Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, Vol.269, 133-147, 1995
4 New Et-Based and TTM-TTF-Based CT Salts with Cu-Containing Binuclear Polyhalide Complex Anions - Synthesis, Properties, and Structure
Four new CT salts with Cu-containing binuclear polyhalide complex anions ET(3)Cu(2)Br(x)(x similar to 5) (A), ET(3)Cu(2)Cl(4) (B), (TTM-TTF) Cu2Br4.72 (C), and (TTM-TTF)(2) Cu2Cl6 (D) [ET=BEDT-TTF=bisethylenedithio-tetrathiafulvalene, TTM-TTF=tetrathiomethyl-tetrathiafulvalene] are prepared and the degree of charge transfer as well as the valence states of the Cu atom in the four CT salts are discussed based on the analysis of X-ray photoelectron spectroscopy. The conductivity of the four charge-transfer salts A, B, C, and D at room temperature and their temperature dependence from room temperature down to 77 K along the crystal growth direction are reported. A behaves metallic down to about 250 K, then turns to a semi-conductor; B is an organic metal down to liquid nitrogen temperature; C shows a semi-conducting behavior down to about 230 K, then turns to an insulator and D is an insulator. The crystal structures of C and D are determined. In crystal C, both donors and accepters occupy symmetry centers in the cell and are stacked in segregated columns. We have observed short intracolumnar and intercolumnar S...S contacts of 3.214(10), 3.417(12)Angstrom, respectively in the donor columns; the binuclear polybromide metal complex acceptor anions are planar and stacked forming complicated polymeric columns along the b axis, the Cu atom of each of the polymeric columns is five-coordinate. In crystal D, the donor molecules TTM-TTF form dimers and the plane is almost perpendicular to that of the metal complex anion (Cu2Cl6)(2-).