A new synthetic approach to fused nine-ring systems of the indolo[3,2-b]carbazole family through double Pd-catalyzed intramolecular C–H arylation

Roman A. Irgashev*ab, Nikita A. Kazina, Grigory A. Kima, Gennady L. Rusinovab and Valery N. Charushinab
aPostovsky Institute of Organic Synthesis, Ural Division, Russian Academy of Sciences, S. Kovalevskoy Str. 22, Ekaterinburg 620990, Russia. E-mail: irgashev@ios.uran.ru; Fax: +7 343 369 30 58
bUral Federal University named after the First President of Russia B. N. Yeltsin, Mira Str. 19, Ekaterinburg 620002, Russia

Received 6th May 2016 , Accepted 11th July 2016

First published on 18th July 2016


Abstract

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.


Introduction

Polycyclic π-conjugated systems based on fused aromatic and heteroaromatic rings have gained considerable attention due to the wide application of these compounds in the development of photo- and electroactive organic materials for advanced electronic and optoelectronic devices.1,2 5,11-Dihydroindolo[3,2-b]carbazoles (indolo[3,2-b]carbazoles, ICZ) represent an important class of ladder-type N-heteroacenes, which have a large planar and rigid backbone. A great variety of ICZ derivatives have been stated previously as efficient hole-transporting, electroluminescent or sensitizing materials for organic light-emission diodes (OLEDs),3 organic field effect transistors (OFETs)4 and organic photovoltaics (OPVs),5 due to their excellent electrical and optical properties, and high resistance to photo-, thermal- and electrochemical degradation.6 Some indolo[3,2-b]carbazoles are also of high importance as biologically active compounds. Indeed, a number of their derivatives show an extremely strong affinity to the TCDD receptor (2,3,7,8-tetrachlorodibenzo-p-dioxine) (Ah-receptor),7 as well as they proved to possess a protective function against oxidative DNA damage.8 Furthermore, the first family of alkaloids based on ICZ scaffolds, namely malasseziazoles A–C, have recently been described in the literature, including isolation procedures, full structural characterization9 and their syntheses.10 Therefore, research studies of indolo[3,2-b]carbazoles, including elaboration of convenient and selective methods for construction and modification of their scaffolds appear to be an important subject, as confirmed by a growing interest in this topic during the past decades.11 At the same time, indenocarbazole 1 and bisindenocarbazole 2, which have the ICZ-like architecture, have also been stated as perspective subunits for organic electronics materials. Indeed, electroluminescent and luminescent properties of their derivatives, as well as charge carrier motilities proved to be at a good level.12 One can see, that compounds 1 and 2 involve simultaneously the structural fragments of fluorene and carbazole, and they have one or two common benzene rings, respectively (Fig. 1).
image file: c6ra11796a-f1.tif
Fig. 1 Structures of indenocarbazole 1 and bisindenocarbazole 2.

In this context, development of both efficient and effective routes to construct π-conjugated molecules, combining the overlapped fluorene and indolo[3,2-b]carbazole cores, is important for both pure organic chemistry and the structural design of new organic components for electronic devices. It should be noted that only a few examples of fused indolo[3,2-b]carbazoles bearing additional benzene rings at their basic skeletons, such as compounds 3–6, have so far been described in the literature (Fig. 2).13


image file: c6ra11796a-f2.tif
Fig. 2 Fused structures based on indolo[3,2-b]carbazole system.

Results and discussion

In the present paper we wish to report a convenient synthetic approach to a new class of fused polycyclic ICZ derivatives having nine rings in their ladder-type backbone. This approach is based on using regioselective intramolecular arylation through the palladium-catalyzed aromatic C–H bond functionalization, as the key process. The Pd-catalyzed reaction was used for one-step formation of two 9H-fluoren-9-one units from the corresponding 2-iodobenzophenone fragments, which were incorporated in the structure of the key precursors in order to obtain the target fused molecules. Notably, transition-metal-catalyzed cyclization or the Pschorr-type cyclization of benzophenone derivatives,14 radical cyclization of 2-arylbenzaldehydes15 as well as the Friedel–Crafts ring closures of 2-arylbenzoic acids and their derivatives16 are major synthetic strategies towards the construction of 9H-fluoren-9-ones bearing various substituents. At the same time, several procedures for the regioselective C2- and C8-functionalization of N,N′-dialkylated indolo[3,2-b]carbazoles, containing electron-rich (het)aromatic substituents at C-6 and C-12, have recently been described. In particular, formylation and benzoylation of these compounds with alkyl dichloromethyl esters (the Rieche formylation17) or benzoyl chloride, respectively, in the presence of SnCl4 as the Lewis acid have been reported,18a as well as their similar acetylation or propionylation with anhydrides of carboxylic acids in the presence of BF3 etherate.18b These synthetic data proved to be very useful for preparation of 2,8-bis(2-iodobenzoyl)-substituted ICZs, that were selected as key precursors for the synthesis of nine-ring structures according to our strategy. Thus, derivatives 8a–g have been synthesized in good yields by treatment of indolo[3,2-b]carbazoles 7a–g with 2-iodobenzoyl chloride in the presence of SnCl4 (Scheme 1, Table 1).
image file: c6ra11796a-s1.tif
Scheme 1 Preparation of 2,8-bis(2-iodobenzoyl)-substituted ICZs 8.
Table 1 Scope and yields of 2,8-bis(2-iodobenzoyl) derivatives 8
Entry ICZ 7 2,8-Bis(2-iodobenzoyl)-ICZ 8 (Het)Ar Yield (%) 8
1 7a 8a Ph 93
2 7b 8b image file: c6ra11796a-u1.tif 85
3 7c 8c image file: c6ra11796a-u2.tif 84
4 7d 8d image file: c6ra11796a-u3.tif 80
5 7e 8e image file: c6ra11796a-u4.tif 79
6 7f 8f image file: c6ra11796a-u5.tif 74
7 7g 8g image file: c6ra11796a-u6.tif 94


Compound 8a was chosen as a model to find optimal conditions for the selected Pd-catalyzed cyclization. Various amounts of palladium(II) acetate, used earlier for similar transformations as a catalyst, in the presence of mild bases, such as potassium acetate (KOAc) or potassium pivalate (KOPiv) in N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA) have been tested in this reaction (Scheme 2, Table 2).


image file: c6ra11796a-s2.tif
Scheme 2 Double Pd-catalyzed cyclization of compound 8a.
Table 2 Optimization of the reaction conditions for the double Pd-catalyzed cyclizationa
Entry Pd(OAc)2, mol% Base Solvent Yield (%) 9a
a Reaction conditions: 8a (0.5 mmol), Pd(OAc)2 (10–30 mol%), KOAc or KOPiv (3 mmol), DMF or DMA (8 ml) at 150 °C for 10 h under Ar atmosphere.b Tricyclohexylphosphine (PCy3) (40 mol%) was added.
1 20 KOAc DMF 30
2 20 KOPiv DMF 35
3 20 KOAc DMA Tracesb
4 20 KOAc DMA 68
5 10 KOAc DMA Mixture 8a/9a
6 30 KOAc DMA 69
7 20 KOPiv DMA 75


The target product 9a was obtained in 30–35% yields, when DMF was used as solvent for this cyclization (Table 2, entries 1 and 2). Due to the formation of a rather complicated mixture of by-products, which can hardly be separated and characterized, only moderate yields of 9a were reached in spite of a full conversion of the starting material 8a. The structural degradation of 8a has been assumed to occur under these cyclization conditions. Since the formed by-products have a very good solubility at ambient temperature in DMF, methanol, and in a mixture of DMF and methanol, while 9a is poorly soluble in these solvents; due to this fact, the latter was easily isolated and purified. It is worth noting that an addition of phosphine ligand (PCy3) has a dramatically adverse effect, since by-products are formed predominantly with a trace amount of the desired product (Table 2, entries 3). The yield of compound 9a can be enhanced significantly up to 68%, when DMA is used as the reaction solvent, instead of DMF (Table 2, entry 4), in the presence of catalytic amounts of Pd(OAc)2 (20 mol% proved to be necessary and sufficient). It has been demonstrated that the reaction proceeding with a reduced amount of Pd-catalyst (10 mol%) resulted in a poor conversion of the starting material 8a; on the other hand, yield of compound 9a has not been improved substantially when a larger amount of Pd-catalyst (30 mol%) (Table 2, entries 5 and 6) has been applied. It has also been found that the use of potassium pivalate as a base leads to a slightly increase of product yield, comparing to the related experiment with potassium acetate (Table 2, entries 7 and 4). Thus, these reaction conditions (Table 2, entry 7) have been selected as the most appropriate for the preparation of a series of compounds 9.

It is noteworthy that there are three possible options for double cyclization of compound 8a, thus corresponding to the formation of alternative structures 9a, 9a′ or 9a′′ (Fig. 3). The correct structure has been established on the basis of the 1H NMR data. First of all, unsymmetrical structure 9a′ has been excluded from the consideration, since it has a set of magnetically non-equivalent protons, and this structure doesn't correlates with a number of signals observed in the 1H NMR spectra of the synthesized product. In order to differentiate between two symmetrical structures 9a and 9a′′ one has to take into consideration the difference in positions of protons in tetra-substituted benzene rings C of these polycyclic systems (Fig. 3).


image file: c6ra11796a-f3.tif
Fig. 3 Possible structures of the cyclization product.

The ortho-oriented protons of the structure 9a′′ should be exhibited in the 1H NMR spectra as two doublets with a vicinal coupling constant of 7–9 Hz. Contrary to that, the structure 9a has two couples of para-oriented protons, the resonance signals of which are expected as singlets or doublets with a small coupling constant (Jpara < 1 Hz). Actually, the 1H NMR spectrum of the cyclization product in CDCl3 shows two characteristic singlets in the field of aromatic protons at 6.67 and 7.26 ppm, and this fact is in a full agreement with the structure 9a. Furthermore, unequivocal evidence for the structure 9a has been obtained by X-ray crystallography analysis, thus supporting the data of 1H and 13C NMR spectroscopy (Fig. 4).


image file: c6ra11796a-f4.tif
Fig. 4 X-ray single crystal structure of compound 9a. Thermal ellipsoids of 50% probability are presented.

In order to obtain a series of compounds 9, similar cyclization of 2,8-bis(2-iodobenzoyl)-ICZ precursors 8b–g, bearing (hetero)aromatic substituents at C-6 and C-12, have been studied under the optimized reaction conditions for the synthesis of product 9a (Scheme 3, Table 3). The reaction proved to proceed in the same regioselective manner to give the target ICZ-cored compounds 9b–e in good yields. However, all attempts to cause cyclization of 8f,g with thien-2-yl or 4-bromophenyl substituents at C-6 and C-12 have failed, affording rather complicated mixtures of unidentified products. It can possibly be associated with concurrent Pd-catalyzed processes, such as the direct C–H arylation of α-unsubstituted thein-2-yl moieties19 of 8f or undesirable oxidative addition of palladium to C–Br bonds of 4-bromophenyl moieties of 8g. It is worth noting that the cyclization of 8e bearing the α-protected thien-2-yl substituents at C-6 and C-12, namely 5-methylthien-2-yl fragments, proved to proceed normally (contrary to 8f), thus affording the desired product 9e.


image file: c6ra11796a-s3.tif
Scheme 3 Synthesis of fused ICZ-cored compounds 9.
Table 3 Scope and yields of fused ICZ-cored compounds 9
Entry Key precursor 8 (Het)Ar ICZ-cored product 9 Yield (%) 9
a A complex mixture of compounds appears to be formed.
1 8a Ph 9a 75
2 8b image file: c6ra11796a-u7.tif 9b 80
3 8c image file: c6ra11796a-u8.tif 9c 77
4 8d image file: c6ra11796a-u9.tif 9d 95
5 8e image file: c6ra11796a-u10.tif 9e 76
6 8f image file: c6ra11796a-u11.tif Not obtaineda
7 8g image file: c6ra11796a-u12.tif Not obtaineda


In addition, a full reduction of two oxo groups in both 9H-fluoren-9-one fragments of polycyclic compounds 9 has been carried out in order to demonstrate an opportunity of their further modification into scaffolds bearing fused fluorene parts. It has been found that compounds 9a,e can be transformed into the corresponding products 10a,e on treatment with an excess of AlH3 (generated in situ from AlCl3 and LiAlH4) in dry THF solution (Scheme 4). It should be noted that all attempts to synthesize compounds 10 under other reaction conditions, such as that treatment with Et3SiH in solution of trifluoroacetic acid20 or use of hydrazine hydrate and potassium hydroxide in solution of ethylene glycol (the Wolff–Kishner reduction),21 proved to be unsuccessful. It is interesting to note that compounds 10 are oxidized slowly by air oxygen back into the starting materials 9 (according to TLC) during their storage in solutions (e.g. THF, CHCl3), and this process is accelerated by the presence of a base. Also partly reduced compounds 10a,e have been methylated on treatment of their solutions in dry THF with an excess of iodomethane and potassium tert-butoxide under inert argon atmosphere, thus affording the corresponding tetramethyl-substituted derivatives 11a,e (Scheme 4).


image file: c6ra11796a-s4.tif
Scheme 4 Successive reduction and methylation of compounds 9a,e.

The UV-visible absorption and photoluminescence spectra of ICZ-cored compounds 9a–e and 11a,e were recorded at ambient temperature in CH2Cl2 solution (2 × 10−5 mol L−1), and the obtained results are summarized in Table 4 and Fig. 5 (also see ESI, S35–S38). Derivatives 9a–d exhibited very similar absorption spectra with maxima at 373–374 nm (Fig. 5a). The absorption maximum of derivative 9e slightly red-shifted to 378 nm. The solutions of all compounds 9a–e have small orange luminescence with emission maxima at 562–578 nm (Table 4, Fig. 5b); thus, relative quantum yields varies from 4.4% to 4.7%. The absorption maxima of derivatives 11a and 11e are 388 nm and 395 nm, respectively (Fig. 5a). The solutions of these ICZs have high blue luminescence with emission maxima at 464–467 nm and the second maxima at 493–497 nm; relative quantum yields are 40.6% (11a) and 26.3% (11e). The optical band gaps (Eoptg) of fused ICZs 9a–e and 11a,e were estimated from the onset of the long-wavelength absorption band of their UV-spectra, and these data are also summarized in Table 4.

Table 4 The optical, electrochemical and thermal properties of ICZ-cored compounds 9a–e and 11a,e
Compound absλmax (nm) emλmax (nm) Eonsetox (V) EHOMO (eV) ELUMO (eV) Eoptg (eV) Φa (%) Tdb (°C)
a Quantum yields (Φ) were estimated with 0.05 mol L−1 H2SO4 solution of quinine sulfate as a reference.b Decomposition temperatures (Td) were determined by TGA at weight loss of 5%.
9a 373 573 0.67 –5.55 –3.02 2.53 4.7 468
9b 374 578 0.64 –5.52 –3.01 2.51 4.6 467
9c 373 564 0.70 –5.58 –3.03 2.55 4.5 449
9d 373 575 0.63 –5.51 –3.00 2.51 4.4 468
9e 378 562 0.71 –5.59 –3.03 2.56 4.6 448
11a 388 464 0.33 –5.21 –2.52 2.69 40.6 441
11e 394 467 0.39 –5.27 –2.61 2.66 27.3 432



image file: c6ra11796a-f5.tif
Fig. 5 The UV-vis. absorption (a) and photoluminescence (b) spectra of ICZs 9a–e and 11a,e.

Cyclic voltammetry (CV) measurements of fused ICZs 9a–e and 11a,e were performed to study their electrochemical properties. All these CV experiments were carried out in a three electrode cell using the Ag/AgNO3 as the reference electrode under an argon atmosphere at a scan rate of 100 mV s−1 with the concentration of 1 × 10−3 mol L−1 for the examined substances in dry CH2Cl2 solution of n-Bu4NBF4 (0.1 M) that was used as the background electrolyte. It was found that derivatives 9a–e showed two oxidation waves, while derivatives 11a,e showed three oxidation waves according to the results of CV analysis (also see ESI, S39–S42). At the same time, reduction potentials were out of scan range in current CV experiments, that indicating a low electron affinity of the investigated compounds due to strongly electron-rich character of their ICZ frameworks. The HOMO energy levels (EHOMO) of these ICZs were estimated from the onset potentials (Eonsetox) of the first oxidation peaks by the empirical equation: EHOMO (eV) = − [EonsetoxE1/2(Fc/Fc+) + 5.1] under the premise that the formal potential of the Fc/Fc+ redox couple is −5.10 eV in the Fermi scale instead of −4.8 V for 0.0 V vs. Fc/Fc+ in accordance with a recent discussion of Bazan et al.22 The half-wave potential (E1/2) of ferrocene/ferrocenium (Fc/Fc+) redox couple was found experimentally at 0.22 V vs. Ag/Ag+ electrode for calibration purpose. The LUMO energy levels (ELUMO) of these compounds were calculated from their HOMO energy levels (EHOMO) and the optical band gaps (Eoptg) using equation: ELUMO = EHOMO + Eoptg. The obtained electrochemical data as well as the HOMO/LUMO energy levels are listed in Table 4.

Moreover, the thermal stability of ICZ-cored compounds 9a–e and 11a,e were examined by thermogravimetric analysis (TGA) at a scanning rate of 10 °C min−1 under an argon atmosphere, and the obtained data are summarized in Table 4 (also see ESI, S43–S46). Thus, all of these substances exhibited a very high thermal resistance, which is important for most optoelectronic applications, and the values of their decomposition temperatures (Td), defined as the temperature at which the sample showed a 5% weight loss, far exceed 400 °C. Foremost, it can be attributed to rigid and planar structure of the investigated compounds having nine-ring scaffolds. Furthermore, these results are also in a good agreement with the previous reports of high thermal stability of ICZ derivatives.6c

Conclusions

In conclusion it is worth mentioning that we have succeeded to develop a convenient synthetic route to a new family of indolo[3,2-b]carbazoles having a rigid planar nine-ring skeleton with ladder-type structure. Also further modifications of these scaffolds have been demonstrated. Additionally, physicochemical measurements have been performed for a series of the obtained nine-ring ICZ-cored compounds to estimate their optical and redox properties as well as thermal stability. Generally, the target compounds have been synthesized in good yields through regioselective palladium-catalyzed double cyclization of 2,8-bis(2-iodobenzoyl)-substituted indolo[3,2-b]-carbazoles, containing n-hexyl chains at both nitrogen atoms and (hetero)aromatic substituents at C-6 and C-12. These cyclization have been carried out successfully using palladium(II) acetate (catalyst) in the presence of an excess of potassium pivalate (base), but without any other additives or ligands. In summary, the synthetic strategy for construction of polycyclic scaffolds and their modifications reported herein are important for the design of new π-extended structures for ICZ-based materials, as well as for their further plausible applications in organic electronics and photovoltaics.

Experimental

General information

1H and 13C NMR spectra were obtained on a Bruker DRX-400 and AVANCE-500 spectrometers with TMS as internal standard. The 13C NMR spectrum of compound 8b was not recorded because of poor solubility of this substance in a majority of deuterated solvents. The starting materials 7 were prepared in accordance with the previously described procedures,18 new compound 7e is characterized below. Elemental analysis was carried on a Eurovector EA 3000 automated analyzer. Mass spectrometry was performed using a Bruker maXis Impact HD spectrometer. Melting points were determined on Boetius combined heating stages and were not corrected. All solvents used were dried and distilled per standard procedures. IR spectra of samples (solid powders) were recorded on a Spectrum One Fourier transform IR spectrometer (Perkin Elmer) equipped with a diffuse reflectance attachment (DRA). X-ray diffraction analysis was performed on an automated X-ray diffractometer “Xcalibur E” on standard procedure. UV-visible spectra were recorded for a 2 × 10−5 M dichloromethane solution with Shimadzu UV-2401PC spectrophotometer. Photoluminescence spectra were recorded for a 2 × 10−5 M dichloromethane solution on a Varian Cary Eclipse fluorescence spectrophotometer. Cyclic voltammetry (CV) measurements were performed on a Autolab PGSTAT128N potentiostat/galvanostat at ambient temperature. Thermogravimetric analysis (TGA) was carried out using Mettler Toledo DSC/TGA 1 system in argon atmosphere at a flow rate of 30 ml min−1, with a heating rate of 10 °C min−1.
5,11-Dihexyl-6,12-bis(5-methylthiophen-2-yl)-5,11-dihydroindolo[3,2-b]carbazole (7e). Yield 81%, light yellow needles, mp 208–209 °C; IR (DRA): ν = 3047, 2926, 2853, 1681, 1607, 1517, 1475, 1387, 1366, 1347, 1322, 1285, 1229, 1158, 1129, 1090, 1028, 993, 958, 922, 794, 740, 602, 551 cm−1; 1H NMR (400 MHz, CDCl3): δ = 7.41–7.35 (m, 2H), 7.31 (d, J = 8.1 Hz, 2H), 7.07 (d, J = 3.2 Hz, 2H), 6.99–6.93 (m, 4H), 6.87 (d, J = 7.7 Hz, 2H), 4.11–3.93 (m, 4H), 2.69 (s, 6H), 1.72–1.61 (m, 4H), 1.32–1.16 (m, 8H), 1.16–1.07 (m, 4H), 0.88 (t, J = 7.1 Hz, 6H); 13C NMR (126 MHz, CDCl3): δ = 142.4, 141.5, 136.5, 133.7, 128.1, 125.6, 125.5, 124.0, 122.6, 122.5, 118.3, 110.9, 108.4, 44.5, 31.5, 29.1, 26.7, 22.7, 15.6, 14.0; anal. calcd for C40H44N2S2: C, 77.88; H, 7.19; N, 4.54. Found: C, 77.49; H, 7.33; N, 4.99.

