OLIGOHETEROARENES WITH STEREOGENIC AXES"

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DESCRIPTION

Technical Background

Electro-active materials used, for example, in the manufacture of devices for the electronics field, the sensors field and the photovoltaics field, are usually conjugated linear polymers or oligomers, mainly thiophene-based. Key parameters for their performance and use in the above-mentioned fields are the regioregularity, the homogeneity of molecular weights, the tridimensional structure, the chemical stability, the processability and costs. The most well-known example of this group of materials is regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT), with a M _n comprised between 54,000 and 75,000 (expressed as number average Molecular Weight and defined as the total weight of all polymer molecules of a given sample, divided by the total number of polymer molecules in the same sample) presenting a very high conductivity (about 10 ³ S/cm) after iodine doping. Neutral polyconjugated systems, also known as pristines, are insulating materials which become conductors following a process, defined doping, usually an oxidation process, that can be carried out with iodine or by means of a reduction process. Such systems provide radical cation or radical anion species wherein the electron mobility is enhanced. Some interesting properties of the above-mentioned electro-active materials are connected to the effects induced by the alkyl chains, such as the tridimensional structure, favoring the space filling, and the solubility in organic solvents, which allows to easily process the material. However PHT may undergo degradative effects at the terminal positions of the chains and it is very expensive, even if purchased in bulk form (at the moment of patent filing, about 300 Euro/g), as a consequence of the synthesis processes and, especially, of the technologically complex purification. For these reasons, the actual trend is to address, instead of polymers made of chains with possible highly different lengths, structural defined molecules such as, e.g., suitably derivatized oligomers with a well-defined length. In the specific case, a typical example is represented by oligothiophenes (above all sexthiophene), optionally "capped" at the terminal positions with protecting groups. However, these compounds are quite expensive as well if it is considered that unsubstituted sexthiophene, poorly usable as such due to its insolubility, has a cost of about 150 Euro/g at the moment of patent filing.

A solution to all the above-mentioned technical and scientific problems could be provided by macrocyclic oligoarenes or oligoheteroarenes, e.g. by macrocyclic oligothiophenes: these compounds can mimic polymer with an infinite length, are free of terminal positions since they are cyclic, they are very stable, are more soluble than linear oligomers even if the few known members of this series are characterized by the presence of alkyl chains, in particular «-butyl chains. Finally, they have cavities of various sizes and shapes according to the size of the ring, which are able to host molecules on their inside capable of creating specific interactions.

Actually, the use of macrocyclic oligoarenes and oligoheteroarenes presents some insuperable problems, in particular if they are considered for a possible industrial application, mainly due to drastic difficulties found in currently available methods for their preparation. As a matter of fact, the synthesis of these compounds requires to start from monomers which are themselves already difficult to be obtained, because they are prepared through synthesis schemes requiring several steps involving expensive and hardly-handling reagents. Once the monomer has been obtained, it must be suitably derivatized; i.e., it is necessary to introduce, at the terminal parts of the molecule, the reactive functional groups which can give origin to the cyclization reaction. This derivatization process also requires to perform several difficult synthesis steps. As expected, the cyclization reaction leads to the formation of mixtures of different macrocycles, depending on the number of monomers present in the so-obtained different macrocycles. The macrocycles mixtures have to be resolved, i.e. the different macrocycles must be separated from one another. Currently, the most used separation technique is HPLC separation (High Performance Liquid Chromatography). By following this method, approximately, the yields of the macrocyclization reaction alone, leading to intermediates prone to be further converted in macrocyclic oligothiophenes, are comprised in a range between 2% and 12%. Such yields are therefore completely unsatisfactory and unacceptable from an industrial point of view.

For example in the specific case macrocyclic oligothiophenes, some of the thiophene rings constituting the intermediate macrocycle are obtained, once the cyclization occurred, by reacting diacetylene systems which, under suitable conditions, react with sodium sulfide forming thiophene rings. Such additional step further drastically reduces the yields of the final macrocycles.

The so obtained macrocyclic products have only alpha-alpha' type bonds, i.e. the different thiophene rings are all linked together in the alpha position with respect to the S atom.

An example of a synthetic strategy employed for the preparation of an oligothiophene macrocycle is reported in the following:

SCHEME 1

The two tert- and penta-thiophene compounds bringing, at the terminal positions, two acetylene groups undergoing the macrocyclization process are prepared starting from commercially available, but expensive (more than 10 Euro/g if purchased in bulk form) 3,4-dibromothiophene, by. means of reaction sequences made of six and eight steps respectively, which are often technologically complex and require expensive, highly flammable and toxic reagents, such as trimethylsilylacetylene, with global yields lower than 30%.

The macrocyclization reactions carried out on the two diacetylene derivatives lead to macrocycle mixtures, which can be separated by preparative HPLC with very low yields, as reported in the following Table 1 :

The above-described macrocycles must be then converted to the macrocyclic oligothiophenes by reacting with sodium sulfide, as shown in Scheme 2 reported in the following. The yields, ranging from 7% to 27%, are moderate even if in agreement with the expectations.

As a practical example, the preparation method of the macrocyclic oligothiophene reported above with m=3, which is the one obtained with the highest yields in the final step, prepared according to the known art, gives an overall yield below 0.6%. For example, starting from 1 Kg of 3,4-dibromothiophene, i.e. the starting product, few tens mg of the final oligothiophene macrocycle are obtained.

It is therefore clear that such methods are totally unsuited and cannot be used from an industrial or semi-industrial preparative point of view.

For example, a further disadvantage connected to the actually available macrocyclic oligothiophenes, is related to the fact that these products must necessarily have substituerit groups, usually alkyl groups, such as e.g. «-butyl groups or phenyl groups, on the macrocyclic structure in order to increase the solubility which, without such groups, would be most likely very low being comparable to that of linear oligothiophenes. The presence of such substituent groups, however, makes the synthesis method of these compounds even more complex and contributes to further reduce the yields. Moreover, still the presence of such groups leads to a final macrocycle with high molecular weights, with a reduction of the weight of the electro-active part with respect to the total molecular weight, with further disadvantages connected to such aspect.

The structural and synthetic problems highlighted above become even more complex when it is desired to employ chiral materials of this type, which offer further application potentials in the manufacture of electro-chiroptical devices, of sensors for chiral analytes, as well as of chiral stationary phases for the enantioselective chromatography. Considering that electro-active poly conjugated macrocycles have never been synthesized, the chirality is usually introduced in linear oligothiophenes and polythiophenes by decorating the monomer units, which are going to constitute the oligomer or the polymer, with chiral groups, usually characterized by a stereocenters. The chirality expressions in these materials are usually moderate and separated from electrical properties, because the chiral substituents are on the outer part of the conjugated chains responsible for the electro-conductivity which result to be only asymmetrically perturbed and not inherently dissymmetric.

Objects of the Invention Object of the present invention is to provide new electro-active, optionally chiral, polyconjugated macrocyclic compounds, optionally usable as single enantiomers, which are easily attainable by a synthetic route and that can be obtained in high amounts.

Also object of the present invention is to provide new electro-active, further chiral, polyconjugated macrocyclic compounds, optionally usable as single enantiomers, which can be obtained by economically convenient and easily achievable on a preparative, semi-industrial or industrial scale, synthetic methods.

Still object of the present invention is to provide new electro-active, further chiral, polyconjugated macrocyclic compounds, optionally usable as single enantiomers, which are soluble in most of the organic solvents, then easily processable for the manufacture of devices.

Still object of the present invention is to provide new electro-active, further chiral, polyconjugated macrocyclic compounds, optionally usable as single enantiomers, which could be variously derivatized in order to make them suitable for the expected uses.

Still object of the present invention is to provide new electro-active, further chiral, polyconjugated macrocyclic compounds, optionally usable as single enantiomers, which can be used in the manufacture of devices for the electronics field, the optoelectronic field, the sensors field and the photo voltaics field.

Also object of the present invention is to provide new electro-active, also chiral, polyconjugated macrocyclic compounds that can be used optionally as single enantiomers, which can be generally used in the catalysis and, in particular, in the stereoselective catalysis.

Description of the Invention

These and still other purposes are obtained by the present invention whose object, according to one of the aspects thereof, are electro-active macrocyclic oligoarenes and oligoheteroarenes wherein the monomelic units are compounds characterized by at least one stereogenic axis consisting of a biaromatic/biheteroaromatic atropisomeric skeleton which is substituted with at least two substituents at the ortho position with respect to the inter-ring bond, each of said substituents being constituted by at least one aromatic/heteroaromatic ring conjugated to said atropisomeric skeleton.

According to the present invention, the term "oligoarenes" means a variable length sequence, however with a length generally not greater than one hundred units, of carbocyclic aromatic rings inter-connected in such a way to keep continuous the conjugation between them and between them and the aromatic and heteroaromatic rings constituting the atropisomeric units, whereas the term "oligoheteroarenes" means a sequence of heterocyclic aromatic rings or mixed carbocyclic and heterocyclic rings, interconnected in such a way to keep continuous the conjugation between them and between them and the aromatic or heteroaromatic rings constituting the atropisomeric units.

Still according to the invention, the term "electro-active" means compounds which become conductors following a process, defined doping, which can provide radical cation or radical anion species in which the electron mobility is enhanced.

Still according to the invention, "stereogenic axis" means a molecule moiety of the monomer in which it is possible to identify a rigid tridimensional combination of atoms of the kind reported below, in which the sequences A-X-B and C-Y-D identify two nearly orthogonal axes groups of atoms).

In said structure, the X and Y atoms can be the same or different, the pairs of groups A-B and C-D can be the same or different whereas, within said pairs, the A and B groups, and the C and D groups, must be different. Molecules possessing a stereogenic axis are those usually characterized by a biaromatic/biheteroaromatic "atropisomeric skeleton" which is substituted with at least two substituents at the ortho position with respect to the inter-ring bond, represented by the X- Y bond in the scheme.

With the term compounds with an "atropisomeric skeleton" is meant, according to the present invention, compounds possessing one or more biaromatic carbocyclic groups, biheteroaromatic groups or mixed carbocyclic-heterocyclic aromatic groups, which are substituted with at least two substituents at the ortho position with respect to the inter-ring bond characterized in that, at room temperature, the rotation about the inter-ring bond connecting the two aromatic or heteroaromatic systems, is substantially hindered.

With the term "inter-ring bond" is meant, still according to the present invention, the bond connecting the two aromatic or heteroaromatic systems around which the rotation is hindered.

Still according to the present invention, said biaromatic/biheteroaromatic atropisomeric skeleton is advantageously selected from the following compounds:

Biphenyl

3,3'-bithiophene

2,2'-bipyrrole

3,3'-bipyrrole

3,3'-bifurane

and possible benzo-fused derivatives thereof.

Preferred, according to the invention, is the atropisomeric skeleton constituted by of 3,3'-bibenzothiophene, 2,2'-bipyrrole and Ι, 1`-binaphthyl.

Still according to the present invention, preferred monomeric compounds are those as set forth in the following general formula I and in particular II.

Said monomers are generally attainable starting from commercial products of moderate cost through synthetic sequences made of few steps proceeding with generally satisfactory yields, exemplified in the following Figure 1 referring to the synthesis of compound II. The starting product for the synthesis, thianaphthene, has a current cost of few hundreds of Euro per kg.

Monomers having the general structure described above are transformed into macrocycles by chemical, as well as electrochemical, oxidation reactions, carried out either directly on them or on products thereof obtained by double-deprotonation with salts of high oxidation state metals, e.g. ferric chloride.

In Figure 2 below it is reported the general scheme for the macrocycle formation and, in particular, for the formation of dimer III and trimer IV of II. The formulas highlight the connectivity, but not the stereochemistry, of the molecules, which are tridimensional having the first one two stereogenic axes and the second one three stereogenic axes, according to the definition of stereogenic axis provided above.

FIGURE 2

In the following Figure 3, other monomers are reported that can generate macrocycles by oxidation.

FIGURE 3

The electro-active macrocyclic oligoarene and oligoheteroarene compounds of the present invention have several and significant advantages with respect to the electro- active compounds with a linear skeleton available according to the known art. In particular, because these are cyclic compounds, they do not present terminal moieties which are reactive and susceptible to possible undesired degradations, and they also do not require any substitution usually carried out on the macrocycles of the known art with alkyl groups in order to improve solubility thereof, since they are already completely and surprisingly soluble in most organic solvents. Indeed, in the absence of any substitution on the macrocyclic chain, macrocycles according to the invention are soluble in the most commonly used polar or apolar organic solvents, e.g. selected from chlorinated solvents, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), both aliphatic and aromatic chlorinated solvents in general, aromatic hydrocarbons, such as toluene and xylenes. This aspect represents a remarkable advantage of the compounds according to the invention with respect to macrocycles according- to known art, because the presence of substituents, e.g. alkyl ones, on the currently known macrocycles, although useful to make soluble the compounds, significantly increases the molecular weights thereof, leading to a reduction of the electro-active part of the molecule with respect to the inert part consisting of the alkyl functionalities. For example, in P3HT, more than 50% of the weight is made of inert, hexyl-groups, and only the remaining part is made of electro-active polythiophene. Moreover, synthesis methods of the macrocyclic systems are very complex, disadvantageous from an economic point of view and impossible on an industrial scale. On the opposite, the compounds according to the invention are generally soluble in most of the organic solvents, even without the above mentioned alkyl substituents, have the advantage of being well defined molecules rather than mixtures of polymeric chains of different lengths, of having electro-active molecular moieties greater than those of the corresponding known macrocycles, of having high tridimensional structure providing a high capacity of filling the available space, and of being easily prepared by means of economically favorable methods, on a preparative, semi-industrial and industrial scale.

The electro-active macrocyclic oligoarenes and oligoheteroarenes according to the present invention have cavities adapted to "host" full molecules and/or metals of various type. Moreover, because they are electro-active, they undergo changes in the molecular geometry on varying the charge thereof and, therefore, they can adopt different conformations, thus being extremely versatile compounds from a structural point of view.

A novel characteristic of the compounds object of the invention concerns the fact that they can be both achiral and chiral. Differently from the electro-active macrocyclic compounds according to the known art, which are not chiral, or from the electro- active linear systems wherein the chirality is conferred by the presence of substituents found on their structure, which are introduced during the synthesis method thus leading to significant difficulties from a synthetic point of view, by lowering the reaction yields and requiring the purification of the different mixtures of the so-obtained compounds, the compounds according to the invention are chiral without any chiral substituent, because the geometry thereof confers chirality to the system. This is due to the fact the inter-ring bond characterizing the monomelic atropisomeric skeleton, corresponding to the stereogenic axis, makes the formed macrocycle chiral "in itself, without the need of conferring chirality to the final compound by the presence of additional chiral groups in the form of chain substitutions.

Still according to the present invention, within the monomeric unit as defined above, both the rings forming the biaromatic/biheteroaromatic atropisomeric skeleton and every substituent on this, which is made of at least one, preferably electron-rich, aromatic/heteroaromatic ring conjugated to said skeleton, can be variously functionalized in order to confer specific properties to the final macrocyclic compounds.

When said substituents of the monomeric unit consist of more than one, preferably electron-rich, aromatic/heteroaromatic ring conjugated to said skeleton, in order to make electro-active the final macrocyclic compounds, it is required that every ring is conjugated to the other one and that all the rings are conjugated to the atropisomeric system. In other words, it can be said that the whole system must be "polyconjugated".

According to the present invention it is preferred the monomeric unit consisting of 3,3'-dibenzothiophene substituted at positions 2 and 2' with 5-(2,2'-dithiophene) units, as set forth in formula III.

Also preferred is the monomeric unit consisting of 3,3'-dibenzothiophene substituted at positions 2 and 2' with 5-(2,2',5',2"-tert-thiophene) units, as set forth in formula IV.

Also preferred is the monomeric unit as set forth in the following formula XIV:

Still according to the present invention, the monomeric unit as set forth in formula XV is a preferred form according to the following formula:

The electro-active macrocyclic oligoarene and oligoheteroarene compounds according to the present invention are advantageously used in the manufacture of devices for the electronics field, the sensors field, the photo voltaics field or in stereoselective catalysis reactions.

The method for the manufacture of the electro-active macrocyclic oligoarene and oligoheteroarene compounds according to the invention comprises the following steps, as reported in Figure 4:

1- Synthesis of a racemic monomer having the general formula (I) or, in particular, as reported in Figure 3;

2- Possible resolution of the racemic monomer in antipodes, carried out either by chiral column chromatography or by standard methods with diastereoisomers when the monomer has functional groups that can be used for this purpose.

3- Oxidation of said enantiopure or racemic monomer, with usually inorganic oxidants (OX ₁ ) such as ferric chloride, vanadyl chloride, arsenic pentachloride, etc. It is also possible to carry out the oxidation by electrochemical oxidation by means of an anodic oxidation process on suitable electrode surfaces.

4- Reduction of the organic material oxidised to neutral with a reducing species, such as hydrazine hydrate, sulfites, etc.

5- Recovery of the organic fraction by filtration.

6- Hot continuous extraction of the organic fraction with organic solvent, such as THF, dioxane, chlorobenzene, toluene, xylene, etc.

7- Column chromatography, usually with silica gel or neutral alumina, for the dimers, trimers, tetramers, etc., separation.

FIGURE 4

Alternatively, if the terminal rings of the monomer have acid hydrogens that can be deprotonated with strong bases or groups which can undergo transmetalation to give dianions, the oxidation according to step 3 of the above sequence is performed on the monomer dianion. Oxidants, in the present case (OX ₂ ), are milder, such as copper (II) chloride, cobalt chloride, silver oxide, etc.

The procedure then follows the same sequence 4-7 reported above.

As already illustrated in detail above, object of the present invention is new, both achiral and inherently chiral and electro-active, macrocyclic oligoarenes and oligoheteroarenes, which can be prepared by means of a synthesis method consisting of few simple steps.

The synthetic strategy involves the preparation of an oligomer provided with a defined stereochemistry (open blade scissors-shaped), undergoing a direct cyclo- oligomerization process (the ends of the scissors blades connect with those of another scissors to provide a cyclo-dimer or, sequentially, to other two to provide a cyclo-trimer and so on).

The monomer is characterized by an atropisomeric biarylic or biheteroarylic scaffold with a stereogenic axis (the inter-ring bond is the pivot of the scissors) having two groups made of a variable length series of aromatic or heteroaromatic rings (the two blades of the scissors).

The reagent, e.g. ferric chloride, acts both as templating agent and oxidizer: it associates to terminal parts of two monomer molecules carrying out the oxidative coupling thereof (connection of two tips of two different scissors) to give a dimer in which the further complexation keeps the vacant terminal parts in a favorable reciprocal position with respect to any closure.

If the monomer is enantiopure, all the derived cyclo-oligomers are enantiopure. The monomer is inherently chiral, i.e. the chirality thereof does not depend, as already mentioned, upon chiral substituents connected to the electrically conductive chain, but it is the torsion within the chain itself of the atropisomeric structure that generates the system dissymmetry. The same consideration is valid for the cyclo- oligomers which are all inherently chiral.

The present invention consist of realizing, by means of simple synthetic methods, inherently chiral macrocyclic oligoarenes and oligoheteroarenes, that can be used both as enantiopure stereoisomers, racemic mixtures, and diastereoisomers mixture. Each stereoisomer, or stereoisomers mixtures as defined herein are object of the present invention.

The invention will be now illustrated by means of non-limiting examples provided to better illustrate the invention. '

EXPERIMENTAL SECTION

4,4'-Bis (2,2'-bithiophene-5-yl)-2,2',5,5'-tetramethyI-3,3'-bithiophe ne (VII)

To a solution of 4,4'-dibromo-2,2',5,5'-tetramethyl-3,3'-bithiophene (1.6 g) and Pd(PPh ₃ ) ₄ (0.95 g) in toluene (25 ml), under stirring and inert atmosphere, trimethylstannyl-bythiophene (2.70 g) was added. The reaction mixture is heated under reflux. The solvent is evaporated under reduced pressure. The residue is taken- up with CH ₂ C1 ₂ and purified by silica gel chromatography, by using as eluent hexane at first and then a mixture containing increasing amounts of hexane. Monomer VII, a yellow solid, is crystallized from diisopropyl ether (0.61 g, yield: 26.8%); m.p. 144.2-145; 1H NMR (300 MHz; CDC1 ₃ ): δ 7.13 (2H, dd, J (H,H) = 1.04 Hz, J (H,H) = 4.8 Hz,), 7.0 (2H, dd, J (H,H) = 0.99 Hz, J (H,H) = 2.56 Hz), 6.95 (2H, dd, J ₁ (H,H) = 1.37 Hz, J ₂ (H,H) = 5.058 Hz), 6.91 (2H, d, J (H,H) = 3.7), 6.35 (2H, d, J (H,H) = 3.7 Hz), 2.45 ( 6H, s), 2.15 (6H, s); MS (EI): 550 (M+, 100%), 330 (30%) General procedure for the synthesis of compounds IX, X, XII and XIII

A mixture of 2,2'-dibromo-3,3'-bithianaphtene (1 mmol), suitable 2-trimethylstannyl derivative (1.2 mmol) and Pd(PPh ₃ ) ₄ in toluene (20 mL) is heated under reflux and inert atmosphere for 24 hours. The solvent is removed under reduced pressure and the residue is subjected to silica gel chromatography with a suitable eluent to isolate the pure monomer.

2,2'-Bis-(2-{4-[7-(2-thienyl )benzo[c][l,2,5]thiadiazolyl ]}thienyI)-3,3'- bithianaphtene (XIV)

Gravimetric chromatography using as eluent a hexane/CH ₂ C1 ₂ -7/3 mixture to give monomer XIV as dark red solid (yield 45%); 1H NMR (300 MHz; DMSO-d ₆ ): δ 8.17 (1H, d, J = 8.1 Hz), 8.05 (1H, d broad, J = 3 Hz ), 7.92 (1H, d, J = 3.6 Hz ), 7.90 (lH,s broad), 7.73 (1H, d broad, J= 1.8 Hz), 7.71 (1H, s broad), 7.46 (1H, t, 7.8 Hz), 7.32 (2H, m), 7.20 (2H, m); MS (EI+): m/z: 861.

2,2'-Bis[(3',4'-dibutyl)-5,2 ^, ,5',2"-tert-thiophen-2-yI]-3,3'-bithianaphtene (XV) Flash chromatography using as eluent a hexane/CH ₂ C1 ₂ -8/2 mixture to give monomer XV as orange solid (yield 25%); 1H NMR (300 MHz; CDC1 ₃ ): δ 7.95 (1H, d, J= 6 Hz), 7.40 (1H, t, J= 6 Hz), 7.34 (1H, d, J= 3 Hz), 7.27 (3H, m), 7.12 (1H, d, J= 3 Hz), 7.08 (1H, t, J = 3 Hz), 7.00 (1H, d, J= 3 Hz), 2.65 (2H, t, J= 6 Hz), 2.52 (2H, t, J = 6 Hz), 1.35 (8H, m), 0.95 (3H, t, J= 6 Hz), 0.86 (3H, t, J= 6 Hz).

2,2'-Bis[2-(4,4'-dihexyl-cyclopenta[2,l-b:3,4-b']dithieny l)]-3,3'-bithianaphtene (IX)

Silica gel flash chromatography using as eluent a hexane/CH ₂ C1 ₂ 95/5 mixture to give monomer IX as glassy yellow solid (yield: 38%); m.p.: 54-55°C; 1H NMR (300 MHz; acetone-d ₆ ): δ 7.98 (d, J(H,H) = 7.98 Hz, 2H), 7.37 (t, J (H,H) = 7.98 Hz, 2H), 7.28 (d, 3 (H,H) = 4.85 Hz, 2H), 7.25 (t, J (H,H) .= 7.98 Hz, 2H), 7.18 (d, J (H,H) = 7.98 Hz, 2H), 7.12 (s, 2H), 7.28 (d, J (H,H) = 4.85 H z, 2H), 1.78 (m, 8H), 1.06 (m, 24H) 0.77 (m, 20 H); HRMS: m/z: found for C ₅₈ H ₆₆ S ₆ +: 954.34888.

2,2'-Bis[2-(4-octyl-4H-dithieno[3,2-b:2',3'-d]pyrroIe)]-3 ,3'-bithianaphtene (X)

Gravimetric chromatography using as eluent a hexane/CH ₂ C1 ₂ 8/2 mixture to give viscous orange oil which is repulped in methanol to give monomer X as an orange solid (yield: 27%); m.p.: 57-60°C; 1H NMR (300 MHz; acetone- d ₆ ): δ 7.99 (1H, d, J = 8.1 Hz), 7.38 (1H, s), 7.34 (1H, d, J= 7.8 Hz), 7.24 (1H, d, J= 7.8 Hz), 7.21 (1H, d, J= 5.1 Hz), 7.15 (1H, d, J= 7.8 Hz), 7.09 (1H, d, J= 5.7 Hz) 4.20 (2H, t, J= 6.9 Hz), 1.85 (2H, m), 1.24 (10H, m), 0.86 (3H, m); MS (EI+): m/z: 844.

2,2'-Bis(5,2',5',2"-terthiophen-2 _T yl)-3,3'-bithianaphtene (XII)

Gravimetric chromatography using as eluent a hexane/CH ₂ C1 ₂ 8/2 mixture to give monomer XII as yellow-orange solid (yield 35%); 1H NMR (300 MHz; CDC1 ₃ ): δ 7.96 (1H, d, J = 12.1), 7.42 (1H, t), 7.26 (4H, m), 7.18 (1H, d), 7.04 (3H, m), 6.92 (lH, d).

2,2'-Bis(thiophen-2-yl)-3,3'-bithianaphtene (XIII)

Gravimetric chromatography using as eluent a hexane/CH ₂ C1 ₂ 8/2 mixture to give monomer XIII as pale yellow solid (yield 75%); 1H NMR (300 MHz; CDC1 ₃ ): δ 8.06 (1H, d), 7.43 (1H, t), 7.26 (4H, m), 7.30 (3H, m), 7.16 (1H, d), 6.96 (1H, m).

3,3'-Bis(2,2'-bithiophen-5-yl)-N,N' -dimethyl-2,2'-bisindole (Villa)

2-iodobithiophene (4.46 g), K ₂ C0 ₃ (2.39 g) and Pd(PPh ₃ ) ₄ (0.28 mg) are added under inert atmosphere to a solution of o-alkynyltrifluoroacetanilide (1.47 g) ^[1] in CH ₃ CN (80 ml) at 80°C. The reaction mixture is kept under stirring for 8 hours under reflux, then water and AcOEt are added. The organic phase is separated, dried and the solvent is removed under reduced pressure to give a residue that is subjected to chromatography using as eluent a hexane: AcOEt 8:2 mixture. The final fractions are put together, the solvent is removed under reduced pressure to give 3,3-bis(2,2'- bithiophene-2-yl)-2,2'-bisindole (yield 47 %); 1H NMR (300 MHz; acetone-d ₆ ): δ 11.64 (1H, s), 7.46 (1H, d, J= 8.1 Hz), 7.42-7.34 (4H, m), 7.12 (1H, td, J= 8.0 Hz, J = 1.1 Hz), 6.92 (1H, d, J= 7.8 Hz), 6.85 (1H, td, J= 7.6 Hz, J= 3.8 Hz).

KOH (0.25 g) is added to a solution of 3,3-bis(2,2'-bithiophene-2-yl)-2,2'-bisindole (0.5 g) in DMF (7 ml) at 0 °C. The reaction mixture is left under stirring for 15 min, then methyl iodide (1.35 g) is added and the suspension left under stirring at room temperature for 48 hours. The mixture is diluted with H ₂ O (20 ml) and CH ₂ C1 ₂ (15 ml); the organic phase is separated, dried and the solvent removed under reduced pressure. The yellow fractions are put together, the solvent is removed under reduced pressure to give 3,3-bis(2,2'-bithiophen-2-yl)-N,N ^, -dimethyl-2,2'-bisindole (yield 67%); 1H NMR (300 MHz; acetone-d ₆ ): δ 8.15 ( 1H, d, J= 7.8 Hz), 7.61 (1H, d, J = 8.1 Hz), 7.39 (1H, t, J= 7.2 Hz), 7.34 (1H, d, J = 7.5 Hz), 7.31 (1H, d, J = 5.1 Hz), 7.11 (1H, d, J= 3.6 Hz), 7.06 (1H, d, J = 3.3 Hz), 6.98 (1H, d, J= 5.1 Hz), 6.95 (1H, d, J = 3.9 Hz), 3.60 (3H, s).

