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A series of 12H-[1]benzo[4′′,5′′]thieno[2′′,3′′:4′,5′]thieno[2′,3′:4,5]thieno[3,2-b]indoles were efficiently prepared in three steps starting from available benzo[b]thieno[2,3-d]thiophen-3(2H)-ones. These fused ketones were treated with the Vilsmeier reagent and hydroxylamine hydrochloride to give the corresponding 3-chlorobenzo[b]thieno[2,3-d]thiophene-2-carbonitriles, which then reacted with methyl sulfanylacetate to form methyl 3-aminobenzo[4′,5′]thieno[2′,3′:4,5]thieno[3,2-b]thiophene-2-carboxylates, in accordance with the Fiesselmann thiophene synthesis protocol. Finally, the desired N,S-heterohexacenes were obtained by conversion of these fused 3-aminothiophene-2-carboxylates into the corresponding 3-aminothiophene intermediates, which acted as synthetic equivalents of thiophen-3(2H)-ones, followed by their acid-promoted reaction with arylhydrazines, in accordance with the Fischer indolization procedure.

The effective approaches for regioselective double formylation and acetylation of 5,12-dialkyl-6,7-diaryl-substituted 5,12-dihydroindolo[3,2- a ]carbazoles by their treatment with dichloromethyl methyl ether in the presence of SnCl 4 or with acetyl chloride in the presence of AlCl 3 to afford the 2,9-diformyl or 2,9-diacetyl derivatives, respectively, were developed. Furthermore, new 2,9-bis(2,2-dicyanovinyl) derivatives were synthesized by the Knoevenagel condensation of diformyl-containing substrates with malononitrile, when new 2,9-bis(quinoxaline-2-yl)- and 2,9-bis(benzo[ g ]quinoxaline-2-yl) derivatives were formed via microwave-promoted oxidation of diacetyl-containing substrates with SeO 2 to the corresponding diglyoxals, followed by the reaction of these intermediates with o -phenylendiamine or 2,3-diaminonaphthalene, respectively. The basic optical and electrochemical properties of some 5,12-dihydroindolo[3,2- a ]carbazoles were investigated.

Two new classes of heteroacenes, namely benzo[4′,5′]thieno[2′,3′:4,5]thieno[3,2-b]quinolines and benzo[4′,5′]thieno[2′,3′:4,5]thieno[3,2-b][1,8]naphthyridines, have been formed using the Friedlander reaction to annulate the benzo[b]thieno[2,3-d]thiophene scaffold to quinoline or 1,8-naphthyridine fragments. In accordance with this synthetic strategy, benzo[b]thieno[2,3-d]thiophen-3(2H)-ones were treated with 2-aminobenzaldehydes or 2-aminonicotinaldehyde in the presence of pyrrolidine in glacial acetic acid at reflux to give the desired quinoline- or 1,8-naphthyridine-fused compounds, respectively. The optical and electrochemical properties of selected heteroacenes were determined.

A number of 5, 11-dialkyl-6, 12-di(hetero)aryl-5, 11-dyhydroindolo[3, 2-b]carbazoles has been synthesized by modified method based on HBr catalyzed condensation of (hetero)aromatic aldehydes with indole in MeCN solution affording 5, 6, 11, 12-tetrahydroindolo[3, 2-b]carbazoles, that have been aromatized with I2 in DMF solution for 1 h at reflux, followed by alkylation of 5, 11-dihydro compounds. New 2, 8-dicyano-(10 examples) as well as 2, 8-bis(benzo[d]thiazol-2-yl)-substituted (5 examples) derivatives of these 5, 11-dyhydroindolo[3, 2-b]carbazoles have been obtained through their initial C2, 8-formylation, followed by treatment of dialdehydes with excess of hydroxylamine and dehydration of the formed aldoximes with acetic anhydride or by interaction with excess of 2-aminothiophenol in DMSO solution, respectively. © 2018 Arkat. All rights reserved. This research study was supported financially by the Russian Science Foundation (Project No. 16-13-10435).

A new 5,11-dihydroindolo[3,2-b]carbazole-based bidentate ligand bearing two carboxylic groups, (3,3′-(indolo[3,2-b]carbazole-5,11-diyl)dipropionic acid, H2icdc), has been synthesized in two steps and then used for the construction of two metal–organic coordination polymers, namely [Zn3(dmf)2(icdc)3]·4DMF (1) and [Zn2(dabco)(icdc)2]·4NMP·4H2O (2) (dabco = 1,4-diazabicyclo[2.2.2]octane, DMF = N,N-dimethylformamide, NMP = N-methyl-2-pyrrolidone). Compound 1 has a layered structure, while compound 2 has a 3D framework structure. Both compounds display linker-based blue fluorescence.

A series of new 5,11-dihydroindolo[3,2-b]carbazole derivatives, containing functional thiophene, 2,2′-bithiophene or 2,2′:5′,2″-terthiophene moieties at both C-2 and C-8 positions of their fused scaffolds, have been obtained from 2,8-diacetyl-substituted 5,11-dihydroindolo[3,2-b]carbazole compounds through the effective strategy, which is based on the sequence of two reactions, namely the Vilsmeier–Haack formylation and the Fiesselmann thiophene synthesis. The starting acetyl substituted materials have been transformed into the corresponding 3-chlorocrylaldehyde-containing compounds by treatment with POCl3-DMF complex, followed by the reaction with alkyl thioglycolates or α-mercaptoacetone in the presence of triethylamine to afford 2-carboalkoxythiophene- or 2-acetylthiophene-linked derivatives. 2-Acetylthiophene derivatives have further been involved into the same sequence of reactions to obtain 2,2′-bithiophene-, and 2,2′:5′,2″-terthiophene-linked 5,11-dihydroindolo[3,2-b]carbazole compounds.

A new general approach to double nitration of 6,12-di(hetero)aryl-substituted and 6,12-unsubstituted 5,11-dialkyl-5,11-dihydroindolo[3,2-b]carbazoles by acetyl nitrate has been developed to obtain their 2,8-dinitro and 6,12-dinitro derivatives, respectively. A formation of mono-nitro derivatives (at C-2 or C-6) from the same indolo[3,2-b]carbazoles has also been observed in several cases. Reduction of 2-nitro and 2,8-dinitro derivatives with zinc powder and hydrochloric acid has afforded 2-amino- and 2,8-diamino-substituted indolo[3,2-b]carbazoles, while reduction of 6,12-dinitro derivatives under similar reaction conditions has been accompanied by denitrohydrogenation of the latter compounds into 6,12-unsubstituted indolo[3,2-b]carbazoles. Formylation of 6,12-dinitro derivatives has proved to occur only at C-2, while bromination of these compounds has taken place at both C-2 and C-8 of indolo[3,2-b]carbazole scaffold. Moreover, 6,12-dinitro-substituted indolo[3,2-b]carbazoles have been modified by the reactions with S- and N-nucleophiles. Notably, the treatment of 6,12-dinitro compounds with potassium thiolates has resulted in the displacement of both nitro groups, unlike potassium salts of indole or carbazole, which have caused substitution of only one nitro group.

New 3-(1 H -imidazol-2-yl)-9 H -carbazoles and 6,6′-di(1 H -imidazol-2-yl)-9 H ,9′ H -3,3′-bicarbazoles have been prepared, starting from 9-ethyl-9 H -carbazole-3-carbaldehyde or 9,9′-diethyl-9 H ,9′ H -[3,3′-bicarbazole]-6,6′-dicarbaldehyde through their reactions with 4-methoxyaniline or 4-fluoroaniline, benzil or 2,2′-thenil [1,2-di(thien-2,2′-yl) glyoxal] and ammonium acetate on reflux in glacial acetic acid. The obtained compounds have been shown to demonstrate an effective fluorescence in the blue spectral region, exhibiting quantum yields in the range of 0.08–0.51, depending on their molecular structure and solvent polarity. The nature of the observed absorption spectra has been elucidated by the TDDFT calculations.

Novel compounds—substituted indolo[3,2-b]carbazoles (SIC)—which demonstrate semiconducting properties are synthesized. Electroluminescence (EL) is studied in multilayer diode structures based on SIC. The values of hole (6.38 × 10–5 cm2/(V s)) and electron mobilities (1.31 × 10–5 cm2/(V s)) of these electroactive materials are measured. It is estimated that heteroaromatic nuclei are the electron transport centers of SIC molecules.

Fiesselmann thiophene synthesis was applied for the convenient construction of thieno[3,2-b]thiophene derivatives. Thus, new 5- or 6-aryl-3-hydroxythieno[3,2-b]thiophene-2-carboxylates were obtained by condensation of 5- or 4-aryl-3-chlorothiophene-2-carboxylates, respectively, with methyl thioglycolate in the presence of potassium tert-butoxide. The saponification of the resulting esters, with decarboxylation of the intermediating acids, gave the corresponding thieno[3,2-b]thiophen-3(2H)-ones. The latter ketones were used to synthesize new N,S-heterotetracenes, namely 9H-thieno[2',3':4,5]thieno[3,2-b]indoles by their treatment with arylhydrazines in accordance with the Fischer indolization reaction.

A series of new polycyclic compounds bearing the 5,11-dihydroindolo[3,2-b]carbazole ring system, as the common motif of their nine-ring scaffolds, has been successfully prepared with the usage of an efficient two-step strategy, based on the double Friedel–Crafts acylation of 5,11-dihexyl-6,12-di(hetero)aryl-substituted 5,11-dihydroindolo[3,2-b]carbazoles with 2-iodobenzoyl chloride in the presence of SnCl4, followed by regioselective palladium-catalyzed cyclization of the obtained 2,8-bis(2-iodobenzoyl) derivatives into the desired fused 9H-fluoren-9-ones. Some modifications of these nine-ring structures have been performed to afford compounds of the same family bearing the 9H-fluorene fragments. Basic photophysical and electrochemical properties as well as thermal stability of the new fused indolo[3,2-b]carbazole derivatives have been determined.

An efficient approach for the double acetylation of 5,11-dihexyl-6,12-di(hetero)aryl-substituted 5,11-dihydroindolo[3,2-b]carbazoles with acetic anhydride in the presence of boron trifluoride etherate has been developed, thus affording the corresponding 2,8-diacetyl derivatives in good yields. A similar acylation has been shown to occur by the reaction of anhydrides of other carboxylic acids. Oxidation of the obtained 2,8-diacetyl derivatives with selenium dioxide takes place on heating or under microwave irradiation, thus resulting in the formation of the corresponding 2,8-diglyoxals. The latter proved to react with aromatic o-diamines to afford new indolo[3,2-b]carbazoles bearing quinoxalinyl fragments at C-2 and C-8. Major optical properties of quinoxaline-containing indolo[3,2-b]carbazoles have been measured.

6-Styryl-5-(het)arylfurazano[3,4-b]pyrazines have been obtained by novel C–H functionalization, which is a particular case of the nucleophilic substitution of hydrogen (SNH). The process is initiated by the Michael addition of morpholine at the C C double bond of β-nitrostyrenes, and the subsequent addition of the generated carbanion to C-6 of 5-(het)arylfurazano[3,4-b]pyrazines, followed by elimination of nitrous acid and morpholine. It has been shown that in this case, only β-nitrostyrenes bearing electron-rich substituents on the aromatic ring are involved in arylalkenylation of furazano[3,4-b]pyrazines.

An automated installation based on National Instruments’ control and measurement equipment, vacuum chamber with resistive heater and “ThermoVac” virtual instrument was designed and tested for deposition of thin organic films by vacuum thermal evaporation method. A 5,11-dimethyl-5,11-dihydroindolo[3,2-b]carbazole layer with thickness of 200 ± 50 nm was applied on the surface of fused silica glass, titanium and titanium nitride substrates. Current-voltage characteristics of Ti/IC/Au and TiN/IC/Au/Ti films were studied. It was determined that deposited organic layer had p-type conductivity and charge carriers mobility of 4.9·10−7 cm2/(V.s).An automated installation based on National Instruments’ control and measurement equipment, vacuum chamber with resistive heater and “ThermoVac” virtual instrument was designed and tested for deposition of thin organic films by vacuum thermal evaporation method. A 5,11-dimethyl-5,11-dihydroindolo[3,2-b]carbazole layer with thickness of 200 ± 50 nm was applied on the surface of fused silica glass, titanium and titanium nitride substrates. Current-voltage characteristics of Ti/IC/Au and TiN/IC/Au/Ti films were studied. It was determined that deposited organic layer had p-type conductivity and charge carriers mobility of 4.9·10−7 cm2/(V.s).

An efficient approach for the double acetylation of 5,11-dihexyl-6,12-di(hetero)aryl-substituted 5,11-dihydroindolo[3,2-b]carbazoles with acetic anhydride in the presence of boron trifluoride etherate has been developed, thus affording the corresponding 2,8-diacetyl derivatives in good yields. A similar acylation has been shown to occur by the reaction of anhydrides of other carboxylic acids. Oxidation of the obtained 2,8-diacetyl derivatives with selenium dioxide takes place on heating or under microwave irradiation, thus resulting in the formation of the corresponding 2,8-diglyoxals. The latter proved to react with aromatic o-diamines to afford new indolo[3,2-b]carbazoles bearing quinoxalinyl fragments at C-2 and C-8. Major optical properties of quinoxaline-containing indolo[3,2-b]carbazoles have been measured.

Study of electron and hole mobility for 5,11-dihexyl-6,12-di(2-thienyl)indolo[3,2- b ]carbazoles has shown that their heteroaromatic cores act as electron transport centers.

The arylalkenylation reaction involves the Michael addition of morpholine to β-nitrostyrenes, addition of the resulting carbanion to substrates (II), and subsequent elimination of nitrous acid and morpholine.