General procedure for the preparation of 2,8-bis(2-iodobenzoyl)-substituted 5,11-dihexyl-6,12-di(hetero)aryl-5,11-dihydroindolo[3,2-b]carbazoles (8a–g)

SnCl4 (790 mg, 3 mmol) was added dropwise to the solution of appropriate indolo[3,2-b]carbazole 7 (1 mmol) and 2-iodobenzoyl chloride (800 mg, 3 mmol) in dry CH2Cl2 (25 ml) at 0–5 °C, and the resulting mixture was stirred at room temperature for 12 h. The dark-green reaction mixture was then poured onto ice water (100 ml) and vigorously stirred for 1 h. The organic layer was separated and washed one time with water (50 ml), then with a 5% solution of NaOH (20 ml) and dried with MgSO4. The CH2Cl2 extract was concentrated under vacuum and the residue was suspended in hot EtOH (20 ml) at good shaking. This suspension was filtered and crude product 8 was purified by crystallization from DMF (20–25 ml). The analytically pure form of product 8 was separated by filtration, washed with EtOH (4 × 5 ml) and dried at 120 °C.
(5,11-Dihexyl-6,12-diphenyl-5,11-dihydroindolo[3,2-b]carbazole-2,8-diyl)bis((2-iodophenyl)methanone) (8a). Yield 93%, light yellow powder, mp 330–331 °C; IR (DRA): ν = 3062, 2931, 2854, 1651, 1602, 1565, 1524, 1463, 1444, 1382, 1351, 1311, 1275, 1252, 1172, 1141, 1082, 1059, 1015, 963, 921, 820, 765, 743, 728, 702, 670, 633 cm−1; 1H NMR (400 MHz, CDCl3): δ = 8.18 (dd, J = 8.7, 1.6 Hz, 2H), 7.90 (d, J = 7.9 Hz, 2H), 7.51–7.44 (m, 4H), 7.43–7.38 (m, 2H), 7.36–7.27 (m, 6H), 7.25–7.21 (m, 2H), 7.19–7.14 (m, 2H), 7.07 (dd, J = 7.5, 1.4 Hz, 2H), 6.66 (d, J = 1.4 Hz, 2H), 3.88–3.69 (m, 4H), 1.54–1.44 (m, 4H), 1.25–1.15 (m, 4H), 1.13–1.03 (m, 4H), 0.93–0.75 (m, 10H); 13C NMR (126 MHz, CDCl3): δ = 196.5, 145.4, 145.0, 138.9, 136.5, 132.6, 129.8, 129.0, 128.3, 128.0, 127.8, 127.5, 127.2, 126.6, 125.8, 122.7, 121.6, 118.5, 108.5, 91.9, 44.2, 30.9, 28.4, 25.8, 22.0, 13.5; anal. calcd for C56H50N2O2I2: C, 64.87; H, 4.86; N, 2.70. Found: C, 64.66; H, 4.66; N, 2.74; HRMS (+ESI): calcd for C56H51I2N2O2 m/z 1037.2035 [M + H]+, found m/z 1037.2022 [M + H]+.
(5,11-Dihexyl-6,12-bis(4-methoxyphenyl)-5,11-dihydroindolo[3,2-b]carbazole-2,8-diyl)bis((2-iodophenyl)methanone) (8b). Yield 85%, yellow needles, mp 309–310 °C; IR (DRA): ν = 3073, 2949, 2922, 2854, 1650, 1601, 1566, 1531, 1502, 1468, 1382, 1352, 1332, 1314, 1278, 1252, 1175, 1145, 1080, 1028, 1016, 962, 839, 822, 777, 767, 746, 725, 633 cm−1; 1H NMR (500 MHz, CDCl3): δ = 8.19 (dd, J = 8.7, 1.7 Hz, 2H), 7.87 (d, J = 7.3 Hz, 2H), 7.41–7.31 (m, 8H), 7.19 (td, J = 7.8, 1.7 Hz, 2H), 7.08 (dd, J = 7.5, 1.5 Hz, 2H), 6.98 (d, J = 1.5 Hz, 2H), 6.85 (d, J = 8.6 Hz, 4H), 3.90 (s, 6H), 3.77–3.72 (m, 4H), 1.52–1.43 (m, 4H), 1.26–1.18 (m, 4H), 1.15–1.06 (m, 4H), 0.94–0.88 (m, 4H), 0.85 (t, J = 7.3 Hz, 6H); anal. calcd for C58H54N2O4I2: C, 63.51; H, 4.96; N, 2.55. Found: C, 63.36; H, 5.00; N, 2.18.
(6,12-Bis(4-fluorophenyl)-5,11-dihexyl-5,11-dihydroindolo[3,2-b]carbazole-2,8-diyl)bis((2-iodophenyl)methanone) (8c). Yield 84%, light yellow crystals, mp 348–350 °C; IR (DRA): ν = 3068, 2953, 2930, 2855, 1659, 1603, 1566, 1528, 1499, 1467, 1381, 1353, 1312, 1276, 1251, 1222, 1157, 1142, 1082, 1015, 964, 835, 823, 779, 762, 744, 729, 657, 634 cm−1; 1H NMR (500 MHz, CDCl3): δ = 8.25 (dd, J = 8.7, 1.7 Hz, 2H), 7.90 (d, J = 7.8 Hz, 2H), 7.45–7.40 (m, 6H), 7.37 (d, J = 8.8 Hz, 2H), 7.30–7.27 (m, 2H), 7.08 (dd, J = 7.5, 1.6 Hz, 2H), 7.04–6.99 (m, 4H), 6.80 (d, J = 1.5 Hz, 2H), 3.76–3.70 (m, 4H), 1.52–1.43 (m, 4H), 1.26–1.18 (m, 4H), 1.14–1.07 (m, 4H), 0.94–0.88 (m, 4H), 0.86 (t, J = 7.3 Hz, 6H); 13C NMR (126 MHz, CDCl3): δ = 196.9, 162.5 (d, JCF = 249.4 Hz), 145.6, 145.4, 139.4, 133.4, 132.9 (d, JCF = 3.2 Hz), 131.3 (d, JCF = 7.6 Hz), 130.8, 128.3, 127.74, 127.65, 127.1, 126.4, 123.2, 122.0, 118.0, 116.2 (d, JCF = 21.0 Hz), 109.2, 92.1, 44.8, 31.4, 28.9, 26.4, 22.5, 13.9; anal. calcd for C56H48N2O2F2I2: C, 62.70; H, 4.51; N, 2.61. Found: C, 62.49; H, 4.50; N, 2.40.
