, the pyridyl is substituted with one or more Ci-6alkyl, such as methyl or ethyl. Preferably, the pyridyl is substituted on the N-atom of the pyridyl ring. In other embodiments, R 1 is C(0)-(optionally substituted aryl) such as C(0)-(optionally substituted phenyl). Preferably, the phenyl of the R 1 group is substituted with one or more SO3H, SO3CI, NO2, NH2, OH, halide, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl. In yet further embodiments, R 1 is C(0)NR A R B , wherein one or both of R A and R B is H, optionally substituted Ci-6hydroxyalkyl such as methylhydroxy, ethylhydroxy, propylhydroxy, butylhydroxy, pentylhydroxy, or hexylhydroxy, or optionally substituted Ci-6alkyl such as CH2C(0)0H, CH2CH2C(0)0H, CH2CH2CH2C(0)0H. In still other embodiments, R 1 is C(0)0-(optionally substituted heterocyclyl) such as C(0)0-(optionally substituted succinic anhydride). In further embodiments, R 1 is C(0)0-(optionally substituted alkyl) such as C(0)0(alkyl substituted with heterocyclyl) such as C(0)0(alkyl substituted with a monosaccharide such as glucosyl). In other embodiments, R 1 is C(0)(optionally substituted Ci-6hydroxyalkyl) such as C(0)CH20H, C(0)CH 2 CH 2 0H, C(0)CH0HCH 2 0H, C(0)CH 2 CH0HCH3, or C(0)CH 2 CH0HCH 2 0H. In yet other embodiments, R 1 is C(0)0(optionally substituted Ci-6hydroxy alkyl) such as C(0)0CH 2 0H, C(0)0CH 2 CH 2 0H, C(0)0CH0HCH 2 0H, C(0)0CH 2 CH0HCH 3 , or

C(0)0CH 2 CH0HCH 2 0H. In further embodiments, R 1 is C(0)0(optionally substituted Ci- 9glycol) such as C(0)0CH 2 CH 2 0CH 3 , C(0)(0CH 2 CH 2 ) 2 0CH 3 , or C(0)(0CH 2 CH 2 ) 3 0CH 3 . In still further embodiments, R 1 is S0 3 R c , where R c is H, OH, optionally substituted Ci-6alkyl, optionally substituted C 3 -8cycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, or optionally substituted heterocyclyl such as H, OH, optionally substituted Ci-6alkyl, or optionally substituted aryl. For example, R c in S0 3 R c is OH. In other embodiments, R 1 is S0 2 R c , where R c is H, optionally substituted Ci-6alkyl, optionally substituted C 3 -8cycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, or optionally substituted heterocyclyl such as H, optionally substituted Ci-6alkyl, or optionally substituted aryl. For example, R c in S0 2 R c is aryl substituted with C(0)0H.

[0069] In some embodiments, R 2 is C(0)-(optionally substituted alkyl) such as C(0)(Ci-6alkyl substituted with an ester such as C(0)Ci-6alkoxy). In other embodiments, R 2 is C(0)-(optionally substituted alkyl) such as C(0)(Ci-6alkyl substituted with an ester such as C(0)methoxy, C(0)propoxy, C(0)butoxy, C(0)pentoxy, or C(O)hexoxy) or C(0)(Ci-6alkyl substituted with an aryl such as (phenyl substituted with alkyl, cycloalkyl, aryl, heteroaryl, heterocyclyl, alkoxy, aryloxy, OH, CN, or halide), substituted naphthyl, indanyl, indenyl, anthryl, phenanthryl, fluorenyl, l,2,3,4-tetrahydronaphthalenyl, 6,7,8,9-tetrahydro-5H-benzocycloheptenyl, or 6, 7,8,9- tetrahydro-5H-benzocycloheptenyl; C(0)-(C 3 -6alkyl such as n-propyl, n-butyl, i-butyl, pentyl, or hexyl). In other embodiments, R 2 is C(0)0-(optionally substituted alkyl). In further embodiments, R 2 is C(0)NR A R B , where R A and R B are, independently, H or optionally substituted Ci-6alkyl, or optionally substituted aryl. In still other embodiments, R 2 is C(O)- (optionally substituted heteroaryl). In yet further embodiments, R 2 is C(0)0-(optionally substituted heteroaryl). In other embodiments, R 2 is C(0)-(optionally substituted aryl). In further embodiments, R 2 is C(0)0-(optionally substituted aryl). In yet other embodiments, R 2 is C(0)-(optionally substituted heterocyclyl). In still further embodiments, R 2 is C(0)0-(optionally substituted heterocyclyl). In other embodiments, R 2 is S0 3 H. Preferably, R 2 is C(0)-(optionally substituted pyridyl), such as C(0)-(optionally substituted 2-pyridyl), C(0)-(optionally substituted 3-pyridyl), or C(0)-(optionally substituted 4-pyridyl). In further embodiments, the pyridyl is substituted with one or more Ci-6alkyl, such as methyl or ethyl. Preferably, the pyridyl is substituted on the N-atom of the pyridyl ring. In other embodiments, R 2 is C(0)-(optionally substituted aryl) such as C(0)-(optionally substituted phenyl). Preferably, the phenyl of the R 2 group is substituted with one or more SCbH, SCbCl, N0 2 , NH 2 , OH, halide, alkyl, aryl, cycloalkyl, heteroaryl, heterocyclyl and as substituents. In yet further embodiments, R 2 is C(0)NR A R b , wherein one or both of R A and R B is H, optionally substituted Ci-6hydroxyalkyl such as methylhydroxy, ethylhydroxy, propylhydroxy, butylhydroxy, pentylhydroxy, or hexylhydroxy, or optionally substituted Ci-6alkyl such as CH2C(0)0H, CH2CH2C(0)0H, CH2CH2CH2C(0)0H. In still other embodiments, R 2 is C(0)0-(optionally substituted heterocyclyl) such as C(0)0-(optionally substituted succinic anhydride). In further embodiments, R 2 is C(0)0-(optionally substituted alkyl) such as C(0)0(alkyl substituted with heterocyclyl) such as C(0)0(alkyl substituted with a monosaccharide such as glucosyl). In other embodiments, R 2 is C(0)(optionally substituted Ci-6hydroxyalkyl) such as C(0)CH20H, C(0)CH 2 CH 2 0H, C(0)CH0HCH 2 0H, C(0)CH 2 CH0HCH 3 , or C(0)CH 2 CH0HCH 2 0H. In yet other embodiments, R 2 is C(0)0(optionally substituted Ci-6hydroxy alkyl) such as C(0)0CH 2 0H, C(0)0CH 2 CH 2 0H, C(0)0CH0HCH 2 0H, C(0)0CH 2 CH0HCH 3 , or

C(0)0CH2CH0HCH20H. In further embodiments, R 2 is C(0)0(optionally substituted Ci- 9glycol) such as C(0)0CH 2 CH 2 0CH 3 , C(0)(0CH 2 CH 2 )20CH 3 , or C(0)(0CH 2 CH 2 ) 3 0CH 3 . In still further embodiments, R 2 is S0 3 R c , where R c is H, optionally substituted Ci-6alkyl, optionally substituted C 3 -8cycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, or optionally substituted heterocyclyl such as H, optionally substituted Ci-6alkyl, or optionally substituted aryl. For example, R c in S0 3 R c is aryl substituted with C(0)0H. In other embodiments, R 2 is SC R c , where R c is H, optionally substituted Ci-6alkyl, optionally substituted C 3 -8cycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, or optionally substituted heterocyclyl such as H, optionally substituted Ci-6alkyl, or optionally substituted aryl. For example, R c in SC R 0 is aryl substituted with C(0)0H.

[0070] In certain embodiments, R 3 and R 4 are selected such that they do not affect the properties afforded by the R 1 and/or R 2 groups, i.e., solubility and hydrolysis to name a few. In some embodiments, R 3 and R 4 are, independently, H, halide, optionally substituted Ci-6alkyl, optionally substituted Ci-6alkoxy, S0 3 H, or optionally substituted aryl. In some embodiments, R 3 is halide such as Cl, Br, F, or I. In some embodiments, R 4 is halide such as Cl, Br, F, or I. In other embodiments, R 3 is Ci-6alkyl such as methyl, ethyl, propyl, butyl, pentyl, or hexyl. In further embodiments, R 3 is Ci-6alkoxy, such as methoxy, ethoxy, propoxy, butoxy, pentoxy, or hexoxy. In still other embodiments, R 3 is S0 3 H. In yet further embodiments, R 4 is Ci-6alkyl such as methyl, ethyl, propyl, butyl, pentyl, or hexyl. In other embodiments, R 4 is Ci-6alkoxy, such as methoxy, ethoxy, propoxy, butoxy, pentoxy, or hexoxy. In further embodiments, R 4 is

SO 3 H. [0071] In the structure of Formula (I), m and n are, independently, 0 to 4. In some embodiments, m and n are the same. In other embodiments, m and n differ. In further embodiments, m is 0 In yet other embodiments, n is 0 In still other embodiments, m and n are 1. In yet further embodiments, m and n are 2. In other embodiments, m and n are 3. In further embodiments, m and n are 4.

[0072] In some aspects, R 3 and R 4 are not H, when R 1 and R 2 are both l-methyl-pyrid-3-yl or pyrid-3-yl. However, the compound where R 3 and R 4 are H, when R 1 and R 2 are both l-methyl- pyrid-3-yl or pyrid-3-yl, i.e., the following compounds, may be used in the methods described herein.

(i) N,N'-dinicotinoyl-[2,2'-biindolinylidene]-3,3'-dione;

(i) the N",N"'-methylpyridinium bis(methylsulfate) salt orN.N'-dinicotinoyl-|2.2'- biindolinylidene]-3,3'-dione;

(iii) N,N'-diacetyl-[2,2'-biindolinylidene]-3,3'-dione;

(iv) N,N'-dipropionyl-[2,2'-bi-indolinylidene]-3,3'-dione;

(v) N,N'-di-isobutyryl-[2,2'-biindolinylidene]-3,3'-dione;

(vi) N,N'-dipivaloyl-[2,2'-biindolinylidene]-3,3'-dione;

(vii) N,N'-bis(cyclohexylcarbonyl)-2,2'-bi-indolinylidene-3,3'-dio ne;

(viii) N,N'-bis(3-phenylpropionyl)-2,2'-bi-indolinylidene-3,3'-dion e;

(ix) N,N'-bis(ethoxycarbonylacetyl)-2,2'-bi-indolinylidene-3,3'-d ione;

(x) N,N'-bis(2-phenylacetyl)-[2,2'-bi-indolinylidene]-3,3'-dione ;

(xi) N,N'-bis-(p-methoxyphenylacetyl)2,2'-bi-indolinylidene-3,3'- dione;

(xii) N,N'-bis(l-naphthylacetyl)-2,2'-bi-indolinylidene-3,3'-dione ;

(xiii) N,N'-bis(2-phenylbutyryl)-2,2'-indolinyli dene-3, 3'-dione; or

(xiv) (E)-l,r-di(adamantane-l-carbonyl)-[2,2'-biindolinylidene]-3, 3'-dione.

[0073] In some preferred embodiments, the compound of Formula (I) is Formulae (I-A)-(I-I):

[0074] In these structures, R 5 and R 6 are, independently, H or Ci-6alkyl and X is halide, sulfate, Ci-6alkylsulfate, bisulfate, or phosphate. In some embodiments, R 5 and R 6 are H. In other embodiments, R 5 and R 6 are Ci-6alkyl. In further embodiments, X is halide. In still other embodiments, X is Ci-6alkylsulfate such as MeSC In yet further embodiments, X is bisulfate. In other embodiments, X is phosphate. For the compound of Formula (I-C), both R 5 and R 6 are not CFb when X is CH3SO4 .

[0075] In some embodiments, preferred compounds encompassed by Formula (I) include the following.

[0076] In other preferred embodiments, the compound of Formula (I) is the following:

[0077] wherein X is not CFbSC

[0078] In some preferred embodiments, the compound of Formula (I) is Formulae (I-J)-(I-R):

[0079] In these structures, R 3 and R 4 are, independently, halide, preferably Br, R 5 and R 6 are, independently, H or Ci-6alkyl and X is halide, sulfate, Ci-6alkylsulfate, bisulfate, or phosphate. In some embodiments, R 5 and R 6 are H. In other embodiments, R 5 and R 6 are Ci-6alkyl. In further embodiments, X is halide. In still other embodiments, X is Ci-6alkylsulfate. In yet further embodiments, X is bisulfate. In other embodiments, X is phosphate.

[0080] In other embodiments, preferred compounds encompassed by Formula (I) are the following.

[0081] In the above compounds, X is a counteranion as described herein. In further embodiments, preferred compounds encompassed by Formula (I) include the following or a salt thereof.

[0082] In further embodiments, preferred compounds encompassed by Formula (I) are the following.





[0083] In still further embodiments, preferred compounds encompassed by Formula (I) is of Formula (I-S) or a salt thereof.

[0084] In this structure of Formula (I-S), R 9 and R 10 are, independently alkyl, cycloalkyl, aryl, heteroaryl, heterocyclyl, alkoxy, aryloxy, OH, CN, halide, NO2, SO3R (where R is H, halide, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl) such as SO3H or SO3CI, C(0)OR (where R is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl), OC(0)OR (where R is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl) such as OC02alkyl, OC(0)R (where R is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl) such as OC(0)alkyl, PO3R2 (where R is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl), NR2 (where R is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl), or a quaternary amine, x is 0-5, and y is 0-5. In some embodiments, R 9 and R 10 are SO3H or SO3CI. In other embodiments, R 9 and R 10 are NO2, NH2, OH, halide, Ci-6alkyl, aryl, C3-8cycloalkyl, heteroaryl, or heterocyclyl. In further embodiments, x is 1. In yet other embodiments, y is 1. In still further embodiments, x and y are l.In yet other embodiments, preferred compounds encompassed by Formula (I) are the following or a salt thereof.

[0085] In further embodiments, preferred compounds encompassed by Formula (I) is of Formula (I-T) or a salt thereof.

[0086] In this structure of Formula (I-T), each R c is, independently, H, optionally substituted Ci-6alkyl, optionally substituted C3-scycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, or optionally substituted heterocyclyl. In some aspects, each R c is H, optionally substituted Ci-6alkyl, or optionally substituted aryl. In some aspects, R c is optionally substituted aryl such as optionally substituted phenyl. In further aspects, R c is aryl substituted with C(0)OH.

[0087] In further embodiments, preferred compounds encompassed by Formula (I) is of Formula (I-Tl) or a salt thereof.

[0088] In this structure of Formula (I-Tl), R 9 and R 10 are, independently alkyl, cycloalkyl, aryl, heteroaryl, heterocyclyl, alkoxy, aryloxy, OH, CN, halide, NO2, SO3R (where R is H, halide, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl) such as SO3H or SO3CI, C(0)R (where R is H, NH2, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl), C(0)0R (where R is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl), 0C(0)0R (where R is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl) such as 0C02alkyl, 0C(0)R (where R is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl) such as 0C(0)alkyl, PO3R2 (where R is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl), NR2 (where R is H, alkyl, aryl, cycloalkyl, heteroaryl, or heterocyclyl), or a quaternary amine, x is 0-5, and y is 0-5. In some embodiments, R 9 and R 10 are C(0)0R such as CO2H, C(0)NH2, or NO2. In other embodiments, R 9 and R 10 are Ci-6alkyl. In further embodiments, x is 1. In yet other embodiments, y is 1. In still further embodiments, x and y are 1.

[0089] In some embodiments, a preferred compound encompassed by Formula (I) is the following or a salt thereof:

[0090] In further embodiments, preferred compounds encompassed by Formula (I) is of Formula (I-V) or a salt thereof.

[0091] In this structure of Formula (I-U), each R c is, independently, H, optionally substituted Ci-6alkyl, optionally substituted C3-8cycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, or optionally substituted heterocyclyl such as H, optionally substituted Ci-6alkyl, or optionally substituted aryl. In other aspects, R c is H.

[0092] In some embodiments, a preferred compound encompassed by Formula (I) is the following or a salt thereof.

[0093] In further embodiments, preferred compounds encompassed by Formula (I) is of Formula (I-W) or a salt thereof.

[0094] In this structure of Formula (I-W), one or both of R A and R B is H, optionally substituted Ci-6hydroxyalkyl, optionally substituted Ci-6alkyl, or optionally substituted aryl. In some embodiments, one or both of R A and R B is methylhydroxy, ethylhydroxy, propylhydroxy, butylhydroxy, pentylhydroxy, or hexylhydroxy. In other embodiments, one or both of R A and R B is CH 2 C(0)0H, CH 2 CH 2 C(0)0H, or CH 2 CH 2 CH 2 C(0)0H.

[0095] In further embodiments, preferred compounds encompassed by Formula (I) are the following or a salt thereof.

[0096] In further embodiments, preferred compounds encompassed by Formula (I) is of Formula (I-X) or a salt thereof.

[0097] In this structure of Formula (I-X), one or both R E is H, optionally substituted Ci-6alkyl, Ci-6hydroxyalkyl, optionally substituted aryl, optionally substituted C3-scycloalkyl, optionally substituted heteroaryl, or optionally substituted heterocyclyl. In some aspects, R E is optionally substituted Ci-6alkyl such as C(0)0(alkyl substituted with heterocyclyl), e.g., C(0)0(alkyl substituted with a monosaccharide such as glucosyl). In other aspects, R E is optionally substituted C , hydroxy alkyl such as C(0)0CH20H, C(0)0CH2CH20H, C(0)0CH0HCH20H, C(0)0CH2CH0HCH3, or C(0)0CH2CH0HCH20H. In further aspects, R E is optionally substituted heterocyclyl such as optionally substituted succinic anhydride. In yet other aspects, R E is optionally substituted Ci-9glycol such as C(0)0CH2CH20CH3, CiOXOCFkCFkXOCFb, or C(0)(0CH 2 CH 2 )30CH3.

[0098] In other embodiments, preferred compounds encompassed by Formula (I) are the following or a salt thereof.

[0099] In further embodiments, preferred compounds encompassed by Formula (I) is of Formula (I-Y) or a salt thereof.

[00100] In this structure of Formula (I-X), one or both R E is H, optionally substituted Ci-6alkyl

(such as substituted methyl, n-propyl, substituted i-propyl, alkyl substituted with phenyl substituted with alkyl, cycloalkyl, aryl, heteroaryl, heterocyclyl, alkoxy, aryloxy, OH, CN, or halide), alkyl substituted with naphthyl, alkyl substituted with indanyl, alkyl substituted with indenyl, alkyl substituted with anthryl, alkyl substituted with phenanthryl, alkyl substituted with fluorenyl, alkyl substituted with l,2,3,4-tetrahydronaphthalenyl, alkyl substituted with 6, 7,8,9- tetrahydro-5H-benzocycloheptenyl, or alkyl substituted with 6,7,8,9-tetrahydro-5H- benzocycloheptenyl), optionally substituted Ci-6hydroxyalkyl, optionally substituted heterocyclyl, or optionally substituted Ci-6hydroxyalkyl. In some aspects, R E is optionally substituted Ci-6hydroxyalkyl such as C(0)CH20H, C(0)CH2CH20H, C(0)CH0HCH20H, C(0)CH2CH0HCH3, or C(0)CH2CH0HCH20H. In other aspects, R E is optionally substituted Ci-6alkyl such as Ci-6alkyl substituted with an ester, e.g., C(0)methoxy, C(O)propoxy), C(0)butoxy, C(0)pentoxy, or C(0)hexoxy. [00101] In other embodiments, preferred compounds encompassed by Formula (I) is the following or a salt thereof.

[00102] In further embodiments, the compound is of Formula (II) or a salt thereof:

[00103] In the structure of Formula (II), all of R 1 , R 2 , R 7 , and R 8 are not H. R 1 and R 2 may be the same or different. In some embodiments, R 1 or R 2 is H. In other embodiments, R 1 and R 2 are H.

[00104] R 1 and R 2 are, independently, H, S03R C , S02R C , P03(R C )2, C(0)-(optionally substituted Ci-9glycolyl), C(0)-(optionally substituted Ci-6alkyl), C(0)-(optionally substituted Ci-6hydroxyalkyl), C(0)-(optionally substituted Ci-9glycolyl), C(0)-(optionally substituted heteroaryl), C(0)-(optionally substituted aryl), C(0)-(optionally substituted heterocyclyl), C(0)NR A R b , C(0)0-(optionally substituted Ci-6alkyl), C(0)0-(optionally substituted Ci- 6hydroxyalkyl), C(0)0-(optionally substituted heteroaryl), C(0)0-(optionally substituted aryl), or C(0)0-(optionally substituted heterocyclyl);

[00105] In some embodiments, R 1 is C(0)-(optionally substituted alkyl) such as C(0)(Ci-6alkyl substituted with an ester such as C(0)Ci-6alkoxy). In other embodiments, R 1 is C(0)0- (optionally substituted alkyl). In further embodiments, R 1 is C(0)NR A R B , where R A and R B are, independently, H or optionally substituted Ci-6alkyl, or optionally substituted aryl. In still other embodiments, R 1 is C(0)-(optionally substituted heteroaryl). In yet further embodiments, R 1 is C(0)0-(optionally substituted heteroaryl). In other embodiments, R 1 is C(0)-(optionally substituted aryl). In further embodiments, R 1 is C(0)0-(optionally substituted aryl). In yet other embodiments, R 1 is C(0)-(optionally substituted heterocyclyl). In still further embodiments, R 1 is C(0)0-(optionally substituted heterocyclyl). In other embodiments, R 1 is SCbH. Preferably, R 1 is C(0)-(optionally substituted pyridyl), such as C(0)-(optionally substituted 2-pyridyl), C(0)-(optionally substituted 3-pyridyl), or C(0)-(optionally substituted 4-pyridyl). In further embodiments, the pyridyl is substituted with one or more Ci-6alkyl, such as methyl or ethyl. Preferably, the pyridyl is substituted on the N-atom of the pyridyl ring. In other embodiments, R 1 is C(0)-(optionally substituted aryl) such as C(0)-(optionally substituted phenyl). Preferably, the phenyl of the R 1 group is substituted with one or more SCbH, SO3CI, NO2, NH2, OH, halide, alkyl, aryl, cycloalkyl, heteroaryl, heterocyclyl and as substituents. In yet further embodiments, R 1 is C(0)NR A R b , wherein one or both of R A and R B is H, optionally substituted Ci- 6hydroxyalkyl such as methylhydroxy, ethylhydroxy, propylhydroxy, butylhydroxy, pentylhydroxy, or hexylhydroxy, or optionally substituted Ci-6alkyl such as CH2C(0)0H, CH2CH2C(0)0H, CH2CH2CH2C(0)0H. In still other embodiments, R 1 is C(0)0-(optionally substituted heterocyclyl) such as C(0)0-(optionally substituted succinic anhydride). In further embodiments, R 1 is C(0)0-(optionally substituted alkyl) such as C(0)0(alkyl substituted with heterocyclyl) such as C(0)0(alkyl substituted with a monosaccharide such as glucosyl). In other embodiments, R 1 is C(0)(optionally substituted Ci-6hydroxyalkyl) such as C(0)CH20H, C(0)CH 2 CH 2 0H, C(0)CH0HCH 2 0H, C(0)CH 2 CH0HCH 3 , or C(0)CH 2 CH0HCH 2 0H. In yet other embodiments, R 1 is C(0)0(optionally substituted Ci-6hydroxy alkyl) such as C(0)0CH 2 0H, C(0)0CH 2 CH 2 0H, C(0)0CH0HCH 2 0H, C(0)0CH 2 CH0HCH 3 , or

C(0)0CH2CH0HCH20H. In further embodiments, R 1 is C(0)(optionally substituted Ci- 9glycol) such as C(0)0CH 2 CH 2 0CH 3 , C(0)(0CH 2 CH 2 )20CH 3 , or C(0)(0CH 2 CH 2 ) 3 0CH 3 . In still further embodiments, R 1 is S0 3 R c , where R c is H, optionally substituted Ci-6alkyl, optionally substituted C 3 -8cycloalkyl, optionally subshtuted aryl, optionally substituted heteroaryl, or optionally substituted heterocyclyl such as H, optionally substituted Ci-6alkyl, or optionally substituted aryl. For example, R c in S0 3 R c is aryl subshtuted with C(0)0H. In other embodiments, R 1 is SC R c , where R c is H, optionally substituted Ci-6alkyl, optionally substituted C 3 -8cycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, or optionally substituted heterocyclyl such as H, optionally subshtuted Ci-6alkyl, or optionally subshtuted aryl. For example, R c in SC R 0 is aryl subshtuted with C(0)0H.

[00106] In some embodiments, R 2 is C(0)-(optionally subshtuted alkyl) such as C(0)(Ci-6alkyl subshtuted with an ester such as C(0)Ci-6alkox). In other embodiments, R 2 is C(0)0-(optionally substituted alkyl). In further embodiments, R 2 is C(0)NR A R B , where R A and R B are, independently, H or optionally substituted Ci-6alkyl, or optionally substituted aryl. In still other embodiments, R 2 is C(0)-(optionally substituted heteroaryl). In yet further embodiments, R 2 is C(0)0-(optionally substituted heteroaryl). In other embodiments, R 2 is C(0)-(optionally substituted aryl). In further embodiments, R 2 is C(0)0-(optionally substituted aryl). In yet other embodiments, R 2 is C(0)-(optionally substituted heterocyclyl). In still further embodiments, R 2 is C(0)0-(optionally substituted heterocyclyl). In other embodiments, R 2 is SCbH. Preferably, R 2 is C(0)-(optionally substituted pyridyl), such as C(0)-(optionally substituted 2-pyridyl), C(0)-(optionally substituted 3-pyridyl), or C(0)-(optionally substituted 4-pyridyl). In further embodiments, the pyridyl is substituted with one or more Ci-6alkyl, such as methyl or ethyl. Preferably, the pyridyl is substituted on the N-atom of the pyridyl ring. In other embodiments, R 2 is C(0)-(optionally substituted aryl) such as C(0)-(optionally substituted phenyl). Preferably, the phenyl of the R 2 group is substituted with one or more SCbH, SO3CI, NO2, NH2, OH, halide, alkyl, aryl, cycloalkyl, heteroaryl, heterocyclyl and as substituents. In yet further embodiments, R 2 is C(0)NR A R b , wherein one or both of R A and R B is H, optionally substituted Ci- 6hydroxyalkyl such as methylhydroxy, ethylhydroxy, propylhydroxy, butylhydroxy, pentylhydroxy, or hexylhydroxy, or optionally substituted Ci-6alkyl such as CH2C(0)0H, CH2CH2C(0)0H, CH2CH2CH2C(0)0H. In still other embodiments, R 2 is C(0)0-(optionally substituted heterocyclyl) such as C(0)0-(optionally substituted succinic anhydride). In further embodiments, R 2 is C(0)0-(optionally substituted alkyl) such as C(0)0(alkyl substituted with heterocyclyl) such as C(0)0(alkyl substituted with a monosaccharide such as glucosyl). In other embodiments, R 2 is C(0)(optionally substituted Ci-6hydroxyalkyl) such as C(0)CH20H, C(0)CH 2 CH 2 0H, C(0)CH0HCH 2 0H, C(0)CH 2 CH0HCH 3 , or C(0)CH 2 CH0HCH 2 0H. In yet other embodiments, R 2 is C(0)0(optionally substituted Ci-6hydroxy alkyl) such as C(0)0CH 2 0H, C(0)0CH 2 CH 2 0H, C(0)0CH0HCH 2 0H, C(0)0CH 2 CH0HCH 3 , or

C(0)0CH2CH0HCH20H. In further embodiments, R 2 is C(0)(optionally substituted Ci- 9glycol) such as C(0)0CH 2 CH 2 0CH 3 , C(0)(0CH 2 CH 2 )20CH 3 , or C(0)(0CH 2 CH 2 ) 3 0CH 3 . In still further embodiments, R 2 is S0 3 R c , where R c is H, optionally substituted Ci-6alkyl, optionally substituted C 3 -8cycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, or optionally substituted heterocyclyl such as H, optionally substituted Ci-6alkyl, or optionally substituted aryl. For example, R c in S0 3 R c is aryl substituted with C(0)0H. In other embodiments, R 2 is SC R c , where R c is H, optionally substituted Ci-6alkyl, optionally substituted C 3 -8cycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, or optionally substituted heterocyclyl such as H, optionally substituted Ci-6alkyl, or optionally substituted aryl. For example, R c in SC R 0 is aryl substituted with C(0)0H.

