A new BEDT-TTF BEDT-TTFsBis ethylenedithio.tetrathiafulvalene.-based cation radical salt BEDT-TTF.2HgCl3PTCE TCEs 1,1,2-trichloroethane.was synthesized by using oxidative electro-crystallization at a constant current. Its structure was determined by four-circle X-ray diffraction method. The crystal belongs to monoclinic system, C2 space group with the unit cell parameters of as39.236 (5). A°, bs6.676 (1) A°, cs14.881 (3). A°, bs95.58 2.0, Vs3879.4 12. A°(3), Zs4. The structure shows that the BEDT-TTF radicals are stacked to form columns along the c-axis and arranged side-by-side to form one-dimensional uniform chains along the b-axis. The one-dimensional polymer HgCl3.nny, together with neutral TCE molecules, is also along the b-axis. Cationic BEDT-TTF sheets and anionic HgCly3 sheets are sandwiched along the a-axis. The room temperature resistivity of the single crystal was measured to be 3.33 VPm on the bc-plane. Its resistivity–temperature curve demonstrates a semiconductor behavior with an activation energy of 0.308 eV.

Several donor-p-donor (D-p-D), acceptor-p-acceptor (A-p-A), and donor-p-acceptor (D-p-A) types of organic compounds with fluorene as p bridge and dimesitylboryl group as electron acceptor, which show strong two-photon excited blue fluorescence, have been synthesized and structurally investigated. The symmetric A-p-A type of compound exhibits the shortest wavelength of twophoton excited fluorescence (TPEF) at λem=405 nm under the excitation of λex=730nm; the unsymmetric D-p-A type of compound with diphenylamino as donor exhibits the most intense TPEF at blue region (λem=484 nm) with a two-photon absorption cross-section of 425GM under λex=800nm.

A new electrical conductive crystal PyEt[Ni(dmit)2]2 (dmit=4,5-dimercapto-1,3-dithiole-2-thione) has been synthesized and its X-ray structure has been determined to be in monoclinic system, C2/c space group. In PyEt[Ni(dmit)2]2 crystal, the conducting component [Ni(dmit)2]0.5− is face-to-face packed forming molecular column along the c-direction, and these molecular columns are then side-by-side extended along the a-direction forming a kind of two-dimensional conducting sheet on (010). The measured conductivity at room temperature along a certain direction on (010) plane is 10 S cm−1. From 282 to 269 K, the crystal shows metallic behavior but changes to semiconductor below 269 K. Based on the measured crystal structure and calculated band structure, this conductor-semiconductor phase transformation can be primarily interpreted: The metallic conductivity is corresponding to the uniform molecular column and the atomic-lattice-chain structure of Ni chain, while the semi-conductive behavior to staggered molecular column and the atomic-zigzag-chain structure of Ni chain.

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.