(5,11-Dihexyl-6,12-bis(4-isopropylphenyl)-5,11-dihydroindolo[3,2-b]carbazole-2,8-diyl)bis((2-iodophenyl)methanone) (8d). Yield 80%, light yellow powder, mp 264–265 °C; IR (DRA): ν = 3064, 2929, 2866, 1654, 1565, 1532, 1499, 1461, 1381, 1351, 1331, 1311, 1277, 1253, 1170, 1142, 1082, 1016, 964, 830, 776, 764, 744, 724, 673, 655, 633 cm−1; 1H NMR (400 MHz, CDCl3): δ = 7.90 (dd, J = 8.7, 1.5 Hz, 2H), 7.87 (d, J = 8.1 Hz, 2H), 7.47 (d, J = 8.0 Hz, 4H), 7.40–7.27 (m, 8H), 7.21 (d, J = 1.4 Hz, 2H), 7.17–7.11 (m, 4H), 3.77–3.64 (m, 4H), 3.09–2.97 (m, 2H), 1.56–1.44 (m, 4H), 1.39 (d, J = 6.9 Hz, 12H), 1.26–1.17 (m, 4H), 1.17–1.09 (m, 4H), 0.91–0.79 (m, 10H); 13C NMR (126 MHz, CDCl3): δ = 196.0, 148.7, 145.1, 145.0, 138.9, 133.8, 133.1, 130.0, 129.1, 128.1, 127.8, 127.0, 126.5, 126.5, 125.8, 122.6, 122.2, 118.7, 107.8, 92.2, 44.3, 33.1, 31.0, 28.4, 25.8, 23.6, 22.1, 13.6; HRMS (+ESI): calcd for C62H62I2N2O2 m/z 1120.2895 [M], found m/z 1120.2899 [M].
(5,11-Dihexyl-6,12-bis(5-methylthiophen-2-yl)-5,11-dihydroindolo[3,2-b]carbazole-2,8-diyl)bis((2-iodophenyl)methanone) (8e). Yield 79%, light yellow needles, mp 301–302 °C; IR (DRA): ν = 3070, 2952, 2924, 2858, 1650, 1601, 1565, 1516, 1447, 1427, 1386, 1350, 1315, 1254, 1158, 1139, 1079, 1049, 1016, 960, 934, 905, 794, 775, 742, 725, 676, 656, 634 cm−1; 1H NMR (400 MHz, CDCl3): δ = 8.23 (dd, J = 8.7, 1.5 Hz, 2H), 7.94 (d, J = 8.0 Hz, 2H), 7.44 (td, J = 7.5, 0.9 Hz, 2H), 7.40 (d, J = 8.8 Hz, 2H), 7.25–7.18 (m, 4H), 7.14–7.12 (m, 2H), 6.91 (d, J = 3.2 Hz, 2H), 6.49 (d, J = 3.1 Hz, 2H), 4.11–3.88 (m, 4H), 2.47 (s, 6H), 1.70–1.59 (m, 4H), 1.29–1.23 (m, 4H), 1.22–1.14 (m, 4H), 1.12–1.03 (m, 4H), 0.88 (t, J = 7.1 Hz, 6H); 13C NMR (101 MHz, CDCl3): δ = 197.0, 145.9, 145.5, 141.6, 139.3, 134.6, 134.5, 130.3, 129.0, 128.4, 128.3, 127.6, 127.4, 126.6, 125.5, 124.5, 121.8, 112.1, 109.2, 92.5, 44.8, 31.4, 29.4, 26.6, 22.6, 16.0, 14.0; anal. calcd for C54H50I2N2S2O2: C, 60.22; H, 4.68; N, 2.60. Found: C, 60.29; H, 4.91; N, 2.71; HRMS (+ESI): calcd for C54H51I2N2O2S2 m/z 1077.1476 [M + H]+, found m/z 1077.1458 [M + H]+.
(5,11-Dihexyl-6,12-di(thiophen-2-yl)-5,11-dihydroindolo[3,2-b]carbazole-2,8-diyl)bis((2-iodophenyl)methanone) (8f). Yield 74%, yellow crystals, mp 313–314 °C; IR (DRA): ν = 3073, 2929, 2855, 1650, 1602, 1567, 1500, 1462, 1430, 1390, 1357, 1343, 1308, 1275, 1250, 1161, 1143, 1080, 1015, 961, 917, 820, 765, 743, 726, 696, 670, 657, 633 cm−1; 1H NMR (500 MHz, CDCl3): δ = 8.23 (dd, J = 8.7, 1.4 Hz, 2H), 7.93 (d, J = 7.9 Hz, 2H), 7.49–7.43 (m, 2H), 7.40 (d, J = 8.8 Hz, 2H), 7.27–7.23 (m, 2H), 7.19–7.15 (m, 4H), 7.13–7.11 (m, 2H), 6.86 (dd, J = 5.1, 3.5 Hz, 2H), 6.73 (s, 2H), 4.06–3.86 (m, 4H), 1.69–1.57 (m, 4H), 1.31–1.20 (m, 4H), 1.20–1.12 (m, 4H), 1.09–0.97 (m, 4H), 0.87 (t, J = 7.2 Hz, 6H); 13C NMR (126 MHz, CDCl3): δ = 197.0, 146.0, 145.4, 139.3, 136.7, 134.3, 130.2, 128.4, 128.1, 127.9, 127.9, 127.4, 127.3, 127.1, 126.6, 124.7, 121.6, 111.7, 109.2, 92.5, 44.8, 31.4, 29.3, 26.5, 22.5, 14.0; anal. calcd for C52H46N2S2I2O2: C, 59.55; H, 4.42; N, 2.67. Found: C, 59.47; H, 4.51; N, 2.69.
(6,12-Bis(4-bromophenyl)-5,11-dihexyl-5,11-dihydroindolo[3,2-b]carbazole-2,8-diyl)bis((2-iodophenyl)methanone) (8g). Yield 94%, yellow crystals, mp > 370 °C; IR (DRA): ν = 3061, 2955, 2928, 2856, 1644, 1603, 1566, 1522, 1447, 1383, 1350, 1332, 1312, 1275, 1249, 1169, 1141, 1082, 1071, 1011, 964, 825, 761, 742, 678, 654, 633 cm−1; 1H NMR (500 MHz, CDCl3): δ = 8.22 (dd, J = 8.7, 1.6 Hz, 2H), 7.97 (d, J = 8.0 Hz, 2H), 7.49 (d, J = 8.2 Hz, 4H), 7.43 (t, J = 7.5 Hz, 2H), 7.39–7.31 (m, 8H), 7.11–7.06 (m, 4H), 3.67–3.62 (m, 4H), 1.49–1.40 (m, 4H), 1.27–1.21 (m, 4H), 1.15–1.08 (m, 4H), 0.98–0.85 (m, 10H); 13C NMR (126 MHz, CDCl3): δ = 196.9, 145.6, 145.1, 139.6, 135.9, 133.4, 132.1, 131.5, 131.2, 128.0, 127.9, 127.7, 127.3, 126.5, 122.9, 122.6, 121.8, 117.8, 109.2, 92.1, 44.9, 31.4, 29.0, 26.4, 22.6, 14.0; anal. calcd for C56H48N2Br2I2O2: C, 56.30; H, 4.05; N, 2.34. Found: C, 56.22; H, 4.00; N, 2.56.

