Extended bis(benzothia)quinodimethanes and their dications were synthesized as stable species. The neutral compounds mainly have a quinoidal structure in the ground state but show increased diradical character with extension of the central quinodimethane unit. The dications exhibit similar electronic absorption spectra, NMR spectra, NICS values, and diatropic ring currents to their aromatic all-carbon acene analogues and thus can be regarded as genuine isoelectronic structures of pentacene, hexacene, and heptacene, respectively. Our research gave some insights into the design and synthesis of stable longer acene analogues.

Acene-based materials have promising applications for organic electronics but the major constrain comes from their poor stability. Herein a new strategy to stabilize reactive acenes, by fusion of an anti-aromatic pentalene unit onto the zigzag edges of two acene units to form a Z-shaped acene dimer, is introduced. The Z-shaped acene dimers are extremely stable and show a small energy gap resulting from intramolecular donor–acceptor interactions. X-ray crystallographic analysis revealed their unique geometry and one-dimensional slip-stack columnar structure. Besides optical and electrochemical characterizations, solution-processed field-effect transistors were also fabricated.

Extended bis(benzothia)quinodimethanes and their dications were synthesized as stable species. The neutral compounds mainly have a quinoidal structure in the ground state but show increased diradical character with extension of the central quinodimethane unit. The dications exhibit similar electronic absorption spectra, NMR spectra, NICS values, and diatropic ring currents to their aromatic all-carbon acene analogues and thus can be regarded as genuine isoelectronic structures of pentacene, hexacene, and heptacene, respectively. Our research gave some insights into the design and synthesis of stable longer acene analogues.

Acene-based materials have promising applications for organic electronics but the major constrain comes from their poor stability. Herein a new strategy to stabilize reactive acenes, by fusion of an anti-aromatic pentalene unit onto the zigzag edges of two acene units to form a Z-shaped acene dimer, is introduced. The Z-shaped acene dimers are extremely stable and show a small energy gap resulting from intramolecular donor–acceptor interactions. X-ray crystallographic analysis revealed their unique geometry and one-dimensional slip-stack columnar structure. Besides optical and electrochemical characterizations, solution-processed field-effect transistors were also fabricated.

Quinoidal thia-acene analogues, as the respective isoelectronic structures of pentacene and nonacene, were synthesized and an unusual 1,2-sulfur migration was observed during the Friedel–Crafts alkylation reaction. The analogues display a closed-shell quinoidal structure in the ground state with a distinctive dipolar character. In contrast to their acene isoelectronic structures, both compounds are stable because of the existence of more aromatic sextet rings, a dipolar character, and kinetic blocking. They exhibit unique packing in single crystals resulting from balanced dipole–dipole and [CH⋅⋅⋅π]/[CH⋅⋅⋅S] interactions.

Quinoidal thia-acene analogues, as the respective isoelectronic structures of pentacene and nonacene, were synthesized and an unusual 1,2-sulfur migration was observed during the Friedel–Crafts alkylation reaction. The analogues display a closed-shell quinoidal structure in the ground state with a distinctive dipolar character. In contrast to their acene isoelectronic structures, both compounds are stable because of the existence of more aromatic sextet rings, a dipolar character, and kinetic blocking. They exhibit unique packing in single crystals resulting from balanced dipole–dipole and [CH⋅⋅⋅π]/[CH⋅⋅⋅S] interactions.

Three soluble and stable thienoacene-fused pentalene derivatives (1–3) with different π-conjugation lengths were synthesized. X-ray crystallographic analysis and density functional theory (DFT) calculations revealed their unique geometric and electronic structures due to the interaction between the aromatic thienoacene units and antiaromatic pentalene moiety. As a result, they all possess a small energy gap and show amphoteric redox behaviour. Time dependent (TD) DFT calculations were used to explain their unique electronic absorption spectra. These new compounds exhibited good thermal stability and ordered packing in solid state and thus their applications in organic field-effect transistors (OFETs) were also investigated. The highest field-effect hole mobility of 0.016, 0.036 and 0.001 cm² V⁻¹ s⁻¹ was achieved for solution-processed thin films of 1–3, respectively.

