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Title:
BENZO[1,2-B:4,5-B]FURAN DERIVATIVES AS LIGANDS OF RUTHENIUM DYES AND METHODS FOR OBTAINING THEREOF
Document Type and Number:
WIPO Patent Application WO/2016/111636
Kind Code:
A1
Abstract:
The present invention relates to a novel ligand for the synthesis of the photosensitizer ruthenium complexes for uses in DSSC, wherein said ligand comprise in their structure benzodifuran moiety bound directly or by a multiple bond with the 2,2'-bipyridine system in positions 4,4' or fluorene system and methods for preparing of said ligand. The subject of the invention is also a new symmetric or asymmetric photosensitizing ruthenium complex for use in DSSC derived from said ligand and methods for preparation of said complex. The resulting complexes have high molar extinction coefficients in the range of visible light and are stable in air environment and after exposure to sunlight, and may be used for the producing of Dye- Sensitized Solar Cells (DSSC). Developed methods are advantageous due to the mild reaction conditions, high repeatability and moderation or high yields.

Inventors:
BOSIAK, Mariusz, Jan (Broniewskiego 6/31, Toruń, PL-87-100, PL)
PAKULSKI, Marcin, Michał (Wspólna 2b/5 Przysiek, Zławieś Wielka, PL-87-134, PL)
WOLAN, Andrzej, Jan (Broniewskiego 4./15, Toruń, PL-87-100, PL)
RAKOWIECKI, Marcin (Mroza 22/8, Olsztyn, PL-10-692, PL)
Application Number:
PL2015/000206
Publication Date:
July 14, 2016
Filing Date:
December 23, 2015
Export Citation:
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Assignee:
SYNTHEX TECHNOLOGIES Sp. z o.o. (ul.Gagarina 7/134B, Toruń, PL-87-100, PL)
International Classes:
C07F15/00; C07D519/00
Foreign References:
US5463057A1995-10-31
Other References:
DATABASE CA [online] CHEMICAL ABSTRACTS SERVICE, COLUMBUS, OHIO, US; 2012, TANI, YUKIO ET AL: "Metal complex dye, photoelectric conversion element and photoelectrochemical cell", XP002755869, retrieved from STN Database accession no. 2012:195409
MARIUSZ J. BOSIAK ET AL: "Highly efficient benzodifuran based ruthenium sensitizers for thin-film dye-sensitized solar cells", DYES AND PIGMENTS., vol. 121, 19 March 2015 (2015-03-19), GB, pages 79 - 87, XP055260140, ISSN: 0143-7208, DOI: 10.1016/j.dyepig.2015.05.013
M.S. ZAKEERUDDIN; MK NAZEERUDDIN; M. GRAETZEL ET AL., LANGMUIR, vol. 18, 2002, pages 952
P. WANG; S.M. ZAKEERUDDIN; M.K. NAZEERUDDIN; M. GRÄTZEL ET AL., NAT. MATER, vol. 20, 2003, pages 402
P. WANG; C. KLEIN; R. HUMPHRY; BAKER, S.M. ZAKEERUDDIN; M. GRATZE, J. AM. CHEM. SOC., vol. 127, 2005, pages 808
M.K. NAZEERUDDIN; M. GRÄTZEL ET AL., JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A: CHEMISTRY, vol. 185, 2007, pages 331
J. PHYS. CHEM. C, vol. 113, 2009, pages 1998
C.Y. CHEN; S.J. WU; C.G. WU; J.G. CHEN; K.-C. HO, ANGEW. CHEM., vol. 118, 2006, pages 5954
P. GAO; M. GRATZEL ET AL., CHEM. COMMUN., 2008, pages 2635
J. AM. CHEM. SOC., vol. 130, 2008, pages 10720
C.Y. CHEN; M. GRATZEL ET AL., ACSNANO, vol. 3, 2009, pages 3103
Q. YU; P., WANG ET AL., J. PHYS. CHEM. C, vol. 113, 2009, pages 14559
Y. CAO; P. WANG ET AL., J. PHYS. CHEM. C., vol. 113, 2009, pages 6290
F. GAO; M. GRATZEL ET AL., J. AM. CHEM. SOC., vol. 130, 2008, pages 10720
Attorney, Agent or Firm:
KAMINSKI, Zbigniew (Kancelaria Patentowa, 02-011 Warszawa, PL-Al.Jerozolimskie 101/18, PL)
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Claims:
Claims

1. A ligand for synthesis of the photosensitizing ruthenium complexes use, wherein said ligand is at least one selected from the group comprising: compound of formula I

(Formula I)

wherein

Ri = H, alkyl, alkene, alkyne, aromatic hydrocarbon, polyglycol, organic salt, preferably tetrabutylammonium, and inorganic, preferably sodium; compound of formuia II

(Formula II)

wherein R-i = H, alkyl, alkene, alkyne, aromatic hydrocarbon, polyglycol, organic salt, preferably tetrabutylammonium, and inorganic, preferably sodium;

wherein Ri = H, alkyl, alkene, alkyne, aromatic hydrocarbon, polyg!ycol, organic salt preferably tetrabutytammonium, and inorganic, preferably sodium.

2. Symmetrica! or asymmetrical photosensitizing ruthenium complex for use in DSSC wherein said complex is selected from the group comprising:

complex of formula IV,

wherein Li = the ligand of formula I, L2 = a !igand of formula V;

complex of formula IV, wherein L| = L2 = ligand of formula I;

complex of formula IV, wherein L-i ~ ligand of formula II, L2 = ligand of formula

V;

complex of formula IV, wherein U = L2 = ligand of formula I I;

complex of formula IV, wherein L-j = ligand of formula III, L2 = ligand of formula V;

complex of formula IV, wherein Li = L2 = ligand of formula III.

3. A method for the preparing a ligand 6,6'-([2,2'-bipyridine]-4,4'-diyl)bis(2- methylbenzo[1 ,2-b: 4,5-j ']difuran-3-carboxylic acid) (1 ) of Formula I, as well as esters and salts thereof, wherein said method comprises the step of obtaining the ligand 1 by carrying out a Sonogashira reaction of 4,41-diha[ogeno-2,2'-bipyridine with ethynyltrimethylsilane in a solvent with a palladium catalyst, with or without addition of a phosphine, in the presence of copper halide and amine as a base, removing the trimethylsilyl groups from the intermediate product without isolation thereof by fluoride or alkaline hydrolysis in a mixture of water and alcohol or tetrahydrofuran, reacting 4,4-diethynyi-2 2'-bipyridine without isolation thereof with 5-hydroxy-6-haio-2-methyt- benzofuran-3-carboxylate at room or higher temperature to yield the ligand of formula I, and if necessary, hydrolyzing said ligand under basic or acidic conditions and isolating the product.

4. The method according to claim 3, wherein the solvent is selected from aliphatic, cycloaiiphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, ketone, ester or lactone, N-substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably the solvent is selected from toluene, xylene, tetrahydrofuran, dimethyl sulfoxide, acetonitrile nad 1 ,4-dioxane.

5. The method according to claim 3, wherein the catalyst is a palladium compound selected from the group consisting of palladium(!l) dihalides, pa!ladium(li) acetate, palladium(ll) sulfate, bis(triphenylphosphine)palIadium(ll) dichloride, bis(tricyclopentylphosphine) palladium(ll) dichloride, bis(tricyciohexylphosphine) paliadium(ll), bis(dibenzylideneacetone)palladium(0), tetrakis (triphenylphosphine) pailadium(O), preferably [1 ,1'-bis(diphenylphosphino)ferrocene]dichioropalladium(ll).

6. The method according to claim 3, wherein the reaction is carried out with or without addition of an aromatic or nonaromatic phosphine.

7. The method according to claim 3, wherein the reaction is carried out with the addition of a copper halide, preferably copper iodide.

8. A method according to claim 3, wherein the reaction is carried out in the presence of aliphatic, alicyclic, aromatic, heterocyclic amine, preferably diisopropylamine, at room temperature or higher temperature.

9. The method according to claim 3, wherein the trimethylsilyl groups in the intermediate product are removed without isolation thereof using organic or inorganic fluorides or alkaline hydrolysis in a mixture of water and alcohol or tetrahydrofuran, preferaiby the trimethylsily! groups in the intermediate product are removed with tetrabutyiammonium fluoride.

10. The method according to claim 3, wherein the obtained 4,4-diethynyi-2,2'- bipyridine, without isolation thereof, is reacted with an ester of 5-hydroxy-6-halo-2- methyl-benzofuran-3-carboxylic acid in the same flask, preferably the obtained 4,4- diethynyl-2,2'-bipyridine is reacted with an ester of 5-hydroxy-6-0romo-2-methyl- benzofuran-3-carboxylic acid or 5-hydroxy-6-iodo-2-methy!-benzofuran-3-carboxylic acid, especially with an ester of 5-hydroxy-6-iodo-2-methyl-benzofuran-3-carboxy[ic acid.

11. The method according to claim 3, wherein the reaction of 4,4'-diethynyi- 2,2'-bipyridine with ester of 5-hydroxy-6-iodo-2-methyl-benzofuran-3-carboxylic acid is carried out at room temperature or higher temperature, preferably at a temperature of 80°C.