[00107] In some embodiments, R 3 and R 4 are, independently, H, halide, optionally substituted Ci-6alkyl, optionally substituted Ci-6alkoxy, SO3H, or optionally substituted aryl. In some embodiments, R 3 is halide such as Cl, Br, F, or I. In some embodiments, R 4 is halide such as Cl, Br, F, or I. In other embodiments, R 3 is Ci-6alkyl such as methyl, ethyl, propyl, butyl, pentyl, or hexyl. In further embodiments, R 3 is Ci-6alkoxy, such as methoxy, ethoxy, propoxy, butoxy, pentoxy, or hexoxy. In still other embodiments, R 3 is SO3H. In yet further embodiments, R 4 is Ci-6alkyl such as methyl, ethyl, propyl, butyl, pentyl, or hexyl. In other embodiments, R 4 is Ci- 6alkoxy, such as methoxy, ethoxy, propoxy, butoxy, pentoxy, or hexoxy. In further embodiments, R 4 is SO3H.

[00108] In some embodiments, R 7 and R 8 are, independently, H, SCbR 0 , SC R 0 , P03(R C )2, C(0)NR A R b , C(0)-(optionally substituted Ci-6alkyl), C(0)-(optionally substituted aryl), C(O)- (optionally substituted Ci-9glycolyl), C(0)-(optionally substituted Ci-6hydroxyalkyl), C(O)- (optionally substituted heteroaryl), C(0)-(optionally substituted heterocyclyl), C(0)0-(optionally substituted Ci-6alkyl), C(0)0-(optionally substituted aryl), C(0)0-(optionally substituted Ci- 9glycolyl), C(0)0-(optionally substituted Ci-6hydroxyalkyl), C(0)0-(optionally substituted heteroaryl), or C(0)0-(optionally substituted heterocyclyl). Preferably, both R 7 and R 8 are not SO3H. In other embodiments, R 7 and R 8 are, independently, H, SCbR 0 , SC R 0 , P03(R C )2, C(0)NR A R b , C(0)-(optionally substituted Ci-9glycolyl), C(0)-(optionally substituted heteroaryl), C(0)-(optionally substituted heterocyclyl), C(0)-(optionally substituted Ci- 6hydroxy alkyl), C(0)0-(optionally substituted aryl), C(0)0-(optionally substituted Ci-6alkyl), C(0)0-(optionally substituted Ci-9glycolyl), C(0)0-(optionally substituted Ci-6hydroxyalkyl), C(0)0-(optionally substituted heteroaryl), or C(0)0-(optionally substituted heterocyclyl).

[00109] In some embodiments, R 7 and R 8 are, independently, H, SO3H, or C(0)Ci-6alk- C(0)Ci-6alkoxy. In further embodiments, R 7 or R 8 is H. In further embodiments, R 7 and R 8 are H. In other embodiments, R 7 or R 8 is SO3H. In yet further embodiments, R 7 and R 8 are SO3H. In still other embodiment, R7 and R8 are not both when both R 1 and R 2 are H. In further embodiments, R 7 is C(0)Ci-6alk-C(0)Ci-6alkoxy such as C(0)CH2C(0)CH2CH3. In yet other embodiments, R 8 is H. In still further embodiments, R 8 is SO3H. In other embodiments, R 7 is C(0)Ci-6alk-C(0)Ci-6alkoxy such as C(0)CH2C(0)CH2CH3. In still further embodiments, one or both of R 7 and R 8 are C(0)(optionally substituted heteroaryl) such as C(0)(optionally substituted pyridyl). In other embodiments, one or both of R 7 and R 8 are C(0)(optionally substituted Ci-6alkyl) such as C(0)(Ci-6alkyl substituted with C(0)0(Ci-6alkyl) such as C(0)0CH2CH3), C(0)-(substituted methyl), C(0)-(substituted t-butyl), C(0)-(optionally substituted ethyl), C(0)-(unsubstituted propyl), C(0)-(propyl substituted with alkyl, cycloalkyl, heteroaryl, heterocyclyl, alkoxy, aryloxy, OH, CN, or halide), C(0)-(optionally substituted n- butyl), C(0)-(optionally substituted i-butyl), C(0)-(optionally substituted pentyl), or C(O)- (optionally substituted hexyl). Thus, in this example, one of R 7 or R 8 is C(0)Ci-6alkC(0)Ci- 6alkoxy such as C(0)CH2C(0)0CH2CH3 and the other is H. In other examples, R 7 and R 8 is C(0)Ci-6alk-C(0)Ci-6alkoxy such as C(0)CH2C(0)0CH2CH3. In further embodiments, one or both of R 7 and R 8 are C(0)-(optionally substituted aryl) such as C(0)-(phenyl substituted with alkyl, cycloalkyl, aryl, heteroaryl, heterocyclyl, alkoxy, aryloxy, OH, CN, or halide), C(O)- (substituted naphthyl), C(0)-(optionally substituted indanyl), C(0)-(optionally substituted indenyl), C(0)-(optionally substituted anthryl), C(0)-(optionally substituted phenanthryl), C(O)- (optionally substituted fluorenyl), C(0)-(optionally substituted l,2,3,4-tetrahydronaphthalenyl), C(0)-(optionally substituted 6,7,8,9-tetrahydro-5H-benzocycloheptenyl), or C(0)-(optionally substituted 6,7,8,9-tetrahydro-5H-benzocycloheptenyl). For example one or both of R 7 and R 8 is C(0)(phenyl is substituted with CO2H).

[00110] In the structure of Formula (II), m and n are, independently, 0 to 4. In some embodiments, m and n are the same. In other embodiments, m and n differ. In further embodiments, m is 0 In yet other embodiments, n is 0 In still other embodiments, m and n are 1. In yet further embodiments, m and n are 2. In other embodiments, m and n are 3. In further embodiments, m and n are 4.

[00111] In some aspects, the compound of Formula (II) is not:

(i) lH,lH-[2,2'-biindole]-3,3'-diyl diacetate;

(ii) 3,3'-bis(phenylacetoxy)-2,2'-bi-indolyl;

(iii) 3,3'-bis(p-methoxyphenylacetoxy)-2,2'-bi-indolyl;

(iv) 3,3'-bis(l-napthylacetoxy)-2,2'-bi-indolyl;

(v) 3,3'-bis(phenylbutyryloxy)-2,2'-bi-indolyl;

(vi) 3,3'-bis(pivaloyloxy)-2,2'-bi-indolyl;

(vii) 3,3'-bis(l-adamantylcarbonyloxy)-2,2'-bi-indolyl;

(viii) 3,3'-bis(ethoxycarbonylacetoxy)-2,2'-bi-indolyl.

[00112] In further embodiments, preferred compounds encompassed by Formula (II) is of Formula (II-A) or a salt thereof.

[00113] In this structure of Formula (II- A), each R c is, independently, H, optionally substituted Ci-6alkyl, optionally substituted C3-scycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, or optionally substituted heterocyclyl such as H, optionally substituted Ci-6alkyl, or optionally substituted aryl. In some aspects, one R c is H. In further aspects, both R c are H.

[00114] In some embodiments, a preferred compound encompassed by Formula (II) is the following or a salt thereof.

[00115] In further embodiments, a preferred compound encompassed by Formula (II) is of Formula (II-B) or a salt thereof.

[00116] In this structure of Formula (II-B), one or both R E is H, optionally substituted Ci- 6alkyl, or optionally substituted heteroaryl, provided that both R E are not H. In some aspects, one or both R E is optionally substituted Ci-6alkyl such as Ci-6alkyl substituted with an ester. In other aspects, one R E is optionally substituted C(0)Ci-6alk-C(0)Ci-6alkoxy such as C(0)CH2C(0)CH2CH3 and the other is H. In further aspects, both R E are optionally substituted C(0)Ci-6alk-C(0)Ci-6alkoxy such as C(0)CH2C(0)CH2CH3. In yet other aspects, one R E is H. In further aspects, one or both R E is optionally substituted heteroaryl such as optionally substituted pyridyl. In yet other aspects, one or both RE is substituted methyl, ethyl, propyl, n- butyl, substituted t-butyl, i-butyl, pentyl, or hexyl. In further aspects, one or both of R E is substituted phenyl substituted with alkyl, cycloalkyl, aryl, heteroaryl, heterocyclyl, aryloxy, OH, CN, or halide; substituted naphthyl; optionally substituted indanyl; optionally substituted indenyl; optionally substituted anthryl; optionally substituted phenanthryl; optionally substituted fluorenyl; optionally substituted l,2,3,4-tetrahydronaphthalenyl; optionally substituted 6, 7,8,9- tetrahydro-5H-benzocycloheptenyl; or optionally substituted 6,7,8,9-tetrahydro-5H- benzocycloheptenyl.

[00117] In still other embodiments, preferred compounds encompassed by Formula (II) are the following or a salt thereof.

[00118] The compounds discussed above may also be used in the form of salts derived from acceptable acids, bases, alkali metals and alkaline earth metals. Thus, the compounds described herein may exist as the free base or a salt thereof. Preferably, the salts are formed via ionic interactions, covalent interactions, or combinations thereof. For example, the salts may be formed by alkylating a heteroatom such as a N-atom within the compound and having a counteranion ionically bound to the heteroatom. The counteranion may be selected by those skilled in the art and includes those anions from the acids identified above and below.

[00119] The salts can be formed from organic and inorganic acids including, e.g., carboxylic acids such as acetic, propionic, lactic, citric, tartaric, succinic, fumaric, maleic, malic, malonic, mandelic, and phthalic acids, hydrochloric (Cl ), hydrobromic (Br), hydroiodic (G), hydrofluoric (F ), phosphoric, nitric, sulfuric, methanesulfonic, phosphoric, naphthalenesulfonic, benzenes ulfonic, toluenes ulfonic, camphorsulfonic, and similarly known acceptable acids. In some embodiments, the salt is a sulfate salt, alkylsulfate salt, bi sulfate salt, phosphate salt, halide salt, sulfite salt, or bisulfite salt ln further embodiments, the compounds are a sulfate salt. In other embodiments, the compound exists as an alkylsulfate salt such as a methylsulfate or ethylsulfate salt. In further embodiments, the compound exists as a halide salt such as an iodide salt, chloride salt, bromide salt, or fluoride salt. In other embodiments, the compound exists as a bisulfate salt. In yet further embodiments, the compound exists as a phosphate salt.

[00120] In other embodiments, salts may also be formed from inorganic bases, desirably alkali metal salts including, e.g., sodium, lithium, or potassium, such as alkali metal hydroxides. Examples of inorganic bases include, without limitation, sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide.

[00121] Salts may also be formed from organic bases, such as ammonium salts, mono-, di-, and trimethylammonium, mono-, di- and triethylammonium, mono-, di- and tripropylammonium, ethyldimethylammonium, benzyldimethylammonium, cyclohexylammonium, benzyl - ammonium, dibenzylammonium, piperidinium, morpholinium, pyrrolidinium, piperazinium, 1- methylpiperidinium, 4-ethylmorpholinium, 1 -isopropylpyrrolidinium, 1 ,4-dimethylpiperazinium, 1 n-butyl piperidinium, 2-methylpiperidinium, l-ethyl-2-methylpiperidinium, mono-, di- and triethanolammonium, ethyl diethanolammonium, n-butylmonoethanol ammonium, tris(hydroxymethyl)methylammonium, phenylmono-ethanolammonium, diethanolamine, ethylenediamine, choline, betaine, carnitine, and the like. In one example, the base is selected from among sodium hydroxide, lithium hydroxide, potassium hydroxide, and mixtures thereof. [00122] The compounds discussed herein may also encompass tautomeric forms of the structures provided herein, where such forms may be formed.

[00123] Embodiments of modified indigo compounds that have been found particularly useful for the dyeing of textile yams are those that comprise an indigo compound in which at least one of the amine groups is functionalized with an amido-pyridine or a salt thereof. For example, in some embodiments, the modified indigo compound may be selected from a compound having the following base structure, or a salt thereof.

[00124] By the compound having the above-shown base structure, it is meant that each position in the above structure may include additional unshown substituents. For instance, in some embodiments, the nitrogen atom of each pyridine ring may comprise an alkane substituent, such as a methyl group, an ethyl group, or a propyl group, which is represented by Rl and R2 in the structure below. In some embodiments, the salt is formed by the nitrogen atom of the each pyridine ring acting as an anion, with the cation being selected from the group consisting of the halogens (e.g. chlorine, bromine, iodine, methyl chloride, and the like) and the sulfates, such as methyl sulfate, ethyl sulfate, and the like. For example, the anion may comprise one of the following structures.

[00125] Particularly preferred modified indigo compound salts are shown below.

[00126] In addition to being readily convertible to indigo by the mechanisms described herein, each of these compounds has been found to have a particularly beneficial combination of oxygen stability, water stability, and water solubility that make them particularly suitable for dyeing as described herein.

[00127] In some embodiments, a bridge may link the pyridine ring with the rest of the modified indigo compound. For example, in some embodiments, the modified indigo compound may be selected from a compound having the following base structure, or a salt thereof:

in which R 3' and R 4' may be an alkyl group, such as methyl, ethyl, propyl, or the like, or an alkoxide group. By the compound having the above-shown base structure, it is meant that each position in the above structure may include additional unshown substituents. Moreover, in the above structure, the nitrogen atom of each pyridine ring may comprise an alkane substituent, such as a methyl group, an ethyl group, or a propyl group, which is represented by R 1' and R 2' . In other embodiments, R 1' and R 2' in the above structure may simply be hydrogen. In some embodiments, the salt may be formed by the nitrogen atom of each pyridine ring acting as an anion, with the cation being selected from the group consisting of the halogens (e.g. chlorine, bromine, iodine, methyl chloride, and the like) and the sulfates, such as methyl sulfate, ethyl sulfate, and the like.

[00128] In contrast to the structures described above, in which the nitrogen atom of the pyridine ring is in the 3 position, the nitrogen atom of the pyridine ring may also be located in either the 2 or 4 positions. In some embodiments, for instance, the modified indigo compound may be selected from a compound having the following base structure, or a salt thereof:

[00129] As with the above, by the compound having the above-shown base structure, it is meant that each position in the above structure may include additional unshown substituents. For instance, in some embodiments, the nitrogen atom of each pyridine ring may comprise an alkane substituent, such as a methyl group, an ethyl group, or a propyl group, which may be represented by R 1' and R 2' in the above structure. In other embodiments, R 1' and R 2' in the above structure may simply be hydrogen. Moreover, in some embodiments, the bridge linking the pyridine ring with the rest of the modified indigo compound represented by R 3' and R 4' in the above structure may be lacking.

