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.

Three s-triazine derivatives have been synthesized and their structures been de-termined. These are Compound I: 2,4-Dimethyl-6-(p-N, N-dimethylaminostyryl)-s-triazine (ab-breviated to NMe-1), Compound II: 2, 4-Dimethyl-6-(p-N, N-diethylaminostyryl)-s-triazine (to NEt-1), and Compound III: 2-Methyl-4, 6-bis(p-N, N-dimethylaminostyryl)-s-triazine (NMe-2). NMe-1 and NEt-1 molecules belong to the D-π-A type with a one-dimensional charge-transfer character. NMe-1 crystallize to centrosymmetric 1P space group, while NEt-1 to non-centro- sym- metric polar Cc space group with all of the molecular charge-transfer axes taking the same orientation. Under the irradiation of 1064 nm fundamental laser, NEt-1 powder crystals radiate a 2-order harmonic light with an intensity 46.8 times that of urea. The Λ typed NMe-2 molecule, which has a two-dimensional charge-transfer character, crystallize to polar P21 space group. Its powder crystals exhibit a 2-order harmonic intensity 46.2 times that of urea. The quantum chemical calculations and tensor analyses have been carried out to reveal the dependence of the macro 2-order nonlinear optical (NLO) efficiency on the micro 2-order NLO coefficients (β) and on the crystalline packing styles.

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.

Two series of multibranched compounds with vinylenes attaching to the s-triazine core have been synthesized. The twophoton absorption cross section σ increases significantly as the branch number increases, with the ratios of between one-, two-, and three-branched compounds being 1.0:3.3:7.0 for series A and 1.0:3.7:7.0 for series B respectively, indicating remarkable cooperative enhancement.