12. A method for the preparing a ligand 6,6'-((1 ,1 'H3,3'-b!pyridine]-4,4'- diylbis(eteno-2,1-diyl))bis(2-methylbenzo[1 ,2-6:4, 5-6']difuran-3,7-dicarboxylic) acid (2) of Formula II, and esters and salts thereof, wherein the method comprises step of carrying out the Wittig reaction of [2,2'-bipyridine]-4,4'-dikarboaldehyde with ((3,7- bisfalkoxycarbonylJ-e-methylbenzotl ^-jb^.S-bldifuran^-ylJmethy tritriphenyl- phosphonium haiide in an organic solvent in the presence of a base at room or higher temperature to yield the ligand of formula i, and if necessary, hydrolyzing said ligand under basic or acidic conditions and isolating the product.

13. The method according to claim 12, wherein the solvent is selected from the group of an alcohol, hydrocarbon, aliphatic, cycloaliphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, ketone, ester or lactone, N- substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably isopropanol.

14. The method according to claim 12, wherein the base is alkali metal hydroxide or mixture thereof, preferably lithium hydroxide or a hydrate thereof.

15. The method according to claim 12, wherein the reaction is carried out at room temperature or higher temperature, preferably at the reflux temperature of isopropanol.

16. A method for the preparing a ligand 2-((5/-/-cyclopenta[1 , 2-0:5,4- ^dipirydyn-S-ylideneJmethylJ-B-methylbenzofl ,2-i>:4,5-£>']difuran-3,7-dicarboxylic acid (3) represented by formula Hi and esters and salts thereof, wherein said method comprises carrying out the Wittig reaction of 5/-/-cyc!openta[1 ,2-£>: 5,4-i>1dipyridin-5- one with ((3,7-bis(alkoxycarbonyl)-6-methylbenzo[ ,2-6:4,5-01difuran-2-yl)methyl) tritriphenyiphosphonium halide in a solvent, in the presence of a base at room or higher temperature to yield the ligand of formula i, and if necessary, hydrolyzing said iigand under basic or acidic conditions and isolating the product.

17. The method according to claim 16, wherein the solvent is selected from the group of an alcohol, hydrocarbon, aliphatic, cycloaiiphatic or aromatic hydrocarbon, aiiphatic halohydrocarbon, nitrile, ether, ketone, ester or lactone, N- substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably isopropanoi.

18. The method according to claim 16, wherein the base is alkali metai hydroxide or mixture thereof, preferably used lithium hydroxide or a hydrate thereof.

9. The method according to claim 16, wherein the reaction is carried out at room temperature or higher temperature, preferably at the reflux temperature of isopropanoi.

20. A method for the preparing of c/s-bis{isothiocyanate)(6,6'-([2,2'- bipyridine]-4,4'-diyl)b!s(2-methylbenzo[1 ,2-i):4,5-0']difuran-3-karboksylo))(2,2'- bipyridyl-4,4'-dikarboksylo)ruthenium(II) complex (4) of formula IV, wherein L-i = the ligand of formula I, L2 = a ligand of formula V, and esters and salts thereof, wherein the method for obtaining of complex 4 comprises reacting ruthenium(ll!) chloride or dimer of dichloro(p-cymeno)ruthenium(ll) with ligand 1 , 2,2'-bipyridine-4,4'- dicarboxylic acid and inorganic thiocyanate in a solvent and isolating the product.

21 . The method according to claim 20, wherein the source of ruthenium is preferably a dimer of dichloro(p-cymene)ruthenium(ll).

22. The method according to claim 20, wherein the solvent is selected from the group of alcohol, hydrocarbon, aliphatic, cycloaiiphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, ketone, ester or lactone, N-substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably W,W-dimethylformamide.

23. The method according to claim 20, wherein the complex 4 is obtained in one process, without isolation of intermediates.

24. The method according to claim 20, wherein the reaction is carried out at room temperature or higher temperature, preferably at a temperature of 140-150°C.

25. A method for the preparing of c/s-bisiisothiocyanatejbisfe.e'-ip^'" bipyhdine]-4,4'-diyl)bis(2-methylbenzo[1 ,2-0:4,5-jb']difuran-3-karboksylo))ruthenium(il) complex (5) the formula IV, wherein l_i = L2 = a Iigand of formula i, as well as esters and salts thereof, wherein the method for obtaining the complex 5 comprises reacting ruthenium chloride (111) or dimer dichloro(p-cymene)ruthenium(ll) with Iigand 1 and inorganic thiocyanate in a solvent and isolating the product.

26. The method according to claim 25, wherein the source of ruthenium is preferably a dimer dichloro(p-cymene)ruthenium(ll).

27. The method according to claim 25, wherein the solvent is selected from the group of an alcohol, hydrocarbon, aliphatic, cycloaliphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, ketone, ester or lactone, N- substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably A/,A/-dimethylformamide.

28. The method according to claim 25, wherein the complex 5 is obtained in one process, without isolation of intermediates.

29. The method according to claim 25, wherein the reaction is carried out at room temperature or higher temperature, preferably at a temperature of 140-150°C.

30. A method for the preparing of c/s-bis{isothiocyanate)(6,6'-((1 ,1 ')-[3,3'- bipyridine]-4,4,-diylbis(eteno-2,1 -diyl))bis(2-methylbenzo[1 ,2-b:4,5-ji)']difuran-3,7- dikarboksyio))(2,2'-bipyridyl-4,4'-dikarboksylo)ruthenium(!l) complex (6) of formula IV, wherein l_i = Iigand of formula II, L2 = Iigand of formula V, and esters and salts thereof, wherein the method for obtaining a complex 6 comprises reacting ruthenium(lll) chloride or dichloro(p-cymeno)ruthenium(ll) dimer with Iigand 2, 2,2'- bipyridine-4,4'-dicarboxylic acid and inorganic thiocyanate in a solvent and isolating the product.

31. The method according to claim 30, wherein the source of ruthenium is preferably dichloro(p-cymene)ruthenium(ll) dimer.

32. The method according to claim 30, wherein the solvent is selected from the group of an alcohol, hydrocarbon, aliphatic, cycloaliphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, ketone, ester or lactone, N- substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably Λ/,Ν-dimethylformamide.

33. The method according to claim 30, wherein the complex 6 is prepared in one method without isolation of intermediates.

34. The method according to claim 30, wherein the reaction is carried out at room temperature or higher temperature, preferably at a temperature of 140-150°C.

35. A method for the preparing of c/s-bisiisothiocyanateJbisiG.G'-ifl ')-^^'- bipyridine]-4,4,-diylbis(eteno-2,1 -diyl))bis(2-methylbenzo[1 ,2-i):4,5- ),]difuran-3,7- dikarboksy!o)ruthenium(ll) complex (7), of formula IV, wherein l_i = l_2 = ligand of formula II and esters and salts thereof, wherein the complex 7 is obtained by reacting ruthenium chloride (111) or dichloro(p-cymene)ruthenium (II) dimer with ligand 2, and inorganic thiocyanate in a solvent and isolating the product.

36. The method according to claim 35, wherein the source of ruthenium is preferably dichloro(p-cymene)ruthenium(ll) dimer.

37. The method according to claim 35, wherein the solvent is selected from the group of an alcohol, hydrocarbon, aliphatic, cycloaliphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, ketone, ester or lactone, N- substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably W,/V-dimethylformamide.

38. The method according to claim 35, wherein the complex 7 is obtained in one process, without isolation of intermediates.

39. The method according to claim 35, wherein the reaction is carried out at room temperature or higher temperature, preferably at a temperature of 140-150°C.

40. A method for the preparing of c/s-bis(isothiocyanate)(2-((5H- cyclopentatl ^-b!S^-^Jdipirydyn-S-ylideneimethylJ-e-methy!benzon ^-/)^^- £)']difuran-3,7-dikarboksy!o){2,2'-bipyridyl-4,4'-dikarboksylo)ruthenium(ll) complex (8), of formula IV, wherein l_i = ligand of formula Ml, L2 = ligand of formula V; and esters and salts thereof, wherein the method for obtaining complex 8 comrpises reacting ruthenium chloride (III) or dichloro(p-cymene)ruthentum (li) dimer with ligand 3, 2,2'- bipyridine-4,4'-dicarboxylic acid and an inorganic thiocyanate in a solvent and isolating the product.

41. The method according to claim 40, wherein the source of ruthenium is preferably dichloro(p-cymene)ruthenium(ll) dimer.

42. The method according to claim 40, wherein the solvent is selected from the group of an alcohol, hydrocarbon, aliphatic, cycloaliphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, ketone, ester or lactone, N- substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably A/./ -dimethylformamide.

43. The method according to claim 40, wherein complex 8 is obtainable in one process, without isolation of intermediates.

44. The method according to claim 40, wherein the reaction is carried out at room temperature or higher temperature, preferably at a temperature of 140-150°C.