[00130] In other embodiments, R 3' and R 4' may be an alkyl group, such as methyl, ethyl, propyl, or the like, or an alkoxide group. In some embodiments, the salt is formed by the nitrogen atom of each pyridine ring acting as an anion, with the cation being selected from the group consisting of the halogens (e.g. chlorine, bromine, iodine, methyl chloride, and the like) and the sulfates, such as methyl sulfate, ethyl sulfate, and the like. For example, in some embodiments, the modified indigo compound may be selected from the following salts:

[00131] In contrast to the structures described above, in which the nitrogen atom of the pyridine ring is in the 2, 3, or 4 positions, the nitrogen atom of the pyridine ring may also be located in either the 1 or 5 positions. In some embodiments, for instance, the modified indigo compound may be selected from a compound having the following base structure, or a salt thereof:

[00132] Again, by the compound having the above-shown base structure, it is meant that each position in the above structure may include additional unshown substituents. For instance, in some embodiments, the nitrogen atom of each pyridine ring may comprise an alkane substituent, such as a methyl group, an ethyl group, or a propyl group, which may be represented by R 1' and R 2' in the above structure. In other embodiments, R 1' and R 2' in the above structure may simply be hydrogen. Moreover, in some embodiments, the bridge linking the pyridine ring with the rest of the modified indigo compound represented by R 3' and R 4' in the above structure may be lacking. In other embodiments, R 3' and R 4' may be an alkyl group, such as methyl, ethyl, propyl, or the like, or an alkoxide group.

II. Methods of Production

[00133] The compounds described above may be prepared by known chemical synthesis techniques. Among such preferred techniques known to one of skill in the art are included the synthetic methods described in conventional textbooks relating to the construction of synthetic compounds. [00134] The above compounds comprising an indigo compound in which at least one of the amine groups is functionalized with an amido-pyridine or a salt thereof may generally be prepared according to Schemes 1-3.

Scheme 3 [00135] In some embodiments, it may be desirable to dry the modified indigo compound at the conclusion of this process, so as to remove all or substantially all of the water. In doing so, one may prepare a powder comprising the modified indigo compound. This powder may be easily shipped and stored and will not convert to indigo during shipping and/or storage. Moreover, the powder may easily be dissolved at the mill to form the dye. Alternatively, the modified indigo compound may be added to a non-aqueous solvent for shipping and/or storage.

[00136] In some embodiments, the modified indigo compound may be prepared at the mill at which the dyeing occurs and/or immediately before the dyeing process. For instance, in some embodiments, one or more steps in the preparation process may be performed immediately prior to use of the modified indigo compound for dyeing. As an example, the following compound:

may be prepared by contacting the base structure (represented by the following:

with an acid, such as hydrochloric acid. Such a step could easily be performed at the mill and immediately prior to use. This may be particularly beneficial where, for example, the intermediate structure may be more stable and/or easier to store than the modified indigo compound that is used in the dyeing process. III. Compositions Containing the Compound

[00137] Compositions useful herein, in one embodiment, contain a compound discussed above in a diluent. The term "diluent" as used herein refers to a liquid compound that is capable of solubilizing some or all of the compounds discussed herein. In some embodiments, the diluent is water. In other embodiments, the diluent contains water and an organic solvent such as low vapor pressure organic solvents. In further embodiments, the diluent contains an organic solvent. Examples of organic solvents include, without limitation, glycols such as diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, propylene glycol, alcohols such as glycerol, ketones, amines, or combinations thereof.

[00138] The compositions may also include optional suitable inert or inactive ingredients that are useful in compositions for dyeing substrates. The compositions may further include standard dyeing chemicals such as those described in Denim, Manufacture, Finishing and Applications, lst Edition, Ed.: Roshan Paul, Woodhead Publishing, April 23, 2015; Handbook of Textile and Industrial Dyeing, Principles, Processes and Types of Dyes, lst Edition, Ed.: M. Clark, Woodhead Publishing, October 25, 2011; and Handbook of Textile and Industrial Dyeing, Volume 2: Applications of Dyes, lst Edition, Ed.: M. Clark, Woodhead Publishing, October 25, 2011, all of which are incorporated herein by reference.

[00139] In some embodiments, the standard dyeing chemicals prepare the substrate for dyeing, i.e., a pretreating step. In other embodiments, the standard dyeing chemicals are useful in the step of dyeing the substrate. In further embodiments, the standard dyeing chemicals are useful in dyeing denim. In yet other embodiments, the standard dyeing chemicals are useful after dyeing is complete, i.e., a post-treating step such as a hydrolyzing step, neutralizing step, or a rinsing step. These compounds include, without limitation, one or more of an acid, cationic agent, chelating agent, color retention agent, coloring agent, dispersant, foaming agent, mercerization reagent, penetration enhancer, pH buffering agent, salt, stabilizing agent, solubilizing agent, surfactant, thickening agent, tracer, viscosity modifier, or wetting agent. One of skill in the art would be able to determine if a standard dyeing chemical may be used before, during, or after dyeing the substrate.

[00140] In other embodiments, the composition contains a cationic agent. In some embodiments the cationic agent is an ammonium salt such as diallyldimethylammonium chloride, polymerized diallyldimethylammonium chloride, [2-(acryloyloxy)ethyl] trimethylammonium chloride, 3-chloro-2-hydroxylpropyl trimethyl-ammonium chloride, or combinations thereof.

[00141] The composition may further comprise a solubilizing agent. In some embodiments, the solubilizing is an organic solvent, surfactant, or emulsifier. In other embodiments, the organic solvent is a low vapor pressure organic solvent. Examples of organic solvents include, without limitation, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, propylene glycol, glycerol, or combinations thereof. In further embodiments, the surfactant is glyceryl monostearate, polyoxoethylated castor oil, polysorbates such as the Tween® surfactants, sodium lauryl sulfate, sodium dodecyl sulfate, sorbitan esters such as the Span® or Arlacel™ surfactants, stearyl alcohols, cetyl alcohols, triethanolamine, or the Triton™ X-100 surfactant, among others.

[00142] The composition may also contain a stabilizing agent. Such agents may be selected by those skilled in the art and include, without limitation, NaCl, Na 2 S04, a surfactant, or combinations thereof. In some embodiments, the surfactant is glyceryl monostearate, polyoxoethylated castor oil, polysorbates such as the Tween® surfactants, sodium lauryl sulfate, sodium dodecyl sulfate, sorbitan esters such as the Span® or Arlacel™ surfactants, stearyl alcohols, cetyl alcohols, triethanolamine, or the Triton™ X-100 surfactant, among others

IV. Methods of Using the Compounds

[00143] The methods of dyeing described herein are practical and feasible. Thus, the indigo dyeing methods reduce cost, increase throughput and improve the sustainability of the denim dyeing process. In fact, the compounds discussed herein may be utilized in existing plants in place of the currently utilized leuco-indigo methods with little to no change required for the mechanical equipment. The dyeing methods and techniques described herein may selected by those skilled in the art including those recited in Denim, Manufacture, Finishing and Applications, lst Edition, Ed.: Roshan Paul, Woodhead Publishing, April 23, 2015; Handbook of Textile and Industrial Dyeing, Principles, Processes and Types of Dyes, lst Edition, Ed.: M. Clark, Woodhead Publishing, October 25, 2011; and Handbook of Textile and Industrial Dyeing, Volume 2: Applications of Dyes, lst Edition, Ed.: M. Clark, Woodhead Publishing, October 25, 2011, which are herein incorporated by reference. [00144] In some embodiments of the present disclosure, the process of indigo dyeing with a modified indigo compound involves two basic steps. In a first step, a substrate such as a textile yam is contacted with a dye solution that contains a modified indigo compound. As a result of this contact, the substrate takes up an amount of the modified indigo compound. For example, when a cotton yam is contacted with the dye solution, the dye solution both coats a surface of the yam and penetrates some distance below the surface of the yam. The amount of dye solution contained within the resulting yam may be controlled by controlling the duration of the contact and the concentration of modified indigo in the dye solution. When the substrate has been contacted so as to contain a desired amount of dye solution, the dye-treated substrate is brought out of contact with the dye solution.

[00145] The methods are useful in dyeing a substrate by contacting one or more compound described herein with the substrate. The methods are also used in dyeing a substrate by contacting one or more of the compounds described herein or the following compounds with the substrate:

(i) N,N'-dinicotinoyl-[2,2'-biindolinylidene]-3,3'-dione;

(i) the N",N"'-methylpyridinium bis(methylsulfate) salt of N.N'-dinicotinoyl-|2.2'- biindolinylidene]-3,3'-dione;

(iii) N,N'-diacetyl-[2,2'-biindolinylidene]-3,3'-dione;

(iv) N,N'-dipropionyl-[2,2'-bi-indolinylidene]-3,3'-dione;

(v) N,N'-di-isobutyryl-[2,2'-biindolinylidene]-3,3'-dione;

(vi) N,N'-dipivaloyl-[2,2'-biindolinylidene]-3,3'-dione;

(vii) N,N'-bis(cyclohexylcarbonyl)-2,2'-bi-indolinylidene-3,3'-dio ne;

(viii) N,N'-bis(3-phenylpropionyl)-2,2'-bi-indolinyli dene-3, 3'-dione;

(ix) N,N'-bis(ethoxycarbonylacetyl)-2,2'-bi-indolinylidene-3,3'-d ione;

(x) N,N'-bis(2-phenylacetyl)-[2,2'-bi-indolinylidene]-3,3'-dione ;

(xi) N,N'-bis-(p-methoxyphenylacetyl)2,2'-bi-indolinylidene-3,3'- dione;

(xii) N,N'-bis(l-naphthylacetyl)-2,2'-bi-indolinylidene-3,3'-dione ;

(xiii) N,N'-bis(2-phenylbutyryl)-2,2'-indolinyli dene-3, 3'-dione;

(xiv) (E)-l,r-di(adamantane-l-carbonyl)-[2,2'-biindolinylidene]-3, 3'-dione.

(xv) lH,TH-[2,2'-biindole]-3,3'-diyl diacetate;

(xvi) 3,3'-bis(phenylacetoxy)-2,2'-bi-indolyl;

(xvii) 3,3'-bis(p-methoxyphenylacetoxy)-2,2'-bi-indolyl;

(xviii) 3,3'-bis(l-napthylacetoxy)-2,2'-bi-indolyl;

(xix) 3,3'-bis(phenylbutyryloxy)-2,2'-bi-indolyl; (xx) 3,3'-bis(pivaloyloxy)-2,2'-bi-indolyl;

(xxi) 3,3'-bis(l-adamantylcarbonyloxy)-2,2'-bi-indolyl; or

(xxii) 3,3'-bis(ethoxycarbonylacetoxy)-2,2'-bi-indolyl.

[00146] The term "substrate" as used herein refers to a material that may be dyed using the compounds described herein. The substrate contains natural substrates, synthetic substrates, or combinations thereof. In some embodiments, the substrate is natural. In other embodiments, the substrate is synthetic. In further embodiments, the substrate contains natural and synthetic components. The natural substrate may be selected by those skilled in the art from, without limitation, plant or animal substrates. Plant fibers include cotton, kapok, hemp, bamboo, flax, sisal, jute, kenaf, ramie, bamboo, soybean, or coconut, among others. Animal substrates include silk, wool, leather, hair, feather, among others. In some embodiments, the animal substrate is silk, wool, leather, or feather. In other embodiments, the substrate comprises a synthetic fiber such as a synthetic polymer. The synthetic substrate may be prepared using viscose or lyocel processes, preferably or from regenerated/spun cellulose processes. Thus, the synthetic substrate includes, without limitation, rayon such as lyocel (TENCEL®), a polyamide such as nylon, polyester, polyacrylate, polyolefin, or spandex. In some embodiments, the synthetic substrate is a polyamide such as nylon. In other embodiments, the polyester is polyethylene terephthalate. In further embodiments, the polyolefin is polypropylene or polyethylene. In still other embodiments, the polyacrylate is a copolymer of polyacrylonitrile. In contrast to the methods used in the art for dyeing synthetic substrates, the methods described herein do not require heating the substrate, e.g., to the substrate's T g , during the dyeing process.

[00147] While the present disclosure is primarily described in relation to the dyeing of cotton yam, it should be understood that the modified indigo compounds and dyeing processes disclosed herein may also be used to dye any number of different textile materials, including without limitation fibers comprising cellulosic material, such as silk, wool, rayon, lyocel, flax, linen, ramie, and the like, as well as materials comprising combinations thereof.

[00148] The substrate may be in any physical form or shape that permits dyeing by the compounds described herein. Thus, the substrate may be a single fiber or a number of fibers gathered together in another form. In some embodiments, the substrate is in the form of a yam, sheet, or package. In other embodiments, the substrate is a yam. In further embodiments, the substrate is a package. In other embodiments, the substrate is a fabric. The yams may be fitted together to form sheets or packages of yams such as a carpet. Similarly, the fibers may be woven to form a sheet such as a textile. Thus, the substrate may also be woven, knit, or non- woven. In some embodiments, the dye substrate or textile is denim. In further embodiments, the substrate is a fabric or textile such as clothing or garment.

[00149] As used herein, the term "yam" should be understood as meaning a length of interlocked textile fibers or filaments that is suitable for the production of fabrics. In some embodiments, indigo-dyeing is performed on yam or ropes of yam. In other embodiments, the yam is converted to packages, which can be used in weaving or knitting operations. For example, indigo-dyed yam is often weaved into denim fabric, and more specifically this dyed yam is then used as the warp yam in a denim fabric weave. However, in some processes the yam may be weaved into a fabric, such as through a denim weave, and then dyed. Accordingly, unless specified, the term yam should be understood herein as inclusively referring to any of individual yams, ropes of yam, packages of yam, sheets of yam, and yam that is present in a fabric.

[00150] Moreover, as used herein, the term "cotton yam" should be understood as any yam containing cotton fibers. In some embodiments, the cotton yam may contain 100% cotton fibers. In other embodiments, the cotton yam may contain a mixture of cotton fibers and other natural or synthetic fibers/filaments. For example, the cotton yam may contain a blend of cotton and polyester, nylon, elastomeric materials such as elastane (i.e. spandex), or mixtures thereof. Additionally, in some embodiments, a portion of the cotton or all of the cotton may be treated. For example, in some embodiments at least a portion of the cotton may be treated so as to render the cotton hydrophobic. Accordingly, unless specified, the term cotton yam should be understood herein as inclusively referring to any yam that contains cotton fibers, including mixtures of cotton and other materials.

