We have synthesized a series of new D−π−A compounds that feature various electron donors and a fixed benzothiazolyl unit as an electron acceptor. The crystal structure of compound 3 [trans,trans-2-{4-[(4-N-carbazolyl)styryl]styryl}-1,3-benzothiazole, CSSB] was determined. All these compounds show high fluorescence quantum yields and 3 in toluene gives the most intense blue emission around 450 nm with a quantum yield of Φ = 0.69. When excited at 800 nm by a Ti: sapphire femtosecond laser, these compounds exhibit strong two-photon-excited fluorescence (TPEF) in the blue-to-orange region. The measured TPEF cross-section of compound 2 [trans,trans-2-{4-[4-(N,N-diphenylamino)styryl]- styryl}-1,3-benzothiazole, DPSSB], for example, is about 6.1 times that of Coumarin 307. hotophysical data indicate that these compounds are polar in the ground state and have an enhanced polarity in the excited state, and that the electron donating ability of a dialkylamino group is much stronger than that of a diarylamino group.

Electrically conductive platelet crystals of Z[Pd(dmit)2]2 [Z = (Me3NEt), (MeNEt3), (NEt4)], as well as their precursors Z2 [Pd (dmit) 2], have been synthesized by a non-electrochemical method and their structures have been determined. The single-crystal conductivities at a direction on the cleavage surface at room temperature were measured to be 58 Ω 1 cm 1 for (Me3NEt)[Pd(dmit)2]2, 5.0 Ω 1 cm 1 for (MeNEt3)[Pd(dmit)2]2 and 2.2 Ω 1 cm 1 for (NEt4)[Pd(dmit)2]2, respectively. This sequence of conductivity is agreement with the sequence of structural twodimensionality of these three complexes. The resistivity–temperature curves reveal the semiconducting behavior of the above complexes, which show very narrow band gaps. The structure analysis results reveals that when the size of cation Z in Z[Pd(dmit)2]2 is finely tuned [(Me4N)+→(Me3NEt)+→(Me2NEt2)+→(MeNEt3)+→(NEt4)], the corresponding complexes belong to the same structural motif and each individual possesses some special structural characteristics. Subtle structural difference in this group of complexes can severely influence their measured conductivities and significantly influence their calculated band structures.

three-branched octupolar compound, 2,4,6-tris[2-(4-N,N-diethylamino)phenylethenyl]-1,3,5-s-triazine (compound III), as well as its one-and two-branched analogues (compounds I and II respectively) have been synthesized. The structures of I and II have been determined by X-ray diffraction. The linear and nonlinear spectra of these compounds regularly vary: (1) the spectral positions (lmax values) of the linear absorption, the single-photon excited fluorescence (SPEF) and the two-photon excited fluorescence (TPEF) show regular redshifts when the branch number increases from 1 to 3; (2) the spectral intensities, including the linear absorbance emax and the two-photon absorption cross-section s, the SPEF and the TPEF intensities are all increased significantly when going from I to III. The values of emax/MW and s/MW (of compounds I, II and III) vary with the ratios of 1.0: 1.3: 1.7 and 1.0: 1.4: 1.3, respectively. All the photophysical data indicate that by incorporating more branches into the triazine ring, the linear and nonlinear optical responses have been significantly enhanced, and that the spectral behaviour of II is closer to that of III, while more different from that of I. The single-branched compound I crystallizes in the noncentrosymmetric polar space group Cc. Its crystalline powder sample shows remarkable macro second-order nonlinear response with a SHG intensity of 46.8 times that of urea under a fundamental picosecond Nd: YAG laser beam (1064 nm). An important factor of such a large SHG intensity is that all the molecular dipoles take the same-oriented packing style that makes the crystal maximally polarized, fulfilling the optimization in the sense of crystal engineering.

We have synthesized two new organic salts, trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-Nmethylpyridinium toluene-p-sulfonate (abbreviated as HMASPS) and trans-4-[p-(N-hydroxyethyl-Nethylamino) styryl]-N-methylpyridinium toluene-p-sulfonate (abbreviated as HEASPS). X-Ray iffraction analyses reveal that HMASPS crystal belongs to the P21/n space group, with water olecules co-crystallized in the crystal and forming the monohydrate with the formula of C17H21N2Oz?C7H7O3S2?H2O, while HEASPS belongs to the P1

A new molecular conductor (PyMe)[Ni(dmit)2]2 (PyMe=N-methylpyridinium, dmit= 2-thioxo-1,3-dithiole-4,5-dithiolato) has been synthesized and its structure been determined. The temperature-dependent conductivities in the range of 290-20K reveal a semi-conducting behavior of the crystal with a small activation energy of 0.067 eV and a quite high room temperature conductivity of 2 Scm 1.