45. A method for the preparing of c s-bis(isothiocyanate)bis(2-((5H- cyc!openta[1 , 2-0:5, 4-/)'3dipirydyn-5-ylidene)methyl)-6-methylbenzo[1 , 2-^:4,5- 0']difuran-3,7-dikarboksylo)ruthenium(ll) complex (9) of formula IV, wherein Li = L2 = ligand of formula 111, wherein the method for obtaining complex 9 comprises reacting ruthenium chloride (111) or dimer dichloro(p-cymene)ruthenium (II) ligand 3 and thiocyanate inorganic solvent and isolating the product.

46. The method according to claim 45, wherein the source of ruthenium is preferably dichloro(p-cymene)ruthenium(ll) dimer.

47. The method according to claim 45, wherein the solvent is selected from the group of an alcohol, hydrocarbon, aliphatic, cycloaliphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, ketone, ester or lactone, N- substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably W,A/-dimethyIfarmamide.

48. The method according to claim 45, wherein the complex 9 is obtained in one process, without isolation of intermediates.

49. The method according to claim 45, wherein the reaction is carried out at room temperature or higher temperature, preferably at a temperature of 140- 50°C.

Description:
Benzofl derivatives as iigands of ruthenium dyes and methods for obtaining thereof

The present invention relates to the Iigands comprising in their structure benzodifuran moiet and ruthenium complexes constructed on the basis on said Iigands and methods for their preparing, and use for DSSC thereof.

M. Gretzel and M.K. Nazeeruddin in US005463057A disclose a complex of two molecules of 2,2'-bipyridyl-4,4'-dicarboxylic acid (dcbpy) with ruthenium and isothiocyanate groups, having been converted into a tetrabutylammonium salt, for the purpose of improving the solubility in alcohols, water and the polar organic solvents, said complex is used as a photosensitizer of titanium oxide in the dye photovoltaic cells of DSSC type.

The mixed ruthenium complexes which comprise two different Iigands comp!exed to the ruthenium atom are also known. M.S. Zakeeruddin, MK Nazeeruddin, M. Graetzel et a!. in Langmuir 2002, 18, 952, described mixed dyes formed from a single dcbpy molecule and single molecule of 4,4'-ditridecyl-2,2'- bipyridine, 4-methyl-4'~hexadecyl-2,2'-bipyridine or 4-methyl-4 , -(2-dodecyltetradecyl)- 2,2'-bipyridine. These dyes have shown IPCE (incident photon-to-current conversion efficiency) of 80% and high desorption stability from the surface of titanium oxide caused by water, so that they can be used in combination with a water-based electrolytes.

P. Wang, S.M. Zakeeruddin, M.K. Nazeeruddin, M. Gratzei, et ai. in Nat. Mater. 2003, 20, 402, describe amphiphilic dye Z907 comprising one dcbpy ligand and one 4,4'-dinonyl-2,2'-bipyridine ligand having similar effect. Then, P. Wang, C. Klein, R. Humphry-Baker, S.M. Zakeeruddin, and M. Gratzei, in J. Am. Chem. Soc. 2005, 127, 808, describe heteroleptic ruthenium complex, designed with symbol K-19, comprising in addition to dcbpy an aryl-viny! ligand 4,4'-bis((E)-4-(hexyloxy)styryl)- 2,2'-bipyridine, which due to the extended system of coupled π bonds show increased absorption of visible light compared to those known in the state of the art.

M.K. Nazeeruddin, M. Gratzei et al. in Journal of Photochemistry and Photobiology A: Chemistry 2007, 185, 331 also presented similar complexes, called N945, and K9 and K23, described in J. Phys. Chem. C, 2009, 113:1998, which show a much higher molar extinction coefficient compared to complexes without a conjugated bond system in one of the ligands as well as a shorter lifetime of electrons and rapid recombination.

C.Y. Chen, S.J. Wu, C.G. Wu, J.G. Chen and K.-C. Ho in Angew. Chem. 2006, 118, 5954, describe a ruthenium complex CYC-B1 , consisting of a single dcbpy iigand and single ligand 4,4'-bis(5'-octyl-[2,2'-bithiophene3-5-yl)-2,2'-bipyridine. Due to the aromatic conjugated system containing an aikyl-bithiophen group, similarly as described above aryl-vinyl systems, this ligand makes the ruthenium complex to be characterized by the high value of the molar extinction coefficient. Moreover incorporation of the thiophene system to the bipyridyl ligand may increase energy levels of metal center and LU O orbital of the ligand. Consequently, the absorption band derived from the passage of the "charge transfer" type from metal to ligand shifts toward longer wavelengths.

Similar complexes comprising thiophene derivatives were described by P. Gao, M. Gratzel et al. (Chem. Commun., 2008, 2635 and J. Am. Chem. Soc. 2008, 130, 10720), C.Y. Chen, M. Gratzel et al. (AcsNano, 2009, 3, 3103), Q. Yu, P., Wang et al. (J. Phys. Chem. C 2009, 1 13, 14559), Y. Cao, P. Wang et al. (J. Phys. Chem. C. 2009, 1 13, 6290).

F. Gao, M. Gratzel et al., in J. Am. Chem. Soc. 2008, 130, 10720 describe, in addition to the thiophene derivative, also furan derivatives. The state of the art does not, however, comprise any teaching on ligands substituted in positions 4,4' of the 2,2'-bipyridine with benzodifuran and benzofuran groups which show absorption of UV-Vis radiation with high molar extinction coefficients.

The subject of the present invention are novel ligands for the synthesis of the photosensitizing complexes of ruthenium for use in DSSC

wherein said ligand has formula I, wherein Ri = H, alkyl, alkene, aikyne, aromatic hydrocarbon, polyglycol, organic salt (eg. tetra-butylammonium) and inorganic salt (e.g. sodium);

formula II, wherein Ri = H, alkyl, alkene, aikyne, aromatic hydrocarbon, polyglycol, organic salt (e.g. tetrabutylammonium) and inorganic salt (e.g. sodium);

Formula ! Formula l!l

The subject of the invention are further new symmetric and asymmetric photosensitizing ruthenium complexes of the invention for use DSSC wherein

the complex has formula IV, wherein U = ligand of formula I, L 2 = !igand of formula V;

formula IV, wherein Li = L 2 = ligand of formula I;

formula IV, wherein U = ligand of formula II, L 2 = ligand of formula V;

formula IV, wherein U = L 2 = ligand of formula II;

formula IV, wherein U = ligand of formula III, L 2 = ligand of formula V;

formula IV, wherein L-i = L 2 = ligand of formula III.

Formula V

The subject of the invention is a method for the preparing a 6,6'-([2,2'- bipyridine]-4,4'-diyl)bis(2-methylbenzo[1 ,2-6:4, 5-6']difuran-3-carboxylic) acid ligand (1) of formula ! according to the invention, esters and salts thereof, wherein said method comprises the steps of obtaining ligand 1 using the Sonogashira reaction of 4,4'-dihalo-2,2'-bipyridine with ethynyltrimethylsilane in a solvent, in the presence of a palladium catalyst, with or without addition of a phosphine, in the presence of copper halide and amine as a base; wherein removing the trimethylsilyl groups in the intermediate product is carried out without isolation thereof, with the use of fluoride or alkaline hydrolysis in a mixture of water and alcohol or tetrahydrofuran, reacting resulted 4,4-diethynyl-2,2'-bipyridine without isolation thereof with an ester of 5- hydroxy-6-haIo-2-methyibenzofuran-3-carboxylic acid at room temperature or higher temperature to yield the Iigand of formula I, hydrolyzing thereof, if necessary, under basic or acid conditions and isolating using a known method.

Suitable solvents are aliphatic, cycloaliphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrite, ether, alcohol, ketone, ester or lactone, N- substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents. Preferably the solvent is selected from toluene, xylene, tetrahydrofuran, dimethyl sulfoxide, acetonitrile or 1 ,4-dioxane or mixture thereof.

The catalyst used according to the invention is a palladium compound selected from the group consisting of paliadium(!l) dihalides, palladium(ll) acetate, palladium(il) sulfate, bis(triphenylphosphine)paliadium(l[) dichloride, bis(tricyclopentyIphosphine)palladium(ll) dichloride, bis(tricyclohexylphosphine)- palladium(ll), bis(dibenzylideneacetone)palladium(0), tetrakis(triphenylphosphine)palladium(0), preferably [1 ,1'-bis (dipheny!phosphino) ferrocene]dichloropalladium(ll).

The reaction is carried out with or without addition of aromatic or nonaromatic phosphine.

The reaction is carried out with the addition of a copper halide, preferably copper iodide.

The reaction is carried out in the presence of aliphatic, alicyclic, aromatic, heterocyclic amine, preferably diisopropylamine, at room temperature or higher temperature.

The method comprises the step of removing the trimethy!silyl groups from the intermediate without isolation thereof using organic or inorganic fluorides, or alkaline hydrolysis in a mixture of water and alcohol or tetrahydrofuran, preferably tetrabutylammonium fluoride.

Preferably, the method comprise step of reacting in the same flask resulting 4,4'-diethynyl-2,2'-bipyridine, without isolation thereof, with an ester of 5-hydroxy-6- halo-2-methyl-benzofuran-3-carboxylic acid. More preferably, reacting the resulting 4 J 4'-diethynyl-2,2'-bipyridine with 5- hydroxy-6-bromo-2-methyl-benzofuran-3-carboxylic acid ester or 5-hydroxy-6-iodo-2- methyi-benzofuran-3-carboxylic acid ester.