A pyromellitic diimide building block, 2,6-bis(2-decyltetradecyl)−4,8-di(thiophen-2-yl)pyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetraone (4), is synthesized. Based on this building block and other electron-rich units such as 2,2′-bithiophene, thieno[3,2-b]thiophene and 4,8-bis(dodecyloxy)benzo[1,2-b:4,5-b′]dithiophene, three conjugated polymers P1, P2, and P3 are prepared in good yield via Stille coupling polymerization. These new copolymers have good solubility in common organic solvents and exhibit good thermal stability. The optical, electrochemical, and thermal properties of these polymers P1–P3 are carefully investigated, and their applications in solution-processed organic field-effect transistors are also studied. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2454–2464

A series of unsymmetrical naphthalene imide derivatives (1a, 1b, 2, 3, 4, 5) with high electron affinity was synthesized and used in n-channel organic field-effect transistors (OFETs). They have very good solubility in common organic solvents and good thermal stability up to 320 °C. Their photophysical, electrochemical, and thermal properties were investigated in detail. They showed low-lying LUMO energy levels from −3.90 to −4.15 eV owing to a strong electron-withdrawing character. Solution-processed thin-film OFETs based on 1a, 1b, 2, 3, 4 were measured in both N₂ and air. They all showed n-type FET behavior. The liquid-crystalline compounds 1a, 1b, and 3 showed good performance owing to the self-healing properties of the film in the liquid-crystal phase. Compound 3 has an electron mobility of up to 0.016 cm² V⁻¹ s⁻¹ and current on/off ratios of 10⁴–10⁵.

A p-quinodimethane (p-QDM)-bridged porphyrin dimer 1 has been prepared for the first time. An unexpected Michael addition reaction took place when we attempted to synthesize compound 1 by reaction of the cross-conjugated keto-linked porphyrin dimers 8 a and 8 b with alkynyl/aryl Grignard reagents. Alternatively, compound 1 could be successfully prepared by intramolecular Friedel–Crafts alkylation of the diol-linked porphyrin dimer 14 with concomitant oxidation in air. Compound 1 shows intense one-photon absorption (OPA, λ_max=955 nm, ε=45400 M⁻¹ cm⁻¹) and a large two-photon absorption (TPA) cross-section (σ⁽²⁾_max=2080 GM at 1800 nm) in the near-infrared (NIR) region due to its extended π-conjugation and quinoidal character. It also exhibits a short singlet excited-state lifetime of 25 ps. The cyclic voltammogram of 1 displays multiple redox waves with a small electrochemical energy gap of 0.86 eV. The ground-state geometry, electronic structure, and optical properties of 1 have been further studied by density functional theory (DFT) calculations and compared with those of the keto-linked dimer 8 b. This research has revealed that incorporation of a p-QDM unit into the porphyrin framework had a significant impact on its optical and electronic properties, leading to a novel NIR OPA and TPA chromophore.

Synthesis of n-type organic semiconductors with high electron mobilities, good environmental stability, and good processability is an urgent task in current organic electronics. This is because most of π-conjugated materials are p-type and prefer to transport positive hole carriers. In this article, a series of new dicarboxylic imide-substituted poly(p-phenylene vinylenes) (DI-PPVs) were first synthesized. They exhibited a high electron affinity of 3.60 eV and thus are able to transport electrons. The polymers showed tunable solubility in common organic solvents and high chemical and thermal stability. They remain rigidity of the PPV backbone, and strong interchain π-stacking was observed in thin films by X-ray diffraction measurement. All these suggested that these polymers could serve as good candidates as n-type semiconductors in organic electronic devices such as n-channel field-effect transistors and all polymer-based solar cells. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 186–194, 2010