General procedure for the preparation of fused ICZ-based compounds (9a–e) via double Pd-catalyzed cyclization of 2,8-bis(2-iodobenzoyl) derivatives (8a–e)

Appropriate compound 8 (0.5 mmol), Pd(OAc)2 (23 mg, 0.1 mmol) and potassium pivalate (420 mg, 3 mmol) together with dry DMA (8 ml) were placed in a 25 ml Schlenk tube equipped with a magnetic stir bar. The suspension was degassed by several cycles (4–5 times) of vacuum pumping and flushing with dry argon and then heated with stirring under an argon atmosphere at 150 °C for 10 h. The opaque mixture was slightly cooled and diluted with MeOH (8 ml) to obtain dark-orange precipitate of the crude product which was isolated by filtration. This precipitate was treated with hot CHCl3 (20 ml) and filtered to remove palladium metal which additionally washed with hot CHCl3 (10 ml) on a filter. The CHCl3 solution was evaporated under reduced pressure and the orange residue was recrystallized for DMF or DMA (15 ml). The analytically pure product 9 was filtered, washed with EtOH (2 × 5 ml) and then dried at 120 °C.
6,15-Dihexyl-7,16-diphenyl-6,15-dihydroindeno[1,2-b]indeno[2′,1′:5,6]indolo[2,3-h]carbazole-9,18-dione (9a). Yield 75%, orange crystals, mp > 370 °C; IR (DRA): ν = 3067, 2952, 2929, 2855, 1691, 1608, 1521, 1471, 1405, 1347, 1290, 1256, 1230, 1189, 1155, 1092, 1073, 1052, 1020, 985, 881, 809, 759, 742, 726, 702, 623 cm−1; 1H NMR (500 MHz, CDCl3): δ = 7.77–7.73 (m, 2H), 7.72–7.68 (m, 4H), 7.67–7.63 (m, 4H), 7.57–7.53 (m, 4H), 7.41 (td, J = 7.5, 1.0 Hz, 2H), 7.26 (s, 2H), 7.22 (td, J = 7.4, 0.7 Hz, 2H), 6.67 (s, 2H), 3.95–3.72 (m, 4H), 1.58 (dd, J = 23.7, 8.5 Hz, 4H), 1.29–1.21 (m, 4H), 1.19–1.11 (m, 4H), 0.97–0.90 (m, 4H), 0.88 (t, J = 7.3 Hz, 6H); 13C NMR (101 MHz, CDCl3): δ = 192.5, 146.7, 144.4, 142.3, 137.3, 136.7, 133.8, 133.6, 130.0, 129.6, 129.0, 128.7, 125.8, 123.8, 123.5, 123.0, 120.0, 119.9, 118.9, 100.5, 44.8, 31.4, 29.0, 26.3, 22.6, 14.0; HRMS (+ESI): calcd for C56H49N2O2 m/z 781.3789 [M + H]+, found m/z 781.3799 [M + H]+.
Crystal data for compound 9a (C56H48N2O2). Crystal is monoclinic, space group P21/c, a = 10.9788(8) Å, b = 25.286(3) Å, c = 16.0994(7) Å, α = 90.00°, β = 100.188(6)°, γ = 90.00°, U = 4398.9(6) Å3, Z = 4, T = 295(2) K, absorption coefficient 0.071 mm−1, reflections collected 19797, independent reflections 8977 [R(int) = 0.0431], refinement by full-matrix least-squares on F2, data/restraints/parameters 8977/142/642, goodness-of-fit on F2 = 1.037, final R indices [I > 2σ(I)] R1 = 0.0680, wR2 = 0.1632, R indices (all data) R1 = 0.1733, wR2 = 0.2204, largest diff peak and hole 0.297 and −0.184 e Å−3.

Deposition number CCDC 1478325 contains the supplementary crystallographic data for this structure.

6,15-Dihexyl-7,16-bis(4-methoxyphenyl)-6,15-dihydroindeno[1,2-b]indeno[2′,1′:5,6]indolo[2,3-h]carbazole-9,18-dione (9b). Yield 80%, orange needles, mp > 370 °C; IR (DRA): ν = 3069, 2955, 2930, 2851, 1702, 1609, 1529, 1504, 1466, 1445, 1404, 1346, 1306, 1287, 1245, 1178, 1154, 1092, 1026, 984, 917, 846, 834, 815, 765, 726, 621 cm−1; 1H NMR (400 MHz, CDCl3): δ = 7.61–7.50 (m, 8H), 7.45–7.39 (m, 2H), 7.27 (s, 2H), 7.25–7.20 (m, 6H), 6.83 (s, 2H), 4.04 (s, 6H), 3.98–3.80 (m, 4H), 1.63–1.53 (m, 4H), 1.32–1.21 (m, 4H), 1.16 (dt, J = 14.0, 6.8 Hz, 4H), 1.05–0.95 (m, 4H), 0.88 (t, J = 7.2 Hz, 6H); 13C NMR (126 MHz, CDCl3) δ 192.5, 160.2, 146.7, 144.4, 142.2, 136.7, 134.0, 133.0, 131.0, 129.1, 128.7, 125.7, 124.2, 123.5, 123.1, 120.1, 119.8, 118.6, 115.0, 100.5, 55.7, 44.7, 31.4, 29.0, 26.4, 22.6, 14.0; anal. calcd for C58H52N2O4: C, 82.83; H, 6.23; N, 3.33. Found: C, 82.61; H, 5.99; N, 3.34.
7,16-Bis(4-fluorophenyl)-6,15-dihexyl-6,15-dihydroindeno[1,2-b]indeno[2′,1′:5,6]indolo[2,3-h]carbazole-9,18-dione (9c). Yield 77%, orange crystals, mp 339–340 °C; IR (DRA): ν = 3065, 2957, 2932, 2858, 1697, 1607, 1525, 1499, 1471, 1404, 1345, 1289, 1245, 1225, 1187, 1153, 1092, 1074, 1050, 1017, 985, 913, 849, 765, 758, 726, 622 cm−1; 1H NMR (500 MHz, CDCl3): δ = 7.65–7.60 (m, 4H), 7.59–7.54 (m, 4H), 7.46–7.39 (m, 6H), 7.28 (s, 2H), 7.25–7.22 (m, 2H), 6.78 (s, 2H), 3.88–3.79 (m, 4H), 1.62–1.53 (m, 4H), 1.32–1.23 (m, 4H), 1.21–1.13 (m, 4H), 1.03–0.96 (m, 4H), 0.89 (t, J = 7.3 Hz, 6H); 13C NMR (101 MHz, CDCl3): δ = 192.4, 163.2 (d, JCF = 249.8 Hz), 146.8, 144.2, 142.5, 136.6, 133.9, 133.8, 133.1 (d, JCF = 3.6 Hz), 131.8 (d, JCF = 7.9 Hz), 128.9, 126.0, 124.0, 123.7, 122.8, 119.9, 119.7, 117.9, 116.7 (d, JCF = 21.6 Hz), 100.6, 44.8, 31.4, 29.0, 26.4, 22.5, 14.0; anal. calcd for C56H46F2N2O2: C, 82.33; H, 5.68; N, 3.43. Found: C, 82.23; H, 5.55; N, 3.48; HRMS (+ESI): calcd for C56H47F2N2O2 m/z 817.3600 [M + H]+, found m/z 817.3597 [M + H]+.
6,15-Dihexyl-7,16-bis(4-isopropylphenyl)-6,15-dihydroindeno[1,2-b]indeno[2′,1′:5,6]indolo[2,3-h]carbazole-9,18-dione (9d). Yield 95%, orange crystals, mp > 370 °C; IR (DRA): ν = 3059, 2958, 2926, 2866, 1705, 1609, 1530, 1466, 1406, 1346, 1287, 1244, 1185, 1154, 1092, 1057, 1017, 984, 919, 839, 808, 758, 723, 623 cm−1; 1H NMR (400 MHz, CDCl3): δ = 7.61–7.50 (m, 12H), 7.41 (td, J = 7.4, 0.8 Hz, 2H), 7.25 (s, 2H), 7.23–7.18 (m, 2H), 6.58 (s, 2H), 3.96–3.86 (m, 4H), 3.25–3.14 (m, 2H), 1.66–1.57 (m, 4H), 1.53 (d, J = 6.9 Hz, 12H), 1.28–1.20 (m, 4H), 1.19–1.11 (m, 4H), 0.97–0.83 (m, 10H); 13C NMR (126 MHz, CDCl3): δ = 192.6, 150.1, 146.6, 144.4, 142.2, 136.7, 134.5, 133.7, 133.5, 129.9, 128.7, 127.5, 125.7, 124.0, 123.5, 123.0, 120.2, 119.8, 118.8, 100.3, 44.8, 34.4, 31.3, 29.1, 26.3, 24.3, 22.6, 14.0; HRMS (+ESI): calcd for C62H62I2N2O2 m/z 1120.2895 [M], found m/z 1120.2899 [M].
6,15-Dihexyl-7,16-bis(5-methylthiophen-2-yl)-6,15-dihydroindeno[1,2-b]indeno[2′,1′:5,6]indolo[2,3-h]carbazole-9,18-dione (9e). Yield 76%, orange needles, mp 361–362 °C; IR (DRA): ν = 3069, 2927, 2853, 1697, 1608, 1516, 1465, 1409, 1344, 1286, 1245, 1227, 1187, 1154, 1120, 1090, 982, 909, 847, 800, 777, 758, 723, 622 cm−1; 1H NMR (400 MHz, CDCl3): δ = 7.59 (d, J = 3.8 Hz, 2H), 7.57 (d, J = 3.9 Hz, 2H), 7.46–7.39 (m, 2H), 7.31 (s, 2H), 7.24–7.20 (m, 2H), 7.13–7.07 (m, 4H), 7.00 (s, 2H), 4.20–3.99 (m, 4H), 2.74 (s, 6H), 1.77–1.67 (m, 4H), 1.37–1.23 (m, 8H), 1.22–1.12 (m, 4H), 0.91 (t, J = 7.0 Hz, 6H); 13C NMR (101 MHz, CDCl3): δ = 192.4, 146.8, 144.4, 142.6, 142.5, 136.8, 135.0, 134.7, 133.7, 128.7, 128.7, 126.3, 126.1, 125.5, 123.5, 122.7, 120.3, 119.8, 112.0, 100.6, 44.9, 31.4, 29.5, 26.6, 22.6, 15.4, 13.9; anal. calcd for C54H48N2S2O2: C, 78.99; H, 5.89; N, 3.41. Found: C, 78.76; H, 5.97; N, 3.78.

General procedure for reduction of fused ICZ-based compounds 9a,e

Reduction of compounds 9a,e was performed in a two-neck 100 ml round-bottomed flask which equipped with a magnetic stir bar, a dropping funnel and a reflux condenser. Anhydrous AlCl3 (1.7 g, 12.8 mmol) was added portionwise to a stirring suspension of LiAlH4 (420 mg, 11 mmol) in dry THF (30 ml) under external cooling and a slight stream of dry argon. The solution of compound 9a or 9e (0.35 mmol) in dry THF (30 ml) was added slowly to this mixture at ambient temperature. After the addition was completed, the reaction mixture was refluxed for 4 h under an argon atmosphere. The excess AlH3 was destroyed by the successive addition of MeOH (1 ml), a 15% solution of NaOH (0.5 ml), and water (0.5 ml). The inorganic precipitate was filtered and washed with warm THF (2 × 10 ml). The combined THF filtrates were concentrated under vacuum and the solid residue was purified by recrystallization from DMF (10 ml). The resulting crystalline precipitate was filtered, washed with EtOH (3 × 2 ml) and dried at 120 °C to give compound 10a or 10e in the analytically pure form.
6,15-Dihexyl-7,16-diphenyl-6,9,15,18-tetrahydroindeno[1,2-b]indeno[2′,1′:5,6]indolo[2,3-h]carbazole (10a). Yield 76%, light yellow crystals, mp 345–346 °C; IR (DRA): ν = 3055, 2959, 2926, 2853, 1620, 1520, 1448, 1402, 1348, 1329, 1311, 1238, 1224, 1134, 1084, 1056, 1024, 974, 951, 872, 836, 764, 756, 739, 721, 704 cm−1; 1H NMR (400 MHz, C6D6): δ = 7.85 (s, 2H), 7.79 (d, J = 7.5 Hz, 2H), 7.76–7.72 (m, 4H), 7.45–7.39 (m, 6H), 7.28–7.22 (m, 4H), 7.14–7.12 (m, 2H), 7.05 (s, 2H), 3.97–3.88 (m, 4H), 3.59 (s, 4H), 1.66–1.56 (m, 4H), 1.22–1.13 (m, 4H), 1.09–1.00 (m, 4H), 0.97–0.88 (m, 4H), 0.85 (t, J = 7.3 Hz, 6H); 13C NMR (126 MHz, CDCl3): δ = 144.4, 142.5, 142.3, 139.4, 139.1, 133.3, 133.0, 130.7, 129.0, 128.0, 126.5, 126.3, 124.9, 122.9, 122.4, 119.6, 118.4, 117.5, 99.0, 44.6, 36.4, 31.5, 28.6, 26.4, 22.6, 14.0; anal. calcd for C56H52N2: C, 89.32; H, 6.96; N, 3.72. Found: C, 89.10; H, 7.02; N, 3.80.
6,15-Dihexyl-7,16-bis(5-methylthiophen-2-yl)-6,9,15,18-tetrahydroindeno[1,2-b]indeno[2′,1′:5,6]indolo[2,3-h]carbazole (10e). Yield 87%, light yellow crystals, mp 315–316 °C; IR (DRA): ν = 3058, 2922, 2853, 1621, 1568, 1514, 1494, 1466, 1446, 1402, 1331, 1309, 1290, 1221, 1193, 1163, 1122, 1081, 1051, 1005, 975, 951, 837, 803, 765, 756, 723, 659, 518 cm−1; 1H NMR (400 MHz, CDCl3): δ = 7.88 (d, J = 7.4 Hz, 2H), 7.65 (s, 2H), 7.51 (d, J = 7.3 Hz, 2H), 7.38 (td, J = 7.5, 0.5 Hz, 2H), 7.30–7.27 (m, 2H), 7.14 (d, J = 3.3 Hz, 2H), 7.06–7.02 (m, 2H), 6.93 (s, 2H), 4.20–3.98 (m, 4H), 3.88 (s, 4H), 2.74 (s, 6H), 1.78–1.67 (m, 4H), 1.39–1.13 (m, 12H), 0.91 (t, J = 7.0 Hz, 6H); 13C NMR (126 MHz, CDCl3): δ = 144.5, 142.4, 142.3, 141.5, 139.8, 136.8, 134.4, 133.7, 128.2, 126.5, 126.4, 125.7, 125.0, 123.9, 122.5, 119.7, 118.5, 110.4, 99.2, 44.6, 36.6, 31.5, 29.0, 26.7, 22.7, 15.7, 14.1; HRMS (+ESI): calcd for C54H52N2S2 m/z 792.3566 [M], found m/z 792.3566 [M].

General procedure for methylation of the reduced compounds 10a,e

Compound 10a or 10e (0.2 mmol) and MeI (680 mg, 4.8 mmol) were dissolved in dry THF (10 ml) under an argon atmosphere and KOt-Bu (480 mg, 4.8 mmol) in dry THF (5 ml) was added dropwise to this solution. The reaction mixture was stirred at ambient temperature for 1 h, filtered through a short silica gel pad and evaporated giving the solid residue of crude product. The latter was purified by crystallization from DMF (5 ml); the resulting precipitate was filtered, washed with EtOH (3 × 2 ml) and dried at 120 °C to give compound 11a or 11e in the analytically pure form.
6,15-Dihexyl-9,9,18,18-tetramethyl-7,16-diphenyl-6,9,15,18-tetrahydroindeno[1,2-b]indeno[2′,1′:5,6]indolo[2,3-h]carbazole (11a). Yield 80%, light yellow crystals, mp 308–309 °C; IR (DRA): ν = 3053, 2952, 2933, 2857, 1619, 1519, 1489, 1464, 1444, 1401, 1336, 1298, 1246, 1227, 1154, 1121, 1107, 1070, 1022, 973, 886, 842, 826, 777, 752, 740, 716, 701 cm−1; 1H NMR (400 MHz, C6D6): δ = 7.77–7.72 (m, 4H), 7.68–7.64 (m, 4H), 7.42–7.37 (m, 6H), 7.32–7.20 (m, 6H), 6.72 (s, 2H), 3.99–3.94 (m, 4H), 1.65–1.56 (m, 4H), 1.48 (s, 12H), 1.21–1.11 (m, 4H), 1.08–0.99 (m, 4H), 0.95–0.86 (m, 4H), 0.84 (t, J = 7.3 Hz, 6H); 13C NMR (126 MHz, CDCl3): δ = 154.6, 144.0, 142.4, 139.8, 139.3, 137.0, 132.8, 130.7, 128.9, 128.0, 126.8, 126.7, 122.9, 122.6, 122.6, 119.7, 117.4, 116.1, 99.0, 45.8, 44.6, 31.5, 28.8, 27.7, 26.4, 22.6, 14.1; HRMS (+ESI): calcd for C60H60N2 m/z 808.4751 [M], found m/z 808.4759 [M].
6,15-Dihexyl-9,9,18,18-tetramethyl-7,16-bis(5-methylthiophen-2-yl)-6,9,15,18-tetrahydroindeno[1,2-b]indeno[2′,1′:5,6]indolo[2,3-h]carbazole (11e). Yield 81%, light yellow crystals, mp 311–312 °C; IR (DRA): ν = 3057, 2953, 2921, 2857, 1684, 1620, 1464, 1446, 1401, 1337, 1297, 1247, 1218, 1155, 1106, 1068, 1049, 1003, 973, 884, 843, 803, 775, 753, 717, 569, 522 cm−1; 1H NMR (400 MHz, CDCl3): δ = 7.82 (d, J = 7.0 Hz, 2H), 7.58 (s, 2H), 7.42 (d, J = 7.3 Hz, 2H), 7.37–7.27 (m, 4H), 7.13 (d, J = 2.8 Hz, 2H), 7.07 (dd, J = 3.2, 0.8 Hz, 2H), 6.64 (s, 2H), 4.28–4.10 (m, 4H), 2.75 (s, 6H), 1.83–1.71 (m, 4H), 1.40 (s, 12H), 1.35–1.16 (m, 12H), 0.92 (t, J = 7.0 Hz, 6H); 13C NMR (126 MHz, CDCl3): δ = 154.6, 144.4, 142.3, 141.6, 139.9, 137.4, 137.0, 134.2, 128.3, 126.9, 126.8, 125.4, 124.1, 122.7, 122.5, 119.8, 116.3, 110.3, 99.1, 45.9, 44.6, 31.5, 29.2, 27.8, 26.7, 22.7, 15.5, 14.1; HRMS (+ESI): calcd for C58H60N2S2 m/z 848.4192 [M], found m/z 848.4190 [M].

Acknowledgements

This work was supported by the Russian Foundation for Basic Research (research projects No. 15-03-00924_A, 14-03-01017_A, 14-03-00479_A) and the Scientific Council of the President of the Russian Federation (grant MK-4509.2016.3).

Notes and references

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Footnotes

Electronic supplementary information (ESI) available: Copies of 1H and 13C NMR spectra of all new compounds. Photophysical, cyclic voltammetry and TGA data for compounds 9a–e and 11a,e (PDF), as well as crystallographic data for compound 9a (CIF). CCDC 1478325. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6ra11796a
About 10 mg of palladium metal was collected; it was 92% based on Pd(OAc)2.

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