Most preferably, the resulting 4,4'-diethynyl-2,2'-bipyrid!ne is reacted with 5- hydroxy-6-iodo-2-methyl-benzofuran-3-carboxyiic acid ester.

The reaction of 4,4'-diethinylo-2,2 , -bipyridine with 5-hydroxy-6-iodo-2-methyl- benzofuran-3-carboxylic acid ester is carried out at room temperature or higher temperature, preferably at 80°C.

The subject of the invention is also a method for the preparing 6,6'-((1 ,1')- [3,3 , -bipyridine]-4,4'-diyibis(etheno-2,1-diyl))bis(2-methy lobenzo[1 ,2-b:4,5-^']-difuran- 3,7-dicarboxylic) acid ligand (2) of Formula II, according to the invention, and esters and salts thereof, wherein the method comprises the steps of obtaining the ligand 2 using the Wittig reaction of [2,2'-bipyridine]-4,4'-carbaldehyde with ((3,7- bis(alkoxycarbonyl)-6-methylbenzo[1 ,2-/):4,5-iti]difuran-2-yl)methyl)triphenyi- phosphonium halide in an organic solvent in the presence of a base, at room temperature or higher temperature, if necessary, hydrolyzing thereof under basic or acidic conditions and isolating using a known method.

The suitable solvents are alcohol, hydrocarbon, aliphatic, cycloaiiphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, ketone, ester or lactone, N-substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably isopropanol.

The sutiabte base are hydroxides of alkali metals, preferably lithium hydroxide or a hydrate thereof.

The reaction is carried out at room or elevated temperature, preferably at the reflux temperature of isopropanol.

The further subject of the invention is a method for the preparing 2-((5H- cyclopenta[1 ,2-0:5, 4-0']dipyridin-5-ylidene)methyl)-6-methylbenzo[1 ,2-jb:4,5-b']difuran- 3,7-dicarboxy!ic acid ligand (3) of the formula III according to the invention and esters and salts thereof, wherein the method comprises the steps for obtaining a ligand 3 using the Wittig reaction of 5H-cyclopenta[1 ,2-j :5,4-j ]dipyridin-5-one with ((3,7- bis(alkoxycarbonyl)-6-methylbenzo[1 ,2-0:4,5-/ ']difuran-2-yl)methyl)

tritriphenylphosphonium halide in a solvent, in the presence of a base, at room temperature or higher temperatureand which, if necessary, hydrolyzing thereof under basic or acidic conditions and isolating using a known method.

The suitable solvent is an alcohol, hydrocarbon, aliphatic, cycloaliphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, ketone, ester or lactone, N-substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably isopropanol.

The suitable base is one of the hydroxides of alkali metals, preferably lithium hydroxide or a hydrate thereof.

The reaction is carried out at room or elevated temperature, preferably at the reflux temperature of isopropanol.

The still further subject of the invention is method for the preparing of c/ ' s- bis(isothiocyanate)(6,6'-([2,2'-bipyridine]-4,4'-diyI)bis(2- methylbenzo[1 ,2-0:4,5- £) , ]difuran-3-karboksyio)){2,2'-bipyridyl-4,4'-dikarboksy lo)ruthenium([l) complex (4) of formula IV, wherein l_i = ligand of formula I, L2 = ligand of formula V, according to the invention, and esters and salts thereof, wherein method for obtaining the complex 4 comprises step of reacting ruthenium(HI) chloride or a dimer of dichloro(p- cymene)ruthenium(ll) with ligand 1 , 2,2'-bipyridine-4,4'-dicarboxylic acid and inorganic thiocyanate in a solvent and isolating the product using a known manner.

Preferably, the source of ruthenium is a dimer of dichloro(p-cymene)- ruthenium(ll).

The suitable solvent is an alcohol, hydrocarbon, aliphatic, cycloaliphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, ketone, ester or lactone, N-substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably N,N-dimethylformamide.

The complex 4 is obtained in one process, without isolation of intermediates.

The reaction is carried out at room or elevated temperature, preferably at a temperature of 140-150°C.

The further subject of the invention is a method for the preparing of c/s- bis{isothiocyanate)bis(6,6'-([2,2 , -bipyridine]-4,4 , -diyl)bis(2-methylbenzo[1 , 2-0:4,5- jb']difuran-3-karboksylo))ruthenium(ll) complex (5) having the formula IV, wherein l_i = L 2 = ligand of formula I according to the invention and esters and salts thereof, wherein the method comprises the step of obtaining the complex 5 by reacting ruthenium(lll) chloride or a dimer of dichloro(p-cymene) ruthenium(il) with Sigand 1 and inorganic thiocyanate in a solvent and isolating the product using a known manner.

Preferably, the source of ruthenium is a dimer of dichloro(p-cymene) ruthenium(l!).

The suitable solvent is an alcohol, hydrocarbon, aliphatic, cycloaliphatic or aromatic hydrocarbon, aliphatic haiohydrocarbon, nitrile, ether, ketone, ester or lactone, N-substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably N,N-dimethylformamide.

The complex 5 is obtained in one process, without isolation of intermediates.

The reaction is carried out at room or elevated temperature, preferably at a temperature of 140-150°C.

The still further subject of the invention is a method for the preparing of c/s- bis(isothiocyanate)(6 I 6'-((1 ,1 [3,3'-bipy dine]-4,4 , -diylbis(eteno-2, 1-diyl))bis(2- methylbenzo[1 ,2-6:4,5-0 , ]difuran-3,7-dikarboksylo))(2,2'-bipyridyl-4,4'- dikarboksylo)ruthenium(il) complex (6) of formula IV, wherein l_i = ligand of formula II, l_2 = ligand of formula V, according to the invention, and esters and salts thereof, wherein the method for obtaining complex 6 comprises the step of reacting ruthenium(!ll) chloride or dimer of dichloro(p-cymene)ruthenium(ll) with ligand 2, 2,2 - bipyridine-4,4'-dicarboxylic acid and inorganic thiocyanate in a solvent and isolating the product using a known manner.

Preferably, the source of ruthenium is a dimer of dichloro(p-cymene)- ruthenium(ll).

The suitable solvent is an alcohol, hydrocarbon, aliphatic, cycloaliphatic or aromatic hydrocarbon, aliphatic haiohydrocarbon, nitrile, ether, ketone, ester or lactone, N-substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably N,N-dimethylformamide.

The complex 6 is obtained in one process, without isolation of intermediates.

The reaction is carried out at room or elevated temperature, preferably at a temperature of 140-150°C.

The further subject of the invention is a method for the preparing of cis- bis(isothiocyanate)bis(6,6 (1 ,1 [3,3'-bip^^^ methylbenzo[1 ,2-jb:4,5-^difuran-3 ( 7-dikarboksylo)ruthenium(ll) complex (7) of formula IV, wherein l_i = L 2 = ligand of formula II according to the invention, and esters and salts thereof, wherein method for obtaining the complex 7 comprises the step of reacting ruthenium(III) chloride or dimer of dichloro{p-cymene)ruthenium (II) with ligand 2, and inorganic thiocyanate in a solvent, and isolating the product using a known manner.

Preferably, the source of ruthenium is a dimer of dichloro(p-cymene)- ruthenium (II).

The suitable solvent is an alcohol, hydrocarbon, aliphatic, cycloaliphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, ketone, ester or lactone, N-substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably the suitable solvent is W,N-dimethylformamide.

The complex 7 is obtained in one process, without isolation of intermediates.

The reaction is carried out at room or elevated temperature, preferably at a temperature of 140-150°C.

The further subject of the invention is a method for the preparing of cis- bis(isothiocyanate)(2-((5H-cyclopenta[1 ^-/jiS^-^Jdipirydyn-S-ylideneJmethylJ-e- methy!benzo[1 ,2-£):4,5-i) , ]difuran-3,7-dikarboksylo)(2,2'-bipyridyl-4,4'- dikarboksylo)ruthenium(ll) complex (8), of formula IV, wherein l_i = the ligand of formula III, L 2 - a ligand of formula V; according to the invention, and esters and salts thereof, wherein the method for obtaining complex 8 comprises the step of reacting ruthenium chloride(ll l) or dimer dichloro{p-cymene)ruthenium(ll) with ligand 3 2,2'- bipyridine-4,4'-dicarboxylic and inorganic thiocyanate in a solvent and isolating the product using a known manner.

Preferably, the source of ruthenium is a dimer of dichloro(p-cymene)- ruthenium(ll).

The suitable solvent is an alcohol, hydrocarbon, aliphatic, cycloaliphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, ketone, ester or lactone, N-substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably Ν,Ν-dimethylformamide.

The complex 8 can be obtained in one process, without isolation of

intermediates. The reaction is carried out at room or elevated temperature, preferably at a temperature of 140-150°C.

