A series of pyrene-fused thioxanthenes have been synthesized via a new concise route, and their crystal structures and photophysical properties have been fully investigated. The eight-ring fused dipyrene–thioxanthene (DPTA) can crystallize to monoclinic and triclinic X-ray structures, and their precursor has been isolated as two stable atropisomers with different photophysical properties. The EHOMO becomes higher and the Eg become narrower as more thioxanthene unit being fused with pyrene.

Compact molecular packing with short π-π stacking and large π-overlap in organic semiconductors is desirable for efficient charge transport and high carrier mobility. Thus charge transport anisotropy along different directions is commonly observed in organic semiconductors. Interestingly, in this article, we found that comparable charge transport property were achieved based on the single crystals of a bis-fused tetrathiafulvalene derivative (EM-TTP) compound along two interaction directions, that is, the multiple strong S···S intermolecular interactions and the π-π stacking direction, with the measured electrical conductivity and hole mobility of 0.4 S cm−1, 0.94 cm2 V−1 s−1 and 0.2 S cm−1, 0.65 cm2 V−1 s−1, respectively. This finding provides us a new molecular design concept for developing novel organic semiconductors with isotropic charge transport property through the synergistic effect of multiple intermolecular interactions (such as S···S interactions) and π-π stacking.

Several cyclized indole derivatives have been synthesized, and their structures been determined. The C3-symmetric single-chiral N-phenyltriindole (Tr-Ph3) crystallized in the P1 space group, and the S4-symmetric saddle-like tetraindole (TTr) crystallized in the I4̅ space group. The Tr-Ph3 and TTr crystals exhibit remarkable powder SHG intensities 5 and 11 times that of KH2PO4 (KDP), respectively. TTr is a useful octupolar core to build S4-symmetric molecules and crystals for second-NLO materials.

By π-extending and ring-capping the bis-fused TTF moiety (namely TTP), several electrically conductive crystals of 12-S-atom TTP derivatives have been synthesized: (1) bis(vinylenedithio)-TTP which can be isolated as triclinic P (t-BV-TTP) and monoclinic P21 (m-BV-TTP) polymorphs separately, (2) bis(ethylenedithio)-TTP (BE-TTP), (3) ethylenedithio-methylenedithio-TTP (EM-TTP), (4) ethylenedithio-vinylenedithio-TTP (EV-TTP). The structures of t-BV-TTP and EM-TTP crystals can be classified as all-parallel β-type, in which all molecules in the same 2-D molecular slab or in different slabs are all parallel packed. In contrast, m-BV-TTP and BE-TTP crystals can be described as herring-bone β-type, in which the molecules in neighboring 2-D slabs are alternately in two directions. Among the above four β-type structures, the EM-TTP crystal shows the highest conductivity (σ = 7 × 10−3 Ω−1 cm−1 along [100] direction). The EV-TTP crystal belongs to a kind of three-by-three κ-type structure and its conductivity was measured to be 3 × 10−3 Ω−1 cm−1 along [100] direction. The calculated hole mobilities of the title TTP derivatives, by DFT method and the host-caged approach, are larger than that of the dithiophene-TTF (DT-TTF) crystal.

Bridging the triindole core and triarylboryl acceptor by an ethenylene linker at the 3,8,13- or 2,7,12-position, the resultant 3-BET and 2-BET show two-photon absorption (TPA) cross sections of δ = 2100 and 2500 GM (at 810 nm by femtosecond pulses in THF), respectively. The TPA enhancement of the 2,7,12-isomers is also found when comparing 3-BYT and 2-BYT (δ = 870 and 1900 GM) and 3-NET and 2-NET (36 and 400 GM).

A new molecular conductor (n-Bu4N)[Ni(dmit)2]4·MeCN (dmit = 2-thioxo-1,3-dithiole-4,5-dithiolato) has been synthesized and its X-ray structure has been determined. The crystal exhibits conductivity 0.1 Ω−1 cm−1 at room temperature and a semi-conducting behavior with small activation energy of 0.170 eV (at 295 K) and 0.065 eV (at 95 K). The coordination anions are arranged in a parallel fashion in the crystal forming two-dimensional networks, in which the face-to-face π–π longitudinal intermolecular interactions are stronger than the side-by-side S⋯S transverse interactions. The anionic stacks along the b-direction exhibit a type of tetrad structure. Infrared spectra suggest that the tetrad {4[Ni(dmit)2]}− may consist of one mono-anion [Ni(dmit)2]− and three neutral [Ni(dmit)2] units. The bond analysis further suggests that the single electron in the HOMO of [Ni(dmit)2]− can delocalize to its two neighboring [Ni(dmit)2] molecules to some extent.In a tetrad {[Ni1][Ni2][Ni3][Ni4]}−, the HOMO electron’s home is at [Ni2] and the electron can leave to visit its neighbors [Ni1] [Ni3], but rarely go to [Ni4].

Both the title multi-sulfur molecules C5H2S5 (1) and C5H2OS4 (2) have a chair conformation, while molecule 1 has a higher degree of π-conjugation. Both the crystals are characterized by short S···S intermolecular contacts and by face-to-face column-like packing style, but crystal 1 has been more stabilized which may be the result of its stronger π–π intermolecular interactions. Compound 1 crystallizes in non-centrosymmetric polar space group Pmn21 with a = 10.6826(17), b = 9.3633(11), c = 4.0764(6) Å, V = 407.74(10) Å3, and Z = 2. The molecular dipole moment of 1 is ±62.5(1)° away from the macro-polarization direction along the c-axis. Consequently, the crystalline powder of crystal 1 exhibit a second harmonic generating (SHG) intensity 0.5 time strong as that of urea standard powder crystals when irradiated by a 1,080 nm of Nd:YAP laser beam. Compound 2 shows no SHG effect because it crystallizes in centrosymmtric space group Pbca with a = 11.4208(8), b = 7.8843(9), c = 33.587(3) Å, V = 3024.3(5) Å3, and Z = 16.Structures and Non-linear Optical Properties of Multi-Sulfur π-Conjugated Compounds 4,5-Vinylenedithio-1,3-dithiole-2-thione (C5H2S5) and 4,5-Vinylenedithio-1,3-dithiole-2-one (C5H2OS4)Gang Xue, Qi Fang,* Wen-Tao Yu, Xia Chen, and Hong Lei