Abstract

The crystal structure of (OMTTF)₂[Ni(tdas)₂] (OMTTF = octamethylenetetrathiafulvalene and tdas = 1,2,5-thiadiazole-3,4-dithiolate) was solved as the second example of an M(tdas)₂ (M = transition metal) complex with TTF derivatives. The structure consists of a dimer of the radical cation of the OMTTF molecules and the Ni(tdas)₂ dianion, which are located in the cation and anion sites in an NaCl-type structure, respectively. The degree of charge-transfer (CT) is determined from optical spectra, which are interpreted as the superposition of those of radical cation and the dianion. