A New Conducting Molecular Solid Based on the Magnetic [Ni(dmf) 6] 2+ Cation and on [Ni(dsit) 2] 22− (dsit=1,3-dithiole-2-thione-4,5-diselenolate) Showing an Unprecedented Anion Packing

The synthesis, X-ray structure, magnetic and transport properties of the compound Ni(dmf) 6[Ni(dsit) 2] 2 (dmf=dimethylformamide, dsit=1,3-dithiole-2-thione-4,5-diselenolate) are described. This compound crystallizes in the monoclinic space group P2 1/c, with a=18.709(6), b=22.975(5), c=20.418(5) Å, β=99.31(2)° and Z=6; its structure consists of [Ni(dsit) 2] 2 2− dimers and isolated [Ni(dmf) 6] 2+ cations both centrosymmetric and non-centrosymmetric. The dimers are packed forming chains along the [101] direction with short Se·Se interdimer contacts. Additional interchains S·S contacts render this structure a three-dimensional character, never observed so far in other [Ni(dsit) 2] − salts. This compound exhibits semiconducting behavior with a room temperature conductivity (1 S cm −1) much higher than those reported for other salts of the [Ni(dsit) 2] − anion. Tight-binding band structure calculations were used to analyze the origin of the semiconducting properties of this salt. The magnetic susceptibility shows Curie behavior with C=1.25 emu K mol −1, typical of isolated Ni(II) ions as expected for the octahedrally coordinated [Ni(dmf) 6] 2+ cations.