[00151] The term "contacting" as used herein refers to any route by which the substrate is contacted with the dye compound. In some embodiments, the substrate is contacted directly with the compound in the absence of a diluent. In other embodiments, the substrate is contacted with a composition comprising the dye compound. In further embodiments, the substrate is contacted with an aqueous bath comprising the dye compound. In yet other embodiments, the substrate is dipped into an aqueous bath comprising the dye compound. In still further embodiments, the dye compound is in the form of a foam and the foam is applied to the substrate for example by spraying the substrate with the foam. For example, techniques such as The method of any one of the preceding claims, wherein the dyeing comprises dip dyeing, rope dyeing, slasher dyeing, spray dyeing, continuous dyeing, piece dyeing, space dyeing, package dyeing, skein dyeing, garment dyeing, paint brush dyeing, airbrush dyeing, blotch dyeing, foam dyeing, stamping, embossing, brushing, screen printing, digital printing, doctor blading, knife rolling, kiss rolling, or coating may be utilized to contact the substrate with the dye compound.

[00152] Advantageously, the bath containing the dye compound lacks a reducing agent to convert the compound to a leuco form of the compound. In other embodiments, the bath containing the dye compound lacks an alkali agent. In further embodiments, the bath containing the dye compound lacks a reducing agent which is sodium hydrosulfite formamidine sulfmic acid, glucose, sodium borohydride, sodium metabisulfite, thiourea dioxide cellobiose, glyceraldehyde, or fructose.

[00153] When an aqueous bath is utilized to dye the substrate, it is prepared by mixing one or more compound with water. In some embodiments, each bath comprises about 0.5 wt.% to about 70 wt.%, based on the weight of the bath, of the compound. In other embodiments, the bath comprises about 1 wt.% to about 50 wt.%, based on the weight of the bath, of the compound. In further embodiments, the bath comprises about 2 wt.% to about 30 wt.%, based on the weight of the bath, of the compound. In still other embodiments, the bath contains about 5 to about 25 wt.%, based on the weight of the bath, of the compound. In yet further embodiments, the bath contains about 10 to about 20 wt.%, based on the weight of the bath, of the compound. In other embodiments, the bath contains about 12 to about 18 wt.%, based on the weight of the bath, of the compound. In further embodiments, the bath contains about 14 to about 16 wt.%, based on the weight of the bath, of the compound. Preferably, the bath contains about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,

29, or 30 wt.%, based on the weight of the bath, of the compound. More preferably, each bath contains about 1 to about 3 wt.% to about 70 wt.%, based on the weight of the bath, of the compound. Even more preferably, each bath contains about 2 wt.% to about 70 wt.%, based on the weight of the bath, of the compound.

[00154] In addition to the compound and water, the aqueous bath may contain other additional components such as those described above for compositions containing the compound. These compounds include, without limitation, an acid, cationic agent, caustic agent, chelating agent, color retention agent, coloring agent, dispersant, foaming agent, hydrolyzing agent, mercerization reagent, penetration enhancer, pH buffering agent, salt, solubilizing agent, stabilizing agent, surfactant, thickening agent, tracer, viscosity modifier, wetting agent, or combinations thereof. One of skill in the art would be able to determine if a standard dyeing chemical may be used before, during, or after dyeing the substrate. In some embodiments, the aqueous bath lacks a solubilizing agent. In other embodiments, the aqueous bath contains solubilizing agent. In further embodiments, the aqueous bath is acidic, i.e., has a pH of less than about 7. In some embodiments, the aqueous bath as a pH of about 0.5 to about 7, about 1 to about 7, about 1 to about 6, about 1 to about 5, about 1 to about 4, about 1 to about 3, about 1 to about 2, about 1, about 2, about 3, about 4, about 5, about 6, or about 6.

[00155] The substrate is kept in contact with the aqueous solution, i.e., dyed, for a time sufficient so as to dye the substrate. In some embodiments, the time is dependent on the extent of dye that penetrates the substrate. In other embodiment, the time is dependent on the desired color of the substrate is achieved. In further embodiments, the time is dependent on the concentration of the dye being applied to the substrate. In yet other embodiments, the substrate is kept in contact with the aqueous solution for about 5 seconds to about 10 hours. In still further embodiments, the substrate is kept in contact with the dye compound for about 5, 10, 20, 30, or 45 seconds, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 30, or 45 minutes, or 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 hours.

[00156] The substrate also is kept in contact with the aqueous solution at a suitable temperature. In some embodiments, the dyeing temperature is any temperature that does not degrade any components of the dyeing process. In some embodiments, the temperature is ambient temperature. In other embodiments, the temperature is about 20 to about 40°C, such as about 10 to about 35°C, or about room temperature.

[00157] In another step, the modified indigo compound that has been taken up by the dye- treated substrate is converted to indigo through a process of hydrolysis. In some embodiments, the substrate is contacted with a hydrolyzing agent, the hydrolyzing agent being capable of reacting with the modified indigo compound contained within the substrate to convert the modified indigo compound into indigo. For example, when a cotton yam that has been contacted with a dye solution is then contacted with an appropriate hydrolyzing agent, the modified indigo contained within the cotton yam is converted to indigo, thereby producing an indigo-dyed yam.

[00158] In some embodiments, the substrate may be contacted with an alkali agent in order to hydrolyze the modified indigo compound so as to convert it into indigo. The contacting of the substrate with the alkali hydrolyzing agent may be performed in a number of different manners. For instance, the substrate may be dipped in a solution containing the alkali agent, e.g. an aqueous hydrolyzing bath, or a solution containing the alkali agent may be sprayed onto the substrate. By converting the modified indigo compound into indigo, an indigo-dyed substrate is produced. [00159] In many dyeing processes, multiple iterations of this two-step process will be necessary in order to obtain a desirable shade of indigo. Accordingly, in many dyeing processes, once the modified indigo compound on the substrate is converted into indigo, the substrate will again be contacted with dye solution containing a modified indigo compound. In some embodiments, substrate is contacted with the same bath that was used to as the initial dye bath. In other embodiments, the substrate is contacted with another dye bath containing the same or a different amount of the dye compound. One of skill in the art would be able to determine how many instances it is necessary to contact the substrate with the dye compound. For example, one skilled in the art would be able to determine how many times to dip the substrate into the dye bath. See, for example, Denim, Manufacture, Finishing and Applications, lst Edition, Ed.: Roshan Paul, Woodhead Publishing, April 23, 2015; Handbook of Textile and Industrial Dyeing, Principles, Processes and Types of Dyes, lst Edition, Ed.: M. Clark, Woodhead Publishing, October 25, 2011; and Handbook of Textile and Industrial Dyeing, Volume 2: Applications of Dyes, lst Edition, Ed.: M. Clark, Woodhead Publishing, October 25, 2011, all of which are incorporated herein by reference for these teachings. Although the substrate may only require contacting it once with the dye compound, the substrate typically is contacted with the dye compound at least two times. In some embodiments, the dye compound is contacted about 4 to about 25 times, about 5 to about 20 times, about 6 to about 18 times, about 7 to about 16 times, about 8 to about 14 times, about 8 to about 12 times, about 8 to 10 times, about 9 to 16 times, about 9 to about 14 times, about 9 to about 12 times, about 12 to about 18 times, about 12 to about 16 times, 1 to about 25 times, 2 to about 20 times, about 3 to about 18 times, about 4 to about 16 times, about 5 to about 15 times, about 5 to about 12 times, about 5 to about 10 times, about 5 to about 8 times, or any other ranges there between.

[00160] A further step includes hydrolyzing the dye compound in the dyed substrate to indigo. In some embodiments, hydrolysis of the dye compound is performed with a solution which contains water. In other embodiments, hydrolysis is performed with water. The water can be from a fresh source or may be reused. Thus, the water can contain other components including, without limitation, an acid, cationic agent, chelating agent color retention agent, coloring agent, dispersant, foaming agent, mercerization reagent, organic solvent, pH buffering agent, penetration enhancer, salt, stabilizing agent, solubilizing agent, surfactant, thickening agent, tracer, viscosity modifier, or wetting agent. In some embodiments, the rinse water contains an acid, cationic agent, chelating agent, dispersant, foaming agent, organic solvent, pH buffering agent, penetration enhancer, salt, solubilizing agent, surfactant, thickening agent, tracer, viscosity modifier, or wetting agent. [00161] The application of heat to the dye-treated yam triggers the hydrolysis of the modified indigo compound, decreasing the time necessary for conversion to indigo to occur. In some embodiments, for example, the application of heat may be controlled to convert the modified indigo compound into indigo in less than 15 minutes, less than 10 minutes, less than 8 minutes, less than 6 minutes, less than 5 minutes, less than 3 minutes, about 5 seconds to about 5 minutes, about 0.5 minutes to about 2 minutes, about 1 minute to about 5 minutes, about 2 minutes to about 5 minutes, about 1 minute to about 4 minutes, about 10 seconds to about 5 minutes, about 20 seconds to about 5 minutes, about 30 seconds to about 5 minutes, or about 45 seconds to about 5 minutes, among others.

[00162] As discussed above, the hydrolysis may be performed using lower temperatures than those utilized in the art. Thus, in some embodiments, the hydrolysis may be performed using heat such as by contacting the dyed substrate with a heat plate or blowing hot air on the dyed substrate. One skilled in the art would be able to select a suitable temperature for use in the hydrolysis of the dye compound. For example, the heat comprises a temperature of about 20 to about 80°C, such as about 30 to about 80°C, about 40 to about 80°C, about 50 to about 80°C, about 60 to about 80°C, about 70 to about 80°C, about 20 to about 70°C, about 20 to about 60°C, about 20 to about 50°C, about 20 to about 40°C, or about 20, 30, 40, 50, 60, 70, or about 80°C.

[00163] After the hydrolysis is complete, additional dyeing steps and hydrolysis steps may be utilized until the desired dye penetration or color is attained by the substrate. It may also be desirable to dry the dyed substrate prior to hydrolyzing. Thus, in some embodiments, the substrate is dyed as described herein, dried, and hydrolyzed as described herein. In some embodiments, the dyeing step is repeated 1 to about 50, 2 to about 30, 5 to about 25, 10 to about 20, or 1 to about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 times. Similarly, the hydrolysis step may be repeated the same number of times that the dyeing step is repeated. In some embodiments, the hydrolysis is repeated 1 to about 50, 2 to about 30, 5 to about 25, 10 to about 20, or 1 to about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 times.

[00164] The dyeing is performed until the desired color of the substrate is reached. The desired color may be determined by one skilled in the art using techniques and instruments such as color spectrophotometers.

[00165] Following dyeing and hydrolyzing, the substrate may be rinsed using techniques known to those skilled in the art. Similarly, the rinsing step may be performed between one or more of the dyeing and hydrolyzing steps. Preferably, one or more rinsing steps are performed after all dyeing and hydrolyzing steps are complete. However, a rinsing step may not be required. In situations where a rinsing step is performed, it may be is repeated 1 to about 50, 2 to about 30, 5 to about 25, 10 to about 20, or 1 to about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 times.

[00166] Before the substrate is again contacted with the dye solution, however, it may be desirable to rinse the indigo-dyed substrate. Accordingly, in some embodiments, the process may include a third step, the third step being rinsing the indigo dyed yam. The rinsing step may comprise simply contacting the indigo-dyed yam with water.

[00167] The dyeing of a cotton yam by the improved process disclosed herein may be performed by a variety of dyeing methods. In some embodiments, for example, the dyeing may be performed using a modified dipping process. The modified dipping process may be performed in largely the same manner as the conventional dipping process that is employed for the indigo dyeing of cotton yams. In this process, one or more yams continuously travel such that each yam enters a dye bath at a first end and exits the dye bath at the second end. This process is known as dipping. The length of time that a particular portion of the yam spends in the dye bath may be carefully controlled to provide for a desirable uptake of the indigo precursor. In the conventional process, once the dye-treated yam exits the dye bath, the leuco-indigo quickly converts to indigo during a short period in which the yam is exposed to air. The one or more yams may continuously travel through a series of dye baths and subsequent air exposures in order to obtain a desired shade of indigo.

[00168] In embodiments of the present process, the leuco-indigo dye bath may be replaced with a dye bath containing a modified indigo compound according to the various embodiments described herein. For instance the dye bath may generally comprise an aqueous solution of the modified indigo compound. In addition to water and the modified indigo compound, the dye bath may also contain one or more of the following: wetting agents, thickening agents, chelating agents, pH buffering agents, and stabilizers. Notably, as described above, in many embodiments the dye bath containing the modified indigo compound may not contain a reducing agent. In some embodiments, therefore, the dye bath may consist essentially of water and the modified indigo compound. Additionally, because the modified indigo compound does not require strong reducing agents and a high pH environment to maintain stability, embodiments of the dye bath may have a pH of less than 9, alternatively less than 8, alternatively less than 7. In some embodiments, it may be desirable that the dye bath be about neutral, i.e. have a pH of about 7. [00169] Additionally, rather than simply exposing the dye-treated yams to air, the dye-treated yam may be subjected to a treatment that is effective to more efficiently convert the modified indigo compound into indigo, such as those described herein. Importantly, the one or more yams may continuously through a series of dye baths in order to obtain a desired shade of indigo in much the same way as in the conventional process. Accordingly, it is believed that large-scale commercial dyeing equipment might easily be converted to utilize the improved dyeing process disclosed herein without the need for major expenditures of capital.

[00170] In some embodiments, the dyeing may be performed by a foam-dyeing process, in which a foam containing the modified indigo compound may be contacted with a yam as the yam travels through a dyeing chamber. Because of the oxygen stability of embodiments of the modified indigo compounds, the atmosphere in the dyeing chamber may contain oxygen. For instance, in some embodiments, the dyeing chamber may contain air. It is also possible to carefully control the depth of the dye penetration into the yam using the foam dyeing process.

[00171] In other embodiments, the dyeing may be performed by alternative methods, such as by spraying, painting, bmshing, rolling, and/or printing the dye (e.g. an aqueous solution containing the modified indigo compound) onto the yam. In some embodiments, dyeing is performed using spraying. In further embodiments, dyeing is performed using painting. In other embodiments, dyeing is performed using brushing. In still further embodiments, dyeing is performed using rolling. In yet other embodiments, dyeing is performed using printing such as digital printing, or screen printing.