The further subject of the invention is a method for the preparing of c/s- bis(isothiocyanate)bis(2-({5H-cycIopenta[1 ^-jbiS^-b'Jdipirydyn-S-yiideneJmethylJ-e- methylbenzo[1 ,2-jf}:4,5-i ']difuran-3,7-dikarboksylo)ruthenium(ll) complex (9), of formula IV, wherein l_i = L 2 = ligand of formula III, according to the invention, and esters and salts thereof, in which complex 9 is obtained by reacting ruthenium(lll) chloride or dimer dichloro(p-cymene)ruthenium(ll) ligand 3 and inorganic thiocyanate in a solvent and isolating the product using a known manner.

Preferably, the source of ruthenium is a dimer of dichloro(p-cymene)- ruthenium(ll).

The suitable solvent is an alcohol, hydrocarbon, aliphatic, cycloaliphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, ketone, ester or lactone, N-substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably A/,/V-dimethylformamide.

The complex 9 is obtained in one process, without isolation of intermediates.

The reaction is carried out at room or elevated temperature, preferably at a temperature of 140- 50°C.

Description of the Invention

Developed symmetric and asymmetric ruthenium complexes 3-9 show the absorption of visible light and UV with high molar extinction coefficients and can be used as dye for the production of DSSC (Dye-Sensitized Solar Cells). The products are stable in air and after exposure to sunlight.

Developed procedures are characterized by mild reaction conditions, high repeatability and performance of the resulting products is moderate or high.

The precursors for the synthesis of ligand 1 are the esters of 5-hydroxy-6- haio-2-methyl-benzofuran-3-carboxylic acid obtained in known bromination or iodination reactions of 5-hydroxy-2-methyl-benzofuran-3-carboxylic acid ester, wherein said ester can be obtained in known reaction of p-£>enzoquinone with ethyl acetoacetate in ethanol, treated by known transesterification reaction of an aliphatic, unsaturated, cyclic, aromatic alcohol, polyglycol, in acidic or alkaline conditions and separated by a known method, ethyny!trimethylsilane and 4,4'-dihalogeno-2,2'- bipyridine.

The precursors for the synthesis of !igand 2 are following: known 2,2'- bipyridine-4,4'-dikarboaldehyd and salts of ((3,7-bis(alkoxycarbonyl)-6-methylbenzo [1 , 2-0:4, 5-b]difuran-2-yl)methyl)triphenylphosphonium obtained by a known method with a known esters of 2-(halomethyl)-6-methylbenzo[1 ,2~jb:4,5-0']difuran-3,7- dicarboxy!ic acid by reaction with triphenylphosphine in an organic solvent.

The precursors for the synthesis of ligand 3 are following: known 5H- cy openta-[1 ,2-6:5, 4-/b]dipyridin-5-one and salts of ((3,7~bis(alkoxycarbonyl)-6- methyl[1 ,2b:4,5-jb]difuran-2-yl)methyl)triphenylphosphonium obtained by a known method with a known esters 2-(halomethyl)-6-methylbenzo[1 ,2-£>:4,5-J_>']difuran-3,7- dicarboxylic acid by reaction with triphenylphosphine in an organic solvent.

The precursors for the synthesis of complexes 4, 6, 8 are following: compounds 1-3, ruthenium(lil) chloride or a dimer of dichloro(p-cymene)ruthenium(!l), 2,2 , -bipyridine-4,4 , -dicarboxylic acid and inorganic thiocyanate.

The precursors for the synthesis of complexes 5, 7, 9 are following: the compounds 1-3, ruthenium(III) chloride or a dimer of dichloro(p-cymene)ruthenium(ll) and the inorganic thiocyanate.

A method for the preparing of 6,6 , -([2,2 , -bipyndine]~4,4 , -diy])b!s (2- methylbenzo[1 , 2-0:4, 5-i>']difuran-3-carboxylic) acid (1) consists in Sonogashiry reacting 4,4'-dihalogeno-2,2'-bipyridine with ethynyltrimethylsilane in organic solvent such as aliphatic, cycloaiiphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, alcohol, ketone, ester or lactone, N-substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, in the presence of a palladium catalyst selected from the group consisting of palladium(ll) dihalides, palladium(li) acetate, palladium(ll) sulfate, palladium(ll) dichloride, bis(triphenylphosphine)- palladium(l l) dichloride, bis(tricyciopentylphosphine)palladium(ll) dichloride, bis(tricyclohexylphosphine)palladium(ll), bis(dibenzylideneacetone)palladium(0), tetrakis(triphenylphosphine)palladium(0), or most preferably [1 ,1'-bis(diphenyl- phosphino)ferrocene]dichSoropalladium(ll), with or without addition of aromatic or nonaromatic phosphine, in the presence of a copper halide and amine as a base at room temperature or higher temperature. Trimethylsilyl group in the intermediate are removed with the use of organic or inorganic fluorides or alkaline hydrolysis in mixture of water and alcohol or tetrahydrofuran. The resulting 4,4-diethynyl~2,2'-bipyndine without isolation, is reacted with an ester of 5-hydroxy-6-halo-2-methyi-benzofuran-3- carboxy!ic acid at room temperature or higher temperature to yield the ligand of formula I, which is hydrolyzed under basic or acidic conditions, and if necessary, isolating thereof using a known method.

A method for the preparing of 6,6'-((1 , 1')-[3,3'-bipyridine]-4,4'-diylbis(eteno- 2,1-diyl))bis(2-methylbenzo[1 ,2-D:4,5-o']difuran-3,7-dicarboxylic) acid (2) and esters and salts thereof, consisting in carrying the Wittig reaction of p^'-bipyridineH^'- dicarbaldehyde with ((3,7~bis(alkoxycarbonyl)-6-methyl[1 ,2b:4,5-i>]difuran-2- yl)methyl)tritnphenylphosphonium halide in an organic solvent such as an aliphatic, cycloaiiphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, alcohol, sulfoxide or a mixture of these solvents in the presence of an alkali metal hydroxide or a mixture of alkali metal hydroxides as a base at room temperature or higher temperature, which is hydrolyzed, if necessary, in basic or acidic conditions and isolated thereof using a known method.

Method for the preparing of 2-((5H-cyclopenta[1 , 2-0:5, 4-i)']dipirydyn-5- ylidene)methyl)-6"methylbenzo[1 ,2-jb:4,5-jb']difuran-3,7-dicarboxylic acid (3) and esters and salts thereof, comprising carrying out the Wittig reaction of 5H- cyclopenta[1 ,2-6:5, 4-6']dipyridin-5-one with ((3,7-bis(alkoxycarbonyl)-6-methylbenzo- [1 ,2-b:4,5-0]difuran-2-yl)methyl)tritriphenylphosphonium halide in an organic solvent such as an aliphatic, cycloaiiphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, alcohol, sulfoxide or a mixture of these solvents in the presence of an alkali metal hydroxide or a mixture of alkali metal hydroxides as a base at room temperature or higher temperature, which is hydrolyzed, if necessary, in a basic or acidic conditions and isolated thereof using a known method.

A method for obtaining of symmetrical ruthenium complexes 5, 7, 9 comprises reaction of compounds 1-3 with ruthenium(lll) chloride, or dichloro(p- cymene)ruthenium(ll) dimer and the inorganic thiocyanates in an inorganic solvent such as an aliphatic, cycloaiiphatic or aromatic hydrocarbon, aliphatic halohydrocarbon, nitrile, ether, alcohol, ketone, ester or lactone, N-substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably in N,A/-dimethylformamtde, at room temperature or higher temperature.

A method for the preparing asymmetric ruthenium complexes 4, 6, 8 comprise reacting of compounds 1-3 with 2,2'-bipyridine-4 ! 4'-dicarboxylic acid, ruthenium(lll) chloride, or a dimer of dichloro(p-cymene)ruthenium(l!) and inorganic thiocyanates in organic solvent such as aliphatic, cycloaliphatic or aromatic hydrocarbon, aliphatic ha!ohydrocarbon, nitrile, ether, alcohol, ketone, ester or lactone, N-substituted lactam, amide, cyclic urea, sulfoxide or water or a mixture of these solvents, preferably N,A/-dimethylformamide, at room temperature or higher temperature.

4,4'-Dihalogeno-2,2'-bipyridine is subjected to a Sonogashira reaction with ethynyltrimethylsilane in dry toluene in the presence of [1 ,1 '-bis(diphenylphosphino)- ferrocene]dichloropailadium(ll), copper iodide, and diisopropylamine as a base, at room temperature or higher temperature. Trimethylsilyl group in the intermediate product is removed with tetrabutylammonium fluoride. The resulting 4,4-diethynyl-2,2'- bipyridine without isolation, is reacting with an octyl ester of 5-hydroxy-6-iodo-2- methyl-benzofuran-3-carboxylic acid, at the temperature of 80°C to give a compound of formula I wherein Ri = octyl, with 96% yield without the need of purification by crystallization from an organic solvent or by column chromatography, mp = 212- 214°C.

[2,2'-B!pyridine]-4,4'-dikarboaldehyd subjecting to the Wittig reaction with a ((3,7-bis{alkoxycarbonyl)-6-methylbenzo[1 ,2-0:4,5-6 ]difuran-2-yl)methyl)tritriphenyl- phosphonium halide in isopropanol in the presence of lithium hydroxide at 60°C to give the compound 2, wherein Ri = octyl, in 92% yield after purification by column chromatography, mp = 126-128°C.

