New 1:3 type nickel-bis(dithiolene) salt (FcCHCHPymCH3)[Ni(dmit) 2]3 (dmit: 2-thioxo-1,3-dithiole-4,5-dithiolate): Its electrocrystallization, crystal structure, electrical properties, and electronic band structure analysis

Abstract

Black single crystals of Ni(dmit)2 complex (dmit: 2-thioxo-1,3-dithiole-4,5-dithiolate) with trans-4-[2-(1-ferrocenyl)-vinyl]-1- methylpyridinium chromophore as a countercation, (FcCHCHPymCH 3)[Ni(dmit)2]3, were prepared by the electrocrystallization technique. In the triclinic structure of the complex (P1, a = 11.430(5) Å, b = 13.349(2) Å, c = 19.355(6) Å, α = 75.15(2)°, β = 79.19(3)°, γ = 82.12(2)°, Z = 2), Ni(dmit)2 anion layers are separated by the cations with a relatively rare 1:3 cation-to-anion ratio. Detailed crystal and electronic structure analysis revealed that the anions are stacked in the layers to form alternating dimers and monomers rather than trimers. The measured electrical conductivity indicates a semiconducting property of the compound with an estimated energy gap of 0.06 eV. The calculated LUMO bands are very narrow, and the semiconducting behavior is more likely due to the electron localization mainly on the dimers, consistent with the observed longer Ni-S bond distances in the dimers.