[00172] In some embodiments, the substrate such as cotton yam may be pretreated using an anti-migrant, pH buffering agent, anionic agent, hydrolysis catalyst, or alkali agent prior to being contacted with the dye containing the modified indigo compound. The particular anti-migrant, pH buffering agent, anionic agent, hydrolysis catalyst or alkali agent may be readily selected by one skilled in the art from such reagents that may be utilized to prepare the substrate for dyeing. In some embodiments, the pretreating is performed using a carboxylate salt, phosphate salt, sodium salt of polyacrylic acid, derivative of polyacrylate, copolymer of polyacrylate, polymaleic acid, sodium bicarbonate, sodium carbonate, sodium citrate, sodium citrate dibasic, tartrate salts, succinate salts, malonate salts, polymers comprising phosphate groups, or polymers comprising polyphosphate groups. See, e.g., the buffers described in htps://www.sigmaaldrich.com/life-science/core-bioreagents/bi ological-buffers/leaming- center/huffer-reference-cen ter.html. which is incorporated by reference. [00173] Examples of alkali agents include inorganic alkalis, such as hydroxides such as sodium hydroxide, or potassium hydroxide, carbonates such as sodium carbonate, and the like, or organic alkalis, including members of the amine family such as diethanolamine, trimethylamine, hexamethylenediamine, liquid ammonia, and the like, or combinations thereof.

[00174] Examples of carboxylate salts include, without limitation, sodium acetate, sodium stearate, or a salt of lactic acid.

[00175] Examples of phosphate salts include, without limitation, sodium phosphate dibasic, sodium phosphate monobasic, or sodium pyrophosphate.

V. Kits Containing the Compound

[00176] Also provided are kits comprising one or more dye compound described herein and a device that provides the heat required to convert the compound to indigo. Advantageously, because the above-described compounds are stable in a dried state, they can more easily be transported and/or stored for future use.

[00177] The kits may also include one or more of the anti-migrant, pH buffering agent, anionic agent, hydrolysis catalyst, or alkali agent as described herein.

[00178] It can be seen that the described embodiments provide unique and novel modified indigo compounds and a unique and novel process for dyeing a substrate, such as cotton yam, using modified indigo compounds, each of which having a number of advantages over those in the art. While there is shown and described herein certain specific structures embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.

[00179] The following Examples are provided to illustrate some of the concepts described within this disclosure. While each Example is considered to provide specific individual embodiments of composition, methods of preparation and use, none of the Examples should be considered to limit the more general embodiments described herein.

[00180] In the following examples, efforts have been made to ensure accuracy with respect to numbers used (e.g. amounts, temperature, etc.) but some experimental error and deviation should be accounted for. Unless indicated otherwise, temperature is in degrees C, pressure is at or near atmospheric.

[00181] VI. Aspects

Aspect 1. A method for dyeing a substrate, comprising:

(i) pretreating the substrate;

(ii) dyeing the substrate with a dye compound comprising an indigo derivative, or a salt thereof, having one or more modification over the chemical structure of indigo, wherein the indigo derivative has a water-solubility of greater than 0.2% w/v in the absence of a reducing agent and in the presence oxygen, and converts to indigo upon removing the modification, wherein the chemical structure of indigo is the following:

(iii) hydrolyzing the substrate at a temperature of about 20 to about 80°C.

Aspect 2. The method of Aspect 1, wherein the one or more modification enhances the aqueous solubility of the dye compound lacking the modification.

Aspect 3. The method of Aspect 1 or 2, wherein the one or more modification is a

substituent on indigo or the indigo derivative.

Aspect 4. The method of Aspect 2 or 3, wherein the substituent is on one or both nitrogen atoms.

Aspect 5. The method of Aspect 2 or 3, wherein the substituent is on one or more carbon atom.

Aspect 6. The method of Aspect 2 or 3, wherein the substituent is on one more both oxygen atoms.

Aspect 7. The method of any one of Aspects 3-6, wherein the substituent is an alkyl,

cycloalkyl, alkoxy, halide, acyl, amine, ester, amide, aryl, heteroaryl, heterocyclyl, sulfonate, carbamate, urea, imine, oxime, anhydride, CN, NCh, mesylate, or tosylate, wherein each is optionally substituted. Aspect 8. The method of any one of Aspects 1-7, wherein the reducing agent is sodium hydrosulfite, formamidine sulfmic acid, glucose, sodium borohydride, sodium

metabisulfite, thiourea dioxide, cellobiose, glyceraldehyde, or fructose.

Aspect 9. The method of any one of the preceding Aspects, wherein the compound is of Formula (I) or (II):

wherein:

R 1 and R 2 are, independently, H, SCbR 0 , SC R 0 , PCb(R c )2, C(0)NR A R B , C(O)-

(optionally substituted Ci-6alkyl), C(0)-(optionally substituted aryl), C(0)-(optionally substituted Ci-9glycolyl), C(0)-(optionally substituted heteroaryl), C(0)-(optionally substituted heterocyclyl), C(0)-(optionally substituted Ci-6hydroxyalkyl), C(0)0- (optionally substituted Ci-6alkyl), C(0)0-(optionally substituted aryl), C(0)0- (optionally substituted Ci-9glycolyl), C(0)0-(optionally substituted Ci- 6hydroxyalkyl), C(0)0-(optionally substituted heteroaryl), C(0)0-(optionally substituted heterocyclyl); or

R 3 and R 4 are, independently, H, halide, optionally substituted Ci-6alkyl, optionally substituted Ci-6hydroxyalkyl, optionally substituted Ci-6alkoxy, optionally substituted aryl, or SO3H;

R 7 and R 8 are, independently, H, SCbR 0 , SC R 0 , P03(R C )2, C(0)NR A R B , C(O)-

(optionally substituted Ci-6alkyl), C(0)-(optionally substituted aryl), C(0)-(optionally substituted Ci-9glycolyl), C(0)-(optionally substituted Ci-6hydroxyalkyl), C(O)- (optionally substituted heteroaryl), C(0)-(optionally substituted heterocyclyl), C(0)0-(optionally substituted Ci-6alkyl), C(0)0-(optionally substituted aryl), C(0)0-(optionally substituted Ci-9glycolyl), C(0)0-(optionally substituted Ci- 6hydroxyalkyl), C(0)0-(optionally substituted heteroaryl), or C(0)0-(optionally substituted heterocyclyl);

R A and R B are, independently, H or optionally substituted Ci-6alkyl, or optionally substituted aryl; R c is H, optionally substituted Ci-6alkyl, optionally substituted C3-scycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, or optionally substituted heterocyclyl;

m and n are, independently, 0 to 4;

or a salt thereof.

Aspect 10. The method of Aspect 9, wherein when the compound is of Formula (I), R 3 and R 4 are not H, when R 1 and R 2 are both l-methyl-pyridyl-3-yl.

Aspect 11. The method of Aspect 9 or 10, wherein m is 0.

Aspect 12. The method of any one of Aspects 9-11, wherein n is 0.

Aspect 13. The method of Aspect 9 or 10, wherein R 3 is a halide.

Aspect 14. The method of any one of Aspects 9, 10, or 13, wherein R 4 is a halide.

Aspect 15. The method of any one of Aspects 9, 10, or 14, wherein R 3 is Ci-6alkyl.

Aspect 16. The method of any one of Aspects 9, 10, 13, or 15, wherein R 4 is Ci-6alkyl.

Aspect 17. The method of any one of Aspects 9-16, wherein one of R 1 or R 2 is H.

Aspect 18. The method of any one of Aspects 9-17, wherein one of R 1 and R 2 is SO3H.

Aspect 19. The method of any one of Aspects 9-18, wherein the compound is of Formula (I):

Aspect 20. The method of any one of Aspects 9-19, wherein one or both of R 1 and R 2 is

C(0)-(optionally substituted heteroaryl).

Aspect 21. The method of any one of Aspects 9-20, wherein one or both of R 1 and R 2 is C(0)-(optionally substituted pyridyl), such as C(0)-(optionally substituted 2-pyridyl), C(0)-(optionally substituted 3-pyridyl), or C(0)-(optionally substituted 4-pyridyl).

Aspect 22. The method of Aspect 21, wherein the pyridyl is substituted with Ci-6alkyl. Aspect 23. The method of Aspect 21 or 22, wherein the pyridyl is substituted with one or more methyl or ethyl.

Aspect 24. The method of any one of Aspects 21-23, wherein the pyridyl is substituted on the N-atom.

Aspect 25. The method of any one of Aspects 9-19, wherein one or both of R 1 and R 2 is C(0)-(optionally substituted aryl), such as C(0)-(optionally substituted phenyl).

Aspect 26. The method of any one of Aspects 9-19, wherein one or both of R 1 and R 2 is C(0)NR A R b , wherein one or both of R A and R B is H, optionally substituted Ci- 6hydroxyalkyl, or optionally substituted Ci-6alkyl.

Aspect 27. The method of any one of Aspects 9-19, wherein one or both of R 1 and R 2 are C(0)0-(optionally substituted heterocyclyl) such as C(0)0-(optionally substituted pyrrolidone).

Aspect 28. The method of any one of Aspects 9-19, wherein one or both of R 1 and R 2 are, independently, C(0)0-(optionally substituted alkyl) such as C(0)0(alkyl substituted with heterocyclyl) such as C(0)0(alkyl substituted with glucosyl).

Aspect 29. The method of any one of Aspects 9-19, wherein one or both of R 1 and R 2 are, independently, C(0)(optionally substituted Ci-6hydroxyalkyl).

Aspect 30. The method of any one of Aspects 9-19, wherein one or both of R 1 and R 2 are, independently, C(0)0(optionally substituted Ci-6hydroxy alkyl).

Aspect 31. The method of any one of Aspects 9-19, wherein one or both of R 1 and R 2 are, independently, C(0)(optionally substituted Ci-9glycol).

Aspect 32. The method of any one of Aspects 9-18, wherein the compound is of Formula

Aspect 33. The method of Aspect 32, wherein one or both of R 1 and R 2 are H. Aspect 34. The method of Aspect 32 or 33, wherein one or both of R 7 and R 8 are H.

Aspect 35. The method of Aspect 32 or 33, wherein one of R 7 and R 8 are SCbH.

Aspect 36. The method of Aspect 32 or 33, wherein one or both of R 7 and R 8 are C(0)(optionally substituted heteroaryl) such as C(0)(optionally substituted pyridyl).

Aspect 37. The method of Aspect 32 or 33, wherein one or both of R 7 and R 8 are C(0)(optionally substituted Ci-6alkyl).

Aspect 38. The method of Aspect 37, wherein the Ci-6alkyl is substituted with C(0)0(Ci- 6alkyl) such as C(0)0CH2CH3.

Aspect 39. The method of Aspect 32 or 33, wherein one or both of R 7 and R 8 are C(O)- (optionally substituted aryl) such as C(0)-(optionally substituted phenyl).

Aspect 40. The method of Aspect 39, wherein the phenyl is substituted with CO2H.

Aspect 41. The method of any one of the preceding Aspects which is an acid or base addition salt.

Aspect 42. The method of any one of the preceding Aspects, which is a sulfate salt, alkylsulfate salt, bisulfate salt, phosphate salt, or halide salt.

Aspect 43. The method of Aspect 42, wherein the halide salt is an iodide salt, chloride salt, bromide salt, or fluoride salt.

Aspect 44. The method of Aspect 42, wherein the compound is an alkylsulfate salt.

Aspect 45. The method of Aspect 44, wherein the compound is a methylsulfate or ethylsulfate salt.

Aspect 46. The method of Aspect 9 or 10, wherein the compound is of Formula (IA):

wherein:

R 5 and R 6 are, independently, H or Ci-6alkyl; and

X is halide, sulfate, Ci-6alkylsulfate, bisulfate, or phosphate;

with the proviso that both R 5 and R 6 are not CFb when X is CFbSOT.

Aspect 47. The method of Aspect 9, wherein the compound is of Formula (IB) or (IC):

wherein:

R 5 and R 6 are, independently, H or Ci-6alkyl; and

X is halide, sulfate, Ci-6alkylsulfate, bisulfate, or phosphate. Aspect 48. The method of Aspect 9, wherein the compound is:

wherein X is a counteranion.

Aspect 49. The method of Aspect 9, wherein the compound is:

wherein X is acetate, propionate, lactate, citrate, tartrate, succinate, fumarate, maleate, malonate, mandelate, phthalate, Cl, Br, I, F, phosphate, nitrate, sulfate, ethanes ulfonate, phosphonate, naphthalenesulfonate, benzenesulfonate, toluenesulfonate, camphorsulfonate, methanes ulfate, ethanes ulfonate, naphthalenes ulfate, benzenesulfate, toluenesulfate, camphorsulfate, bisulfate, sulfite, or bisulfite.

Aspect 50. The method of Aspect 9, wherein the compound is:

wherein, X is a counteranion. Aspect 51. The method of Aspect 9, wherein the compound is:

Aspect 52. The method of Aspect 9, wherein the compound is:

Aspect 53. The method of Aspect 9, wherein the compound is: or salt thereof.

Aspect 54. The method of Aspect 9, wherein the compound is: or a salt thereof.

Aspect 55. The method of Aspect 9, wherein the compound is:

, or a salt thereof.

Aspect 56. The method of Aspect 9, wherein the compound is: or a salt thereof.

Aspect 57. The method of Aspect 9, wherein the compound is:

or a salt thereof.

Aspect 58. The method of any one of the preceding Aspects, wherein the compound converts to indigo through hydrolysis.

Aspect 59. The method of any one of the preceding Aspects, wherein the compound is substantially stable in the presence of oxygen such as in aqueous solutions.

Aspect 60. The method of any one of the preceding Aspects, wherein the compound has greater water solubility than indigo.

Aspect 61. The method of any one of the preceding Aspects, wherein the compound is mixed with water.

Aspect 62. The method of Aspect 61, wherein the water is acidic.

Aspect 63. The method of Aspect 61 or 62, wherein the water further comprises one or more additional components.

Aspect 64. The method of Aspect 63, wherein said additional component is an acid, cationic agent, caustic agent, chelating agent, color retention agent, coloring agent, dispersant, foaming agent, hydrolyzing agent, mercerization reagent, penetration enhancer, pH buffering agent, salt, solubilizing agent, stabilizing agent, surfactant, thickening agent, tracer, viscosity modifier, or wetting agent.

Aspect 65. The method of any one of the preceding Aspects, wherein the pretreating is performed using an anti-migrant, pH buffering agent, anionic agent, hydrolysis catalyst of alkali agent. Aspect 66. The method of any one of the preceding Aspects, wherein the pretreating is performed using a carboxylate salt, phosphate salt, sodium salt of polyacrylic acid, derivative of polyacrylate, copolymer of polyacrylate, polymaleic acid, sodium bicarbonate, sodium carbonate, sodium citrate, sodium citrate dibasic, tartrate salts, succinate salts, malonate salts, polymers comprising phosphate groups, or polymers comprising polyphosphate groups.