5H-cyclopenta[1 , 2-6:5, 4-6 'jdipyridin-5-one is subjecting to the Wittig reaction with ((3,7-bis(alkoxycarbonyl)-6-methylbenzo[ , 2-0:4, 5~6]difuran-2-yl)methyl)tritri- phenyiphosphonium halide in isopropanol in the presence of lithium hydroxide at 60°C to give the compound 2, wherein Ri = octyl, in 53% yield after purification by column chromatography, mp = 84-86°C.

Thus obtained ligands 1-3 are reacting with a dimer of dichloro(p- cymene)ruthenium (II), with or without addition of 2,2 , -bipyrsdyl-4,4'-dicarboxy!ic acid, in the dark in Λ/,/V-dimethylformamide, at a temperature of 140- 50°C, and then without isolation of the ammonium thiocyanate. The product is isolated using filtration, dried under reduced pressure and purified on a Sephadex LH-20, eluted with N,N- dimethylformamide. The yield of 4, after two purification on Sephadex LH-20: 36% (for RT = Et), 35% (R, = C 8 H 17 }. Yield 5, after two purification on Sephadex LH-20: 56% (RT = H). Yield 6, after two purification on Sephadex LH-20: 32% (for R 1 = Et), 51 % (Ri = C 8 H 7 ). Yield 7, after two purification on Sephadex LH-20: 59% (R-, = H). Yield 8, after two purification on Sephadex LH-20: 37% (for Ri = Et), 37% (R-, = C 8 Hi 7 ). Yield 9, after two purification on Sephadex LH-20: 57% (Ri = H). The purified compounds are black crystalline solids.

The thus obtained ruthenium complexes are insoluble in alcohols, acetonitrile, valeronitrile and other organic solvents with the exception of /V,W-dimethylformamide and dimethyisuifoxide. In order to improve solubility of the complexes, they are converted into tetrabutylammonium salts by titration with tetrabutylammonium hydroxide in ethanol to pH> 7, filtered and then titrated with dilute nitric acid(V) to pH 4-6, then ethanol was removed, washed with water at pH 4-6 and dried in vacuo over phosphorus pentoxide or in the air.

The so obtained salts are brown or black solids exhibiting absorption in the UV-Vis range both in the crystalline state and in solution. The products are stable in air and after exposure to sunlight.

Ruthenium complexes 4-9 in form of the tetrabutylammonium salts in the ethanol solution at a concentration of 1 *10 ~4 mol/dm 3 show absorption of electromagnetic radiation in the UV-Vis range. Complex 4, for Ri = Et shows three absorption maxima A max = 312 nm, 374 nm and 540 nm and a molar extinction coefficient ε = 32,036; 24,262 and 10,966 dm 3, mol "1 -cm "1 , respectively. Complex 4, for R-i = C 8 H 17 exhibits two absorption maxima A max = 374 nm (ε = 26,697 dm 3, moi "1 'cm "1 ) and A max = 542 nm (ε = 9,227 dm 3 'mor 1 , crrT 1 ). Complex 5, for Ri = H shows three absorption maxima A max = 308 nm (ε = 24,236 dm 3, mol "1 , cm "1 ) Amax - 369 nm (ε - 19,239 dm 3 mol "1 -cm "1 ) and 538 nm (ε = 8,926 dm 3 mol "1 cm "1 ). Complex 6, for Ri = Et shows three absorption maxima A max = 308 nm (ε - 30,249 dm 3, mor 1- cm "1 ) A max = 403 nm (ε = 22,560 dm 3, mor 1 , cm '1 ) and A max = 539 nm (ε = 9,770 dm 3 'mol " i cm "1 ). Complex 6, for Ri = C 8 Hi 7 shows three absorption maxima A max = 313 nm (ε = 31 ,820 dm 3 -mor 1 ' cm "1 ) A max = 408 nm (ε = 32,070 dm 3, mol "1 -cm "1 ) and 557 nm (ε = 16,441 dm 3" mor ' cm "1 ). Complex 7, for Ri = H shows three absorption maxima A max = 305 nm (ε = 27,208 dm 3 -mor 1 'cm ~1 ) A max = 402 nm (ε = 41 ,694 dm 3 moi "1 cm "1 ) and A max = 559 nm (ε = 16,389 dm 3 'moi "1 'cm "1 ). Complex 8, for Ri = Et, shows three absorption maxima A ma x = 317 nm (ε = 17,1 10 dm 3 'mor 1 'cm "1 ) A max = 403 nm (ε - 13,585 dm 3, mol " 1 cm "1 ) and A max = 529 nm (ε = 9,895 dm a mol "1 -cm "1 ). Complex 8, for Ri = C 8 H i 7 shows three absorption maxima A max = 311 nm (ε = 31 ,767 dm 3, mo 1 'cm "1 ) A ma x = 416 nm (ε = 26,760 dm 3 'mol "1 -cm "1 ) and 523 nm (ε = 8,354 dm 3 -mol " -cm "1 ). Complex 9, for Ri = H exhibits two absorption maxima A max = 315 nm (ε = 19,609 dm 3 'mo ' cm "1 ) and Amax = 440 nm (ε = 37,750 dm 3 -mor 1 cm ~1 ).

Examples

Synthesis process according to the invention is shown in the following examples, which do not limit the scope thereof.

Exampiel :

Ligand 1 according to the invention is prepared by three-step synthesis performed in a single process, without isolation of intermediates.

Octyl 6,6'-([2,2 , -bipyridine]-4,4 , -diyl)bis(2-methylbenzo[1 ,2-0:4,5-i)']difuran-3- carboxyiate) (1)

4,4'-Dibromo-2,2'-bipyridine (1.5699 g, 5 mmol), [1 ,1'-bis(diphenylphosphino)- ferrocene]dichioropalladium(ll) (0.3660 g, 0.5 mmol, 10% mol), and copper iodide (0.0952 g, 0.5 mmol, 10% mol) in a 100 ml two-necked flask equipped with a reflux condenser and a magnetic stirrer were placed under nitrogen atmosphere, and dry toluene (20 mL) was added followed by diisopropylamine (10 mL, 70 mmol) and stirred for 15 minutes. Ethynyltrimethylsilane (1.2766 g, 13 mmol) in dry toluene (5 mL) was added and heated at 80°C under a nitrogen 1.2766 atmosphere up to disappearance of etynylotrimethylsilane according to GC (2 h). After cooling to the room temperature, 1 solution of tetrabutyiammonium fluoride in dry tetrahydrofuran (13 mL) was added and stirred for 1 minute. Then, octyl 5-hydroxy-6-iodo-2-methyi- benzofuran-3-carboxylate (4.3040 g, 10 mmol) in dry toluene (50 mL) was added and stirred at 80 D C for 14 hours, it was allowed to cool to room temperature, water (40 mL) was added and the precipitate was filtered off on a Buchner funnel. The precipitate was transferred to the 250 mL flask and water (50 mL) and diethyl ether (50 mL) were added and stirred for 10 minutes. The precipitate was again filtered on a Buchner funnel and dried in vacuum over phosphorus pentoxide to yield 3.8870 g (96%) of pure product. M.p. 212-214°C. 1 H NMR (CDCI 3 , 700 MHz), δ ppm: 0.89 (t,J = 7.0 Hz, 6H, 2xCH 3 ); 1 .28-1.35 (m, 8H, 4xCH 2 ); 1 ,36-1 ,39 (m, 4H, 2xCH 2 ); 1 ,41- 1 ,45 (m, 4H, 2xCH 2 ); 1 ,51-1 ,55 (m, 4H, 2xCH 2 ); 1 ,87-1 ,91 (m, 4H, 2xCH 2 ); 2.82 (s, 6H, 2x CH 3 ); 4.41 (t,J = 7.0 Hz, 4 H, 2xCH 2 ); 7.46 (s, 2 H, 2xCH Ar ); 7.62 (s, 2 H, 2xCH Ar ); 7.80 (dd, J = 5.0 Hz, J = 1 .5 Hz, 2H, 2*CH Ar ); 8.10 (s, 2 H, 2xCH Ar ); 8.82 (d, J = 5.0 Hz, 2H, 2xCH Ar ); 8.90 (s, 2 H, 2xCH Ar ).

The solubility is too low for 3 C NMR. IR-ATR, cm "1 : 2928, 2861 , 1708, 1605, 1592, 1406, 1383, 1368, 1239, 1222, 1176, 1 151 , 1 1 17, 1091 , 1043, 988, 923, 863, 832, 808, 796, 701.

Example 2:

Ligand 2 according to the invention is prepared by a one-step synthesis.