3,3'-Bis(2,2'-bithiophene-2-yl)-N,N'-dihexyl-2,2'-bisindole (VIIIb)

KOH (0.25 g) is added to a solution of 3,3-bis(2,2'-bithiophene-2-yl)-2,2'-bisindole (0.5 g) in DMF (7 ml) at 0 °C. The reaction mixture is left under stirring for 15 min, then 1-bromohexane (0.55 g) is added and the suspension left under stirring at room temperature for 48 hours. The mixture is diluted with H ₂ O (20 ml) and CH ₂ C1 ₂ (15 ml); the organic phase is separated, dried and the solvent removed under reduced pressure. The yellow fractions are put together, the solvent is removed under reduced pressure to give 3,3-bis(2,2'-bithiophene-2-yl)-N,N'-dihexyl-2,2'-bisindole (yield 67 %); 1H NMR (300 MHz; CD ₂ C1 ₂ ): δ 8.20 (1H, d, J = 7.8 Hz), 7.49 (1H, d, J = 8.1 Hz), 7.40 (1H, t, J= 6.6 Hz), 7.34 ((1H, t, J = 6.9 Hz), 7.19 (1H, d, J= 5.1 Hz), 7.06 (1H, d, J = 3.6 Hz), 7.04 (1H, d, J = 3.9 Hz), 6.98 (1H, dd, J = 5.1 Hz, J = 3.6 Hz), 6.88 (1H, d, J = 3.6 Hz), 3.85 (2H, m), 1.45 (2H, m), 1.11 (6H, m), 3.07 (3H, t, J = 3.6 Hz).

2,2'-Bis[4-(2,2'-bithiophen-5-yl)phenylene]-N,N' -dihexyl-3,3'-bisindole (VI)

2,2'-bis(4-bromophenylene)-N,N'-dihexyl-3,3'-bisindole (1.54 g) has been prepared by alkylation of 2,2'-bis(4-bromophenylene)-3,3'-bisindole ^[2] with 1-bromohexane in DMF according to the method described for monomer Vlllb.

5-(4,4,5,5-tetramethyl-l,3,2-dioxaborolan-2-yl)-2,2'-bithiop hene (1.78 g), Pd(PPh ₃ ) ₄ (0.38 g) and K ₂ CO ₃ (3 g) are added under inert atmosphere to a solution of 2,2'- bis(4-bromophenylene)-N,N-dihexyl-3,3'-bisindole (1.54 g) in THF (150 ml) and H ₂ O (15 ml). The reaction mixture is heated under reflux for 20 hours and the solvent is removed under reduced pressure. H ₂ O. (70 ml) and CH ₂ C1 ₂ (100 ml) are added to the residue; the organic phase is separated, dried and the solvent removed under reduced pressure. The residue is subjected to silica gel chromatography using as eluent a CH ₂ C1 ₂ /hexane 1/9 mixture. The yellow fractions are put together, the solvent is removed under reduced pressure to give monomer VI as yellow solid (75%); ¹ H NMR (300 MHz; acetone-d ₆ ): δ 7.56 (1H, d, J = 8.4 Hz), (1H, d, J= 8.4 Hz), 7.46 (5H, m), 7.35 (1H, d, J= 3.3 Hz), 7.31 (1H, d, J= 3.9 Hz), 7.25 (1H, t, 7.5 Hz), 7.12 (1H, dd, J= 5.1 Hz, J= 3.9 Hz), 7.07 (1H, d, J= 7.5 Hz), 6.88 (1H, d, J = 8.4 Hz).

^[1] A. Arcadi, S. Cacchi, G. Fabrizi, F. Marinelli, L.M. Parisi, J. Org. Chem. 2005, 70, 6213-6217.

[ ^2] T. Niu, Y. Zhang, Tetrahedron Lett. 2010, 51, 6847-6851.

General procedure for the preparation of macrocyclic oligothiophenes: A solution of the monomer (0.17 mmol) in anhydrous chloroform (50 ml) is added dropwise under inert atmosphere to a suspension of FeC1 ₃ (109 mg, 0.67 mmol) in anhydrous chloroform (150 ml), under vigorous stirring, at room temperature in 2 hours. The dark solution is kept under stirring for 12 hours, then the solvent volume is reduced to 100 ml by reduced pressure evaporation and the solution is poured into 150 ml MeOH. The precipitated solid was recovered by filtration, suspended in 30 ml MeOH and 4 drops of hydrazine hydrate are added to the suspension. The solid is recovered by filtration and extracted with THF, by using a Soxhlet apparatus. The solvent is left at reflux until it becomes colored. The solution, wherein the solvent has been removed under reduced pressure, gives a dark solid consisting of a mixture of cyclic oligomers, as demonstrated by LDI mass spectrometry (Laser Desorption Ionization).