Aspect 67. The method of Aspect 66, wherein the carboxylate salt is sodium acetate, sodium stearate, or a salt of lactic acid.

Aspect 68. The method of Aspect 66, wherein the phosphate salt is sodium phosphate dibasic, sodium phosphate monobasic, or sodium pyrophosphate.

Aspect 69. The method of any one of the preceding Aspects, wherein the temperature is about 40 to about 80°C.

Aspect 70. The method of any one of the preceding Aspects, wherein the hydrolyzing is performed over about 5 seconds to about 5 minutes.

Aspect 71. The method of any one of the preceding Aspects, further comprising:

(iii) rinsing the substrate from step (ii).

Aspect 72. The method of Aspect 71, wherein rinsing is performed with an aqueous solution.

Aspect 73. The method of Aspect 72, wherein the aqueous solution further comprises an organic solvent, acid, cationic agent, caustic agent, chelating agent, color retention agent, coloring agent, dispersant, foaming agent, hydrolyzing agent, mercerization reagent, penetration enhancer, pH buffering agent, salt, solubilizing agent, surfactant, thickening agent, tracer, viscosity modifier, or wetting agent.

Aspect 74. The method of Aspect 72 or 73, wherein the aqueous solution further comprises a neutralization agent or buffering agent.

Aspect 75. The method of Aspect 72, wherein the pH of the dyed substrate is adjusted to about 5 to about 9.

Aspect 76. The method of any one of the preceding Aspects, wherein the substrate is a textile. Aspect 77. The method of any one of the preceding Aspects, wherein the substrate is a natural substrate such as a plant fiber such as cotton, kapok, hemp, bamboo, flax, sisal, jute, kenaf, ramie, bamboo, soybean, or coconut or an animal substrate such as silk, wool, leather, hair, or feather.

Aspect 78. The method of any one of Aspects 1-76, wherein the substrate is a synthetic substrate such as a polyamide such as nylon, polyester, acrylic, polyolefin, or spandex.

Aspect 79. The method of any one of the preceding Aspects, wherein the substrate is a yam.

Aspect 80. The method of any one of Aspects 1-78, wherein the substrate is a package of yam.

Aspect 81. The method of any one of Aspects 1-78, wherein the substrate is a fabric.

Aspect 82. The method of any one of the preceding Aspects, wherein the dyeing comprises dip dyeing, rope dyeing, slasher dyeing, spray dyeing, continuous dyeing, piece dyeing, space dyeing, package dyeing, skein dyeing, garment dyeing, paint bmsh dyeing, airbrush dyeing, blotch dyeing, foam dyeing, stamping, embossing, brushing, kiss rolling, screen printing, digital printing, doctor blading, knife rolling, kiss rolling, or coating.

Aspect 83. The method of any one of the preceding Aspects, wherein the dyeing is performed in the absence of a reducing agent to convert the compound to a leuco form of the compound.

Aspect 84. The method of Aspect 83, wherein the reducing agent is sodium hydrosulfite, formamidine sulfmic acid, glucose, sodium borohydride, sodium metabisulfite, thiourea dioxide, cellobiose, glyceraldehyde, fructose, or combinations thereof.

Aspect 85. A dyed substrate prepared according to any one of the preceding Aspects.

VII. Examples

[00182] All UV-Vis spectra were obtained using a Varian Cary 6000i UV-Vis

spectrophotometer.

[00183] Reactions of indigo with nicotinoyl chloride/isonicotinoyl chloride [00184] Example 1: Synthesis of Compounds 2 and 6

Compound 2: X = C, Y = N Compound 6: X = N, Y = C

[00185] To a suspension of indigo (54 g, 0.206 mol) in anhydrous pyridine (200 mL) in a 1.0L flask fited with a condenser and mechanical stirrer, under an inert atmosphere (Ar or N 2 ) was added isonicotinoyl chloride (92 g, 0.515 mol, 2.5 equivalents) portion wise with efficient stirring. The reaction mixture was heated to 50°C for 6 hours (the progress of the reaction was followed by TLC (5% MeOH in DCM, Rf 0.5). After this time, the deep red/pink reaction mixture was allowed to cool and most of the pyridine was removed under vacuum. The resulting reaction mixture was quenched by pouring into cold water (500 mL) with stirring for 30 minutes. The solid precipitate thus formed was isolated by filtration and washed thoroughly with cold water. The deep red solid was dried under vacuum and then dissolved in dichloromethane (1L); this solution was further dried using anhydrous sodium sulfate. The deep red solution was filtered and concentrated under vacuum until dry to afford a deep purple/red solid (60g, 61.8% yield). Characterization by 1 HNMR and MS confirmed the desired compounds.

[00186] Compound 2: Mw = C28H16N4O4, 472.45; ¾ NMR (400 MHz, DMSO) d 9.02 (s, 2H), 8.81 - 8.75 (m, 2H), 8.62 - 8.61 (m, 2H), 7.71 (d, J = 7.4 Hz, 1H), 7.69 - 7.63 (m, 1H), 7.61 (dd, J= 7.8, 4.9 Hz, 4H), 7.48 (dd, J= 9.3, 5.8 Hz, 2H), 7.28 (t, J= 7.8 Hz, 2H), 7.28 (t, J = 7.8 Hz, 2H).

[00187] Compound 6: Mw = C28H16N4O4, 472.45; ¾ NMR (400 MHz, DMSO) d 8.82 (d, J = 5.7 Hz, 4H), 7.80 (d, J = 18.1 Hz, 4H), 7.70 (d, J = 7.5 Hz, 2H), 7.65 (t, J = 7.6 Hz, 2H), 7.60 - 7.35 (m, 2H), 7.28 (t, J= 7.6 Hz, 2H). [00188] Example 2: Synthesis of Compound 28

[00189] To a suspension of indigo (5.2 g, 20 mmol) in anhydrous pyridine (50 mL) in a flask fited with a condenser and mechanical stirrer, under an inert atmosphere (Ar or N 2 ) was added 2-nicotinoyl chloride (14.2 g, 80 mmol, 4 equiv) portion wise with efficient stirring. The brown reaction mixture became quite thick and warm and was allowed to stir at room temperature for 30 mins and then gradually heated to 50°C hours (the progress of the reaction was followed by TLC (5% MeOH in DCM, Rf 0.3). The resulting reaction mixture was quenched by pouring into cold water (200 mL) with stirring for 30 minutes. The solid precipitate isolated by filtration proved to be un-reacted indigo. The aqueous was extracted into dichloromethane (3 x 50 mL), dried and concentrated to a give a brown solid which was purified using flash column chromatography. The main product isolated (stained yellow on TLC, Rf = 0.3 as above) as a yellow solid and was characterised by NMR. The analysis was not consistent with the above structure indicating that the 2-derivative behaves quite differently from the 3 and 4-derivatives when reacted with indigo.

[00190] ¾ NMR (400 MHz, DMSO) d 8.82 (d, = 4.7 Hz, 1H), 8.71 (d, .7= 4.1 Hz, 1H), 8.31

(t, J = 7.7 Hz, 1H), 8.09 - 7.95 (m, 1H), 7.88 - 7.79 (m, 1H), 7.68 - 7.59 (m, 1H), 7.47 - 7.39 (m, 1H), 7.36 (dd, .7= 6.5, 1.7 Hz, 1H), 6.32 (d, .7= 9.2 Hz, 1H), 6.19 - 6.14 (m, 1H).

[00191] Example 3: Synthesis of Compound 15

[00192] To a suspension of indigo (20 g, 0.076 mol) in anhydrous pyridine (100 mL) in a flask fited with a condenser and mechanical stirrer, under an inert atmosphere (Ar or N 2 ) was added isonicotinoyl chloride (l3g, 0.076mol, 1 equiv) portion wise with efficient stirring. The reaction mixture was heated to 50°C for 6 hours (the progress of the reaction was followed by TLC (5% MeOH in DCM, Rf 0.6; TLC also showed the presence of some di-substituted product). After this time, the deep red/pink reaction mixture was allowed to cool and most of the pyridine was removed under vacuum. The resulting reaction mixture was quenched by pouring into cold water (500ml) with stirring for 30 minutes. The solid precipitate thus formed was isolated by filtration and washed thoroughly with cold water. The deep red solid was dried under vacuum and then dissolved in dichloromethane (1L); this solution was further dried using anhydrous sodium sulphate. The deep red solution was filtered and concentrated under vacuum until dry to afford a deep purple/red solid. The crude material was separated by flash column chromatography (l%MeOH/dichloromethane). The pure product was separated as a bright pink solid in 25% yield (7 g).

[00193] Mw, C22H13N3O3, 367.36; ¾ NMR (400 MHz, DMSO) d 11.05 (s, 1H), 8.67 (d, J = 5.9 Hz, 2H), 7.88 (d, J= 7.5 Hz, 1H), 7.80 - 7.68 (m, 4H), 7.52 (t, J= 7.7 Hz, 1H), 7.39 (dd, J = 12.4, 7.2 Hz, 2H), 7.29 (d, .7= 8.1 Hz, 1H), 6.92 (t, J= 7.4 Hz, 1H).

[00194] Quatemization of nicotinoyl/isonicotinoyl derivatives

[00195] Example 4: Synthesis of Compounds 3 and 7

| p

[00196] To a refluxing solution of the precursor (Compound 2 or 6) in acetone, methyl iodide (3.2 equiv) was added drop-wise over 20 mins. The mixture was allowed to reflux for a further 5 hours and then allowed to cool to 0°C; the precipitated product was isolated by filtration and washed with ethyl acetate: pet ether (1: 1) and dried. The brown solid was isolated in quantitative yield.

[00197] Compound 3: Mw, 756.33, C30H22I2N4O4

[00198] Compound 7: Mw, 756.33, C30H22I2N4O4; ¾ NMR (400 MHz, DMSO) d 9.28 (d, J = 6.5 Hz, 4H), 8.50 - 8.38 (m, 4H), 8.14 (d, J = 8.2 Hz, 2H), 7.85 - 7.76 (m, 4H), 7.41 (t, J = 7.5 Hz, 2H).4.64 (s, 6H).

[00199] Example 5: Synthesis of Compound 16

[00200] To a refluxing solution of the precursor in acetone, methyl iodide (1.25 equiv) was added drop-wise over 20 mins. The mixture was allowed to reflux for a further 18 hours and then allowed to cool to 0°C; the precipitated product was isolated by filtration and washed with ethyl acetate: pet ether (1: 1) and dried.

[00201] Mw, 614.14, C29H19IN4O4

[00202] Example 6: Synthesis of Compound 18

[00203] Compound 6 (0.05 mol) was introduced into a pressure flask to which was added acetone (250 mL). The solution was saturated with chloromethane gas and sealed. The flask was heated to l00°C for 48 hours with stirring. After this time, the flask was allowed to cool to room temperature (TLC indicated complete consumption of the starting material). The product, which precipitated out, was isolated by filtration and washed with acetone and dried to constant weight. After drying, a purple solid was isolated which was characterized by 'H NMR (59% yield).

[00204] Mw 573.0, C30H22N4O4CI2; ¾ NMR (DMSO): d 9.2 (d, 4H, J= 6.5 Hz), 8.5 (d, 4H, J = 6.5 Hz), 8.1 (d, 2H, J= 8.2 Hz), 57.8 (m, 4H) 7.4 (d, 2H, J= 11 Hz), 4.4 (6H s).

[00205] Example 7: Synthesis of Compound 3B

[00206] Compound 2 (0.05 mol) is introduced into a pressure flask to which is added acetone (250 mL). The solution is saturated with chloromethane gas and sealed. The flask is heated to l00°C for 48 hours with stirring. After this time, the flask is allowed to cool to room temperature. The product, which precipitates out, is isolated by filtration and washed with acetone and dried to constant weight. After drying, a purple solid is isolated.

[00207] Example 8: Synthesis of Compounds 4, 8 and 41

[00208] Compound 2 or 6 was heated with anhydrous dialkylsulfate (R2SO4, R = Me, Et; 5 equiv) with stirring at 50°C for 18 hours under an inert atmosphere. TLC after this time showed the complete consumption of starting material. Once the reaction mixture was allowed to cool to room temperature, anhydrous diethyl ether (20 equiv) was added and the mixture stirred for 30 minutes. After this time, stirring was stopped and the precipitated compound was allowed to settle. The supernatant was removed via a filtered cannula under argon pressure. This process was repeated twice more to ensure removal of residual dimethyl sulfate. The solid residue was dried under a stream of Ar and stored under Ar, giving the product in almost quantitative yield

[00209] Compound 4 (J. Chem. Perk. Trans. 1984 2305-2309); Mw, 724.11, C32H28N4O12S2; ¾ NMR (400 MHz, CDCb) d 9.56 (s, 2H), 9.11 (d, 4H), 8.43 (dd, 2H), 8.0-7.4 (m, 8H).4.5l (s, 6H).

[00210] Compound 8: Mw, 724.11, C32H28N4O12S2; ¾ NMR (DMSO): d 9.2 (d, 4H, J = 6.6 Hz), 8.4 (d, 4H, J = 6.6 Hz), 8.1 (d, 2H, J = 7.4 Hz), 7.8 (t, 4H, J = 8.1 Hz), 7.4 (d, 2H, J = 7.4 Hz), 4.5 (s, 6H).

[00211] Compound 41: Mw, 724.11, C32H28N4O12S2; ¾ NMR (400 MHz, DMSO) d 9.35 (d, J= 10.0 Hz, 4H), 8.54 - 8.38 (m, 4H), 8.14 (d , J= 8.3 Hz, 2H), 7.78 (m, 6H), 7.48 - 7.34 (t, J = 12.1 Hz, 2H), 4.34 (q, J= 7.1 Hz, 4H), 3.74 (q, J= 7.1 Hz, 4H), 1.34 (t, J= 7.1 Hz, 6H), 1.1 it, J = 7.1 Hz, 6H).