Octyl 6,6'-((1 , 1')-[3,3 , -bipyridine]-4,4 , -diylbis(ethene-2,1-diyl))bis(2- methylbenzo[1 ,2-jb:4,5-0'3difuran-3,7-dicarboxylate) (2)

((3,7-Bis(alkoxycarbony[)-6-methylbenzo[1 ,2-ib:4,5-0]difurano-2- yl)methyl)triphenyl-phosphonium bromide (4.2042 g, 5 mmol) and lithium hydroxide monohydrate (0.4830 g, 11 .5 mmol) were placed in a 100 mL one-necked flask, equipped with a reflux condenser and a magnetic stirrer under nitrogen atmosphere in dry isopropanol (20 mL) and stirred for 5 minutes. [2,2'-Bipyridine]-4,4'- dikarboaldehyd (0.5088 g, 2.4 mmol) was added and the temperature was raised to 60°C for 5 minutes. The mixture was stirred at this temperature for 40 minutes, water (45 mL) added, filtered the resulting precipitate, which was washed with water (3x30 mL) and methanol (3 x 25 mL) and air dried to give 2.80 g of a dark orange powder. The crude product was heated in boiling p-xyiene (20 mL) containing a crystal of iodine for 1.5 hours. A part of the p-xylene (17 mL) was distilled off and methanol (40 mL) was added to the residue and stirred at reflux for 30 minutes to solidify the product. It was allowed to cool to room temperature and stirred overnight. The precipitate was filtered off, washed with methanol (2x 15 ml) and air dried to give 2.50 g (92%) of an orange product. M.p. 126-128°C. H NMR (CDCl 3 , 400 MHz), δ ppm: 0.85-0.95 (m, 12H, 4xCH 3 ); 1 ,24-1 ,48 (m, 32H, 16xCH 2 ); 1 ,50-1 ,62 (m, 8 H, 4xCH 2 ); 1 ,86-1 ,98 (m, 8 H, 4xCH 2 ); 2.82 (s, 6H, 2xCH 3 ); 4.41 (t, J = 6.9 Hz, 4 H, 2xCH 2 ); 4.47 (t, J = 6.9 Hz, 4 H, 2*CH 2 ); 7.51 (dd, J = 5.2 Hz, J = 1.2 Hz, 2H, 2xCH Ar ); 7.60 (d, J = 16.2 Hz, 2H, 2xCH Ar ); 7.99 <d, J = 3.7 Hz, 4H, 4xCH Ar ); 8.17 (d, J = 16.2 Hz, 2H, 2xCH Ar ); 8.58 (s, 2 H, 2xCH Ar ); 8.72 (d, J = 5.0 Hz, 2H, 2*CH Ar ). 13 C NMR (CDCI 3 , 100 MHz), δ ppm: 14.11 (4 x CH 3 ); 14.68 (2xCH 3 ); 22.67 (4xCH 2 ); 26.15 (2xCH 2 ); 26.28 (2xCH 2 ); 28.80 (4xCH 2 ); 29.26 (2xCH 2 ); 29.27 (2xCH 2 ); 29.30 (2*CH 2 ); 29,36 (CH2); 31.83 (4xCH 2 ); 64.58 (2xCH 2 ); 64.97 (2xCH 2 ); 102.69 (2xCH); 103.17 (2xCH); 109.09 (2xC); 110.72 {2*C); 119.23 (2xCH); 119.38 (2xCH); 120.68 (2xCH); 123.83 (2xC); ); 125.50 (2xC); 132.12 (2xCH); 144.07 (2xC); 149.16 (2xCH); 151.09 (2xC); 151.44 (2xC); 155.75 (2xC); 158.73 (2xC); 163.59 (2*0); 164.03 (2xC); 164.98 (2xC). IR-ATR cm "1 : 2923, 2854, 1705, 1605, 1588, 1554, 1401 , 1362, 1347, 1259, 1187, 150, 1082, 1052, 969, 960, 854, 820, 782, 704.

Example 3:

Ligand 3 of the invention is prepared by a one-step synthesis.

((3, 7-Bis{alkoxycarbonyl)-6-methylbenzo[1 ,2-6:4,5-6 ]difurano-2-yl)methyl)- triphenylphosphonium bromide (5.0450 g, 6 mmol) and lithium hydroxide hydrate (0.5880 g, 14 mmol) were placed in a 100 ml_ one-necked flask under nitrogen atmosphere in dry isopropanol (24 mL) and stirred for 5 minutes. 5H-cyc!openta[1 ,2- 0:5,4-6]dipyridin-5-one (1 .0920 g, 6 mmol) was added and the temperature was raised to 60°C for 15 minutes. The mixture was stirred at this temperature for 20 minutes. Water (20 mL), chloroform (100 mL) and brine (20 mL) were added and the layers were separated. The aqueous layer was extracted with chloroform (2x100 mL) and the combined chloroform layers were washed with brine and dried with anhydrous magnesium sulfate. The solvent was removed and the crude product was purified by flash chromatography on silica gel, eluted with methanol:dich!oromethane in ratio 98:2, yielding 2.11 g (53%), a pale orange crystalline solid. M.p. 84-86°C. 1 H NMR (CDCI 3 , 400 MHz), δ ppm: 0,85-0,90 (m, 6H, 2xCH 3 ); 1 ,25-1 ,46 (m, 16 H, 8xCH 2 ); 1 ,49-1 ,59 (m, 4H, 2xCH 2 ); 1 ,83-1 ,96 (m, 4H, 2xCH 2 ); 2.82 (s, 3H, CH 3 ); 4.41 (t, J = 6.79 Hz, 2H, CH 2 ); 4.48 (t, J = 6.7 Hz, 2H, CH 2 ); 7.33 (dd, J = 8.0 Hz, J = 4.8 Hz, 1 H, CH Ar ); 7.42 (dd, J = 8.0 Hz, J = 4.8 Hz, 1 H, CH Ar ); 8.05 (d, J = 0.4 Hz, 1 H, CH Ar ); 8.15 (dd, J = 8.0 Hz, J = 1.2 Hz, 1 H, CH Ar ); 8.17 (s, H, CH Ar ); 8.43 (s, H, CH Ar ); 8.74 (dd, J = 4.8 Hz, J = 1.2 Hz, 1 H, CH Ar ); 8.76 (dd, J = 4.8 Hz, J = 1.2 Hz, 1 H, CH Ar ); 9.12 (dd, J = 8.0 Hz, J = 1.2 Hz, 1 H, CH Ar ). 3 C NMR (CDCI 3 , 100 MHz), δ ppm: 14.07 (2 x CH 3 ); 14.93 (CH 3 ); 22.64 (2><CH 2 ); 26.19 (2xCH 2 ); 28.75 (CH 2 ); 28.79 (CH 2 ); 29.21 (CH 2 ); 29.23 (CH 2 ); 29.31 (2xCH 2 ); 31.81 (2xCH 2 ); 64.72 (CH 2 ); 65.35 (CH 2 ); 102.67 (CH); 103.75 (CH); 109.09 (C); 113.82 <CH); 114.15 (C); 122.98 (2*CH); 123.23 (C); 127.01 (C); 127.92 (CH); 130.15 (C); 132.97 (C); 133.99 (CH); 134.51 (C); 150.56 (CH); 150.68 (CH); 151.39 (C); 151.73 (C); 156.45 (C); 156.87 (C); 158.74 (C); 163.33 (C); 163.85 (C); 165.52 (C).). IR-ATR, cm "1 : 2922, 2853, 1705, 1416, 1395, 1348, 1262, 1243, 1 192, 1147, 1089, 1056, 963, 894, 855, 813, 806, 781 , 745, 724, 705.

Example 4:

Complex 4 according to the invention is prepared by a one-step synthesis.

Mixture of dichioro(p-cymene)ruthenium (II) dimer (0.3062 g, 0.5 mmol) and octyl 6,6'-([2,2'-bipyridine]-4,4'-diyl)bis(2-methylbenzo [ ,2-0:4,5-0]difuran-3- carboxylate) (0.8090 g, 1 mmol) in dry W,W-dimethylformamide (40 ml_) was heated in the dark at 150°C for 2 hours, monitoring the disappearance of substrate using a UV- Vis spectrometry. 2,2'-Bipyridine-4,4'-dicarboxylic acid (0.2442 g, 1 mmol) was added and stirred at 150°C for a further 4 hours. Ammonium thiocyanate (2.74 g, 36.5 mmol) was added and stirred at 150°C for another 4 hours. It was cooled to room temperature, the precipitate was filtered off and W,W-dimethylformamide removed using a rotary evaporator. To the residue water (100 mL) was added and the precipitate filtered. The precipitate was washed with more water (100 mL) and dried to give 0.985 g of crude product. The product was purified twice on Sephadex LH-20, eluted with W,W-dimethylformamide and the main band collected to yield 0.440 g (35%) of black, glossy product. The total product was taken up in ethanol and titrated with 0.5 M aqueous solution of tetrabutylammonium hydroxide up to pH = 9. The mixture was stirred for 5 minutes, filtered, acidified with 0.01 M HN0 3 to pH = 5.2 and the solvents were removed. The resulting precipitate was washed with water at pH 5.2 and dried to give the tetrabutylammonium salt as a black powder, M.p 300°C. Due to the complex mixture of diastereomeric products NMR spectra were unreadable. IR-ATR, cm "1 : 2962, 2935, 2856, 2100, 1707, 161 1 , 1467, 1426, 1402, 1362, 1305, 1235, 1 176, 1083, 1019, 979, 921 , 853, 807, 782, 705, 473.

