Syntheses, crystal structures, and physical properties of copper complexes with dimethylthio-pyrazino-selenathiafulvalene (=Dmt-Pyra-STF) as ligand: trans-[CuCl2(Dmt-Pyra-STF)2] and [Cu2Br2.5(Dmt-Pyra-STF)]

New copper complexes with Dmt-Pyra-STF (=dimethylthio-pyrazino-selenathiafulvalene) as the ligand-trans-[(CuCl2)-Cl-II(Dmt-Pyra-STF)(2)] (1) and [(Cu2Br2.5)-Br-I(Dmt-Pyra-STF)] (2)-have been synthesized by a vertical diffusion method. In complex 1, the donors form uniform stacking columns along the c axis to have a theta-type donor arrangement, but I is an insulator due to the absence of carriers. The magnetic susceptibility of I can be fitted to the Curie-Weiss rule (theta = -9.02 K) and suggests that the oxidation state of Cu ions in I is 2+. In contrast, complex 2 has supramolecular chains along the c axis, which are formed by Cut and Br-. In addition, this complex is a semiconductor with sigma(rt) = 0.16 S cm(-1) and E-a = 0.10 eV. The magnetic susceptibility of 2 suggests that the oxidation state of Cu ions in 2 is 1 +, namely [(Cu2Br2.5)-Br-I(Dmt-Pyra-STF)(0.5+)]. Both complexes 1 and 2 demonstrate that pyrazino-fused STF derivatives can be coordinated to a copper even though the atomic orbital of Se is so large. Furthermore, we can firstly synthesize complex 2, in which both charge transfer and coordination occur simultaneously. (C) 2008 Elsevier Masson SAS. All rights reserved.