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-[CuIICl2(Dmt-Pyra-STF)2] (1) and [CuI2Br2.5(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 θ-type donor arrangement, but 1 is an insulator due to the absence of carriers. The magnetic susceptibility of 1 can be fitted to the Curie–Weiss rule (θ = −9.02 K) and suggests that the oxidation state of Cu ions in 1 is 2+. In contrast, complex 2 has supramolecular chains along the c axis, which are formed by CuI and Br−. In addition, this complex is a semiconductor with σrt = 0.16 S cm−1 and Ea = 0.10 eV. The magnetic susceptibility of 2 suggests that the oxidation state of Cu ions in 2 is 1+, namely [CuI2Br2.5(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.

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