[00212] Example 9: Synthesis of Compound 17

[00213] Compound 15 was heated with anhydrous dimethyl sulfate (5 equiv) with stirring at 50°C for 18 hours under an inert atmosphere. TLC after this time showed the complete consumption of starting material. Once the reaction mixture was allowed to cool to room temperature, anhydrous diethyl ether (20 equiv) was added and the mixture stirred for 30 minutes. After this time, stirring was stopped and the precipitated compound was allowed to settle. The supernatant was removed via a filtered cannula under argon pressure. This process was repeated twice more to ensure removal of residual dimethyl sulfate. The solid residue was dried under a stream of Ar and stored under Ar, giving the product in almost quantitative yield

[00214] Mw C24H19N3O7S, 493.43; ¾ NMR (400 MHz, DMSO) d 11.08 (s, 1H), 9.01 (d, J =

6.5 Hz, 2H), 8.51 (d, J = 6.5 Hz, 2H), 8.03 (d , J= 8.3 Hz, 1H), 7.93 (d, J= 7.5 Hz, 1H), 7.78 (t, J = 7.8 Hz, 1H), 7.53 (t, J = 7.5 Hz, 1H), 7.46 (d, J = 7.4 Hz, 1H), 7.41 (d, J = 7.5 Hz, 1H), 7.30 (d , J= 8.1 Hz, 1H), 6.94 (t, J= 7.4 Hz, 1H), 4.29 (s, 3H), 3.95 (s, 3H).

[00215] Protonation of nicotinoyl/isonicotinoyl derivatives

[00216] Example 10: Synthesis of Compound 35

[00217] Compound 6 (0.060 mol; as prepared above) was introduced into a flask to which was added dichloromethane (1L). A stream of hydrogen chloride gas was passed through the solution so formed at room temperature with occasional stirring. After a few minutes, the reaction mixture thickened and a precipitate formed. The mixture was allowed to stand under an atmosphere of HC1 gas for 1 hour. The solvent was removed under vacuum and the product was co-evaporated with anhydrous DCM (2 x 50 mL) and dried to constant weight to afford a purple solid, compound 35 (quantitative yield).

[00218] Mw, C28H18N4O12CI2, 545; ¾ NMR (400 MHz, DMSO) d 9.22 (bs, 4H), 8.28 (d, J = 5.3 Hz, 4H), 8.08 (bs, 2H), 7.82 - 7.68 (m, 4H), 7.35 (t, J= 12.7 Hz, 2H). [00219] Example 11: Synthesis of Compound 44

[00220] Compound 2 (0.060 mol; as prepared above) is introduced into a flask to which is added dichloromethane (1L). A stream of hydrogen chloride gas is passed through the solution at room temperature with occasional stirring. After a few minutes, the reaction mixture thickens and a precipitate forms. The mixture is allowed to stand under an atmosphere of HC1 gas for 1 hour. The solvent is removed under vacuum and the product is co-evaporated with anhydrous DCM (2 x 50 mL) and dries to constant weight.

[00221] Example 12: Synthesis of Compound 37

HSO 4 -

[00222] To a solution of compound 6 (5.0 g, l0.6mmol) in dichloromethane (30 mL) at 0°C under an atmosphere of argon was added a solution of anhydrous sulphuric acid (0.021 mol, 2.1 g) in methanol (25 mL) drop-wise with stirring over 30 mins. The mixture was allowed to stir at 0°C for a further 30 mins and then allowed to warm to room temperature. After 1 hour, anhydrous diethyl ether (100 mL) was added and the mixture stirred for 10 mins and then stirring was stopped and the precipitated solid was allowed to settle. The supernatant was removed by a filtered cannula under argon pressure; this process was repeated twice using 50 mL of diethyl ether each time. The product was isolated in quantitative yield as a bright red solid (7.0 g).

[00223] Mw C28H20N4O12S2, 668.47; mass analysis was consistent with the formation of the corresponding ion.

[00224] Compound 37 hydrolyzes to indigo under hydrolyzing conditions.

[00225] Reactions of indigo with alkoxy ethers

[00226] Example 13: Synthesis of Compound 13

[00227] Triphosgene (23.8 g, 80 mmol) was added to pyridine at 0°C and the mixture then allowed to warm to room temperature. After stirring for 30 mins at room temperature, indigo (10.5 g, 40 mmol) was added in one portion and the reaction allowed to stir overnight at room temperature. The mixture was then cooled in an ice bath and poured into ice cooled 4M HClaq with vigorous stirring and the precipitated solid was isolated by filtration. The solid was further washed with cold 4M HClaq followed by H2O. The solid was then dried under vacuum at 40°C to give a grey solid. This crude material was used for the following reactions.

[00228] Example 14: Synthesis of Compounds 14, 25, 29, 30, and 33

[00229] Compound 13 (3.0 g, 7.7 mmol) as prepared above) was suspended in the appropriate solvent (30 mL) and cooled in an ice-bath under an inert atmosphere. To this was added a THF solution of the alkoxy compound drop-wise (noted as "R" in Table 1) with stirring over 15 mins. The reaction mixture was allowed to stir at 0°C for 1 hour and then allowed to warm to room temperature over 18 hours (the progress of the reaction was followed by TLC 5% MeOH/DCM). The solvents were removed under vacuum followed by addition of diethyl ether (200ml) and stirred for 30 mins before decanting. The brown residue was taken up in DCM and purified using flash column chromatography. Fractions were characterized by 'H NMR.

Table 1

Compound R Solvent

[00230] Reactions of leuco-indigo

[00231] These reactions were carried out by generating leuco-indigo in-situ by oxidation of indigo by zinc and sodium acetate in the presence of acid chloride. [00232] Example 15: Synthesis of Compound 24B

[00233] To a suspension of indigo (1.31 g, 5 mmol) in anhydrous ethyl acetate (50 mL) containing sodium acetate (1.03 g, l2.5mmol) and zinc (3.25 g, 50 mmol) was added ethyl malonyl chloride (8.3 g, 50 mmol). The reaction mixture was allowed to stir for 30 mins at 40°C. The suspension was allowed to cool to room temperature and then concentrated to dryness. The residue was extracted with hot acetone. The crude material was purified using flash column chromatography eluting with 20% ethyl acetate: pet ether. The product was isolated as a pale yellow solid (0.5 g, 26%).

[00234] Mw = C21H18N2O5, 378.38; ¾ NMR (400 MHz, DMSO) d 12.17 (s, 1H), 11.90 (s, 1H), 8.27 (d, 7.5 Hz, 1H), 7.57 - 7.45 (m, 3H), 7.32 - 7.20 (m, 3H), 7.15 (ddd, J = 8.0, 7.0, 1.0 Hz, 1H), 4.05 (q, J= 7.1 Hz, 2H), 3.82 (s, 2H), 1.12 - 1.05 (t, 7.1 Hz, 3H).

[00235] Example 16: Synthesis of Compound 22

[00236] To a suspension of indigo (1.0 g, 3.8 mmol) in anhydrous ethyl acetate (50ml) containing sodium acetate (0.8 g, 9.5mmol) and zinc (2.49 g, 38 mmol) was added isonicotinoyl chloride (2.0 g, 11.4 mmol). The reaction mixture was allowed to stir for 30 mins at 40°C. The suspension was allowed to cool to room temperature and then concentrated to dryness. The residue was extracted with hot acetone. The crude material was purified using flash column chromatography eluting with 20% ethyl acetate: pet ether. The product was isolated as a pale yellow solid and was confirmed by 'H NMR to be the di-substituted product, Compound 22 (0.4g, 22%).

[00237] Mw, C28H18N4O4, 474.47; ¾ NMR (400 MHz, DMSO) d 11.36 (s, 1H), 11.12 (s, 1H), 7.59 (d, J= 8.0 Hz, 1H), 7.50 (dd, J = 8.1, 0.9 Hz, 1H), 7.46 - 7.41 (d, 8.1 Hz, 1H), 7.36 (d, J = 8.1 Hz, 1H), 7.16 (dddd, J= 12.9, 8.2, 7.0, 1.2 Hz, 2H), 7.05 (ddt, J= 8.1, 7.0, 1.1 Hz, 2H), 6.84 (dd, J= 2.1, 0.8 Hz, 1H). [00238] Example 17: Synthesis of Compound 20

[00239] Indigo (0.824 g, 3.1 mmol) was dissolved in pyridine and to this was added 3-benzoyl chloride sulfonyl chloride (3g, l2.4mmol). The mixture was heated to 50°C for 18 hours. After this time, the deep red mixture was poured onto cold water (100 ml) and stirred for 30 mins. The solid was isolated by filtration, dried under vacuum (l.98g, 69% yield) and characterised.

[00240] Example 18: Synthesis of Compound 27

[00241] Indigo (5.2 g, 20 mmol) was dissolved in pyridine and to this was added 3-sulphoyll chloride benzoic acid (17.4 g, 80 mmol). The mixture was heated to 50°C for 18 hours. After this time, the deep red mixture was poured onto cold water (lOOml) and stirred for 30 mins. The mixture was concentrated under vacuum to remove pyridine and the crude material was purified by column chromatography. The main fraction isolated by characterised by 'H NMR. Example 19: Synthesis of Compound 11

[00242] Indigo (2.62 g, 10 mmol) was added portion-wise to a suspension of N,N’- Disuccinimidyl carbonate (7.68 g, 30 mmol) in THF containing pyridine (0.125 mL) at 45°C with rapid stirring. The reaction mixture was allowed to stir at this temperature for 48 hours (the progress of the reaction was monitored by TLC, 5% MeOH/DCM). After this time, TLC showed a considerable amount of un-reacted indigo was still present; this was removed by filtration and the solid washed with DCM. The organic filtrate was concentrated to dryness and re-dissolved in DCM, washed with NaHCCb followed by H2O and then dried. Concentration under vacuum afforded a dark brown oil which was purified by column chromatography. [00243] Example 20: Synthesis of Compound 23

Compound 23

[00244] To a suspension of indigo (1.0 g, 3.8 mmol) in anhydrous ethyl acetate (50 mL) containing sodium acetate (0.8 g, 9.5 mmol) and zinc (2.49 g, 38 mmol) was added

chlorosulfonic acid (2.2 g, 19 mmol). The reaction mixture was allowed to stir for 30 mins at 40°C. The suspension was allowed to cool to room temperature and then filtered to remove zinc. The yellow brown filtrate was concentrated to dryness to give dark yellow oil.

[00245] Example 21: Synthesis of Compound 24A

[00246] To a suspension of indigo (1.31 g, 5 mmol) in anhydrous ethyl acetate (50 mL) containing sodium acetate (1.03 g, l2.5mmol) and zinc (3.25 g, 50 mmol) is added ethyl malonyl chloride (8.3 g, 50 mmol). The reaction mixture is allowed to stir at 40°C for at least 1 hour. The suspension is allowed to cool to room temperature and then concentrates to dryness. The residue is extracted with hot acetone. The crude material is purified using flash column chromatography eluting with 20% ethyl acetate: pet ether. [00247] Example 22: Synthesis of Compound 38

[00248] This compound is prepared using the procedure for Compound 18 in Example 6 using the corresponding free base.

[00249] Example 23: Synthesis of Compound 39

[00250] This compound is prepared using the procedure for Compound 37 in Example 12 using the corresponding free base.

[00251] Example 24: Synthesis of Compound 43

[00252] This compound is prepared by dissolving Compound 6 in DCM, followed by addition of chloroethane gas in dichloromethane/ethanol, dichloromethane/Bu4N + Br, ethanol, ethanol/pyridine, or isopropanol in a sealed pressure tube at lOO°C. The compound was then purified and isolated.

[00253] Example 25: Cotton Fabric Dyeing with Heat Treatment [00254] Prepared for dye (PFD) 3x1 twill cotton fabric dyed with Compound 8 was prepared by dipping in an aqueous solution containing 3 wt.% of Compound 8, padding, and drying at 50 °C. The samples were then placed separately into a lab-scale tenter frame for heat treatment. See, FIG. 1 showing the dyed fabric exposed to l00°C (left), l50°C (middle), and l80°C (right).

[00255] The images of FIG. 1 illustrate that the application of heat resulted in relatively rapid conversion of Compound 8 to indigo at l80°C, a slower conversion at l50°C, and no conversion at lOO°C.

[00256] Example 26: Cotton Fabric Dyeing with Heat Treatment and Pretreatment

[00257] Cotton skeins were pretreated with 1 M NaOH (aq), dyed with a 3 wt.% aqueous solution of Compound 8, hydrolyzed using 1 M NaOH (aq), and then rinsed with water. One skein was dried at 50°C and remained purple in color. See, the top skein in FIG. 2. The other skein was dried at 50°C and then exposed to steam under atmospheric conditions for 30 minutes, resulting in the attainment of a blue hue. See, the botton skein in FIG. 2.

[00258] The images of FIG. 2 illustrate that skeins can be dyed with Compound 8 followed by conversion to indigo using atmospheric steam.

[00259] Example 27

[00260] Image of -12 oz/square yard 3x1 twill fabrics that were prepared for dyeing, padded using a 6% aqueous solution of Compound 8, and dried at 60°C. The top row are the samples as they appeared following the 60°C drying step. The samples the bottom row were subjected to 10 minutes in a controlled temperature and humidity chamber (90°C, 90% humidity). The two samples on the left were not pretreated prior to padding the with dye. The middle two samples were padded using a 5% polyacrylic acid solution and dried at 80°C prior to padding with dye. The two samples on the right were padded using a 5% polyethyleneimine solution and dried at 80°C prior to padding with dye.

[00261] FIG. 3 shows incomplete conversion in the case of the polyethyleneimine pretreatment, partial conversion to indigo in the case of no pretreatment, and nearly complete-to- complete conversion to indigo in the case of polyacrylic acid pretreatment. In the case of digital printing of modified indigo onto polyacrylic acid-pretreated fabric, nearly complete-to-complete conversion to indigo following drying at 60°C in a convection oven.

[00262] Example 28 [00263] Digital printed fabrics using a 6% Compound 8 solvent-based ink. The ink was printed onto a polyacrylic acid-pretreated fabric and then dried at 60°C in a convection oven. Nearly complete conversion to indigo following drying was observed (sample on the left) upon drying at 60°C as was evident by the conversion from a red-magenta following printing to a blue color upon drying. A portion of the same sample was also treated following the drying step with a 1 M NaOH aqueous solution allowing for complete conversion to indigo (sample on the right). See, FIG. 4.

[00264] It is to be understood that while the invention has been described in conjunction with the preferred specific embodiments thereof, that the foregoing description and the examples that follow are intended to illustrate and not limit the scope of the invention. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention, and further that other aspects, advantages and modifications will be apparent to those skilled in the art to which the invention pertains. In addition to the embodiments described herein, the present invention contemplates and claims those inventions resulting from the combination of features of the invention cited herein and those of the cited prior art references which complement the features of the present invention. Similarly, it will be appreciated that any described material, feature, or article may be used in combination with any other material, feature, or article, and such combinations are considered within the scope of this invention.

[00265] The disclosures of each patent, patent application, and publication cited or described in this document are hereby incorporated herein by reference, each in its entirety, for all purposes.