Example 5:

The complex 5 of the present invention is prepared by a one-step synthesis. Mixture of dichloro(p-cymene)ruthenium(ll) dimer (0.3062 g, 0.5 mmol) and 6,6 l -([2,2 , -bipyridine]-4,4'-diy[)bis(2-methylbenzo[1 ,2-0:4,5-0]d!furan-3-carboxy^ acid) (1.1691 g, 2 mmoi) in dry Λ/,/V-dimethyiformamide (40 mL) was heated in the dark, at a temperature of 150°C for 4 hours, monitoring the disappearance of substrate using a UV-Vis spectrometry. Ammonium thiocyanate (2.74 g, 36.5 mmol) was added and stirred at 150°C for another 4 hours. It was cooled to room temperature, the precipitate was filtered off and /V,/V-dimethylformamide removed using a rotary evaporator. Water (100 mL) was added to the residue and the precipitate was filtered. The precipitate was washed with more water (100 mL) and dried to give 0.985 g of crude product. The product was purified twice on Sephadex LH-20, eluted with Λ/,/V-dimethylformamide and the main band collected to yield 0.775 g (56%) of black, glossy product. The total product was taken up in ethanol and titrated with 0.5 M aqueous solution of tetrabuty!ammonium hydroxide up to pH = 9. The mixture was stirred for 5 minutes, filtered, acidified with 0.01 M HNO3 to pH = 5.2 and the solvents were removed. The resulting precipitate was washed with water at pH 5.2 and dried to give the tetrabutylammonium salt as a black powder, M.p.> 300°C. Due to the complex mixture of diastereomeric products NMR spectra were unreadable. IR-ATR, cm "1 : 2962, 2935, 2103, 1707, 1611 , 1426, 1402, 1362, 1236, 1176, 1083, 1017, 980, 922, 854, 809, 705, 473.

Example 6:

Complex 6 according to the invention is prepared by a one-step synthesis.

Mixture of dimer of dichloro(p-cymene)ruthenium (II) (0.3062 g, 0.5 mmol) and octyi 6,6'-((1 ,rH3 l 3'-bipyridine]-4,4 , -diytbis(eteno-2, 1-diyl))bis(2- methylbenzo[1 ,2-b:4,5-6']difuran-3,7-dicarboxylate) (1.1734 g, 1 mmol) in dry N,N- dimethylformamide (40 mL) was heated in the dark at 150°C for 2 hours, monitoring the disappearance of substrate using a UV-Vis spectrometry. 2,2'-Bipyridine-4,4'- dicarboxylic acid (0.2442 g, 1 mmol) was added and stirred at 150°C for 4 hours. Ammonium thiocyanate (2.74 g, 36.5 mmol) was added and stirred at 150°C for a further 4 hours. Mixture was cooled to room temperature, the precipitate was filtered off and N,W-dimethylformamide removed using a rotary evaporator. Water (100 mL) was added to the residue and the precipitate filtered. The precipitate was washed with more water (100 mL) and dried to give 1 .182 g of crude product. The product was purified twice on Sephadex LH-20, eluted with /V-dimethylformamide and the main band collected to yield 0.834 g (51%) of b!ack, glossy product. The total product was taken up in ethanoi and titrated with 0.5 M aqueous solution of tetrabutyiammonium hydroxide up to pH = 9. The mixture was stirred for 5 minutes, filtered, acidified with 0.01 M HN0 3 to pH = 5.2 and the solvents were removed. The resulting precipitate was washed with water at pH 5.2 and dried to give the tetrabutyiammonium salt as a black powder, M.p.> 300°C. Due to the complex mixture of diastereomeric products NMR spectra were unreadable. IR-ATR, cm "1 : 2960, 2923, 2853, 2097, 1705, 1601 , 1360, 1246, 1181 , 1057, 960, 861 , 781 , 473.

Example 7:

Complex 7 according to the invention is prepared by a one-step synthesis.

Mixture of dimer of dichloro(p-cymene)ruthenium (II) (0.3062 g, 0.5 mmoi) and 6,6'-((1 ,1 , H3,3 , -bipyridine]-4,4 , -diy[bis(eteno-2,1-diyl))bis(2-methylbenzo[1 J 2- 6:4,5-jf>']difuran-3,7-dicarboxy!ic) acid (1.4492 g, 2 mmol) in dry N,N- dimethylformamide (40 ml_) was heated in the dark at 150°C for 4 hours, monitoring the disappearance of substrate using a UV-Vis spectrometry. Ammonium thiocyanate (2.74 g, 36.5 mmol) was added and stirred at 150°C for another 4 hours. The mixture was cooled to room temperature, the precipitate was filtered off and N,N- dimethylformamide removed using a rotary evaporator. Water (100 mL) was added to the residue and the precipitate filtered off. The precipitate was washed with more water (100 mL) and dried to give 1.305 g of crude product. The product was purified twice on Sephadex LH-20, eluted with Λ/,Ν-dimethylformamide and the main band collected, yielding 0.9150 g (59%) of black, glossy product. The total product was taken up in ethanoi and titrated with 0.5 M aqueous solution of tetrabutyiammonium hydroxide up to pH = 9. The mixture was stirred for 5 minutes, filtered, acidified with 0.01 M HNO3 to pH = 5.2 and the solvents were removed. The resulting precipitate was washed with water at pH 5.2 and dried to give the product as a black powder, M.p.> 300°C. Due to the complex mixture of diastereomeric products NMR spectra were unreadable. IR-ATR, cm "1 : 2960, 2922, 2099, 1972, 1694, 1599, 1419, 1362, 1243, 1 172, 1046, 954, 861 , 81 1 , 722.

Example 8:

Complex 8 according to the invention is prepared by a one-step synthesis. Dinner dichloro(p-cymene)ruihenium (il) (0.1531 g, 0.25 mmol) and ester octyl ester 2-((5H-cyclopenta[ ,2~0:5,4"i ']dipirydyn-5-ylidene)methyl)-6-methyibenzo[1 ,2- 0:4,5-0']difuran-3,7-dicarboxylic (0.3314 g, 0.5 mmol) in dry /V,A/-dimethylformamide (20 mL) was heated in the dark at 150°C for 2 hours, monitoring the disappearance of substrate using a UV-Vis spectrometry. Was added 2,2'-bipyridine-4 1 4'-dicarboxy]ic acid (0.1221 g, 0.5 mmol) and stirred at 150°C for 4 hours. Was added ammonium thiocyanate (2.74 g, 36.5 mmol) and stirred at 150°C for a further 4 hours. Coo! to room temperature, the precipitate was filtered off and remove N,/V-dimethyIformamide on a rotary evaporator. To the residue was added water (50 mL) and filter the precipitate. The precipitate was washed with more water (50 mL) and dried to give 0.311 g of a crude brown product. The product was purified twice on Sephadex LH- 20, eiuted with N,/V-dimethylformamide and the main band collected to yield 0.206 g (37%) of black, glossy product. The total product was taken up in ethanol and titrated with 0.5 M aqueous solution of tetrabutylammonium hydroxide up to pH = 9.

The mixture was stirred for 5 minutes, filtered, acidified with 0.01 HN0 3 to pH = 5.2 and the solvents were removed. The resulting precipitate was washed with water at pH 5.2 and dried to give the tetrabutylammonium salt as a black powder, mp> 300°C. Due to the complex mixture of diastereomeric products N R spectra were unreadable. IR-ATR cm "1 : 2960, 2939, 2859, 2102, 1970, 1708, 1601 , 1404, 1364, 1244, 190, 1064, 958, 866, 810, 782, 749, 702, 676, 473.

Example 9:

Complex 9 according to the invention is prepared by a one-step synthesis.

The mixture of dimer of dichloro(p-cymene)ruthenium (II) (0.3062 g, 0.5 mmol) and 2-((5H-cyclopenta[1 ,2- :5,4-b']dipirydyn-5-yiidene)methyl)-6- methylbenzo[1 ,2-0:4,5-0']difuran-3,7-dicarboxy!ic acid (0.8768 g, 2 mmol) in dry N,N- dimethylformamide (40 mL) were heated in the dark at 150 D C for 4 hours, monitoring the disappearance of substrate using a UV-Vis spectrometry. Ammonium thiocyanate (2.74 g, 36.5 mmol) was added and stirred at 150°C for a further 4 hours. The mixture was cooled to room temperature, the precipitate was filtered off and N,N- dimethylformamide removed using a rotary evaporator. Water (100 mL) was added to the residue and the precipitate filtered. The precipitate was washed with more water (100 mL) and dried to give 0.872 g of crude product. The product was purified twice on Sephadex LH-20, eluted with Λ/,/V-dimethyl-formamide and the main band collected, yielding 0.6237 g (57%) of black, glossy product. The total product was taken up in ethanol and titrated with 0.5 M aqueous solution of tetrabutylammonium hydroxide up to pH = 9. The mixture was stirred for 5 minutes, filtered, acidified with 0.01 M HN0 3 to pH = 5.2 and the solvents were removed. The resulting precipitate was washed with water at pH 5.2 and dried to give the product as a black powder, M.p.> 300°C. Due to the complex mixture of diastereomeric products NMR spectra were unreadable. IR-ATR cm "1 : 2962, 2932, 2877, 2107, 1969, 1700, 1603, 1413, 1362, 1183, 1049, 954, 868, 809, 756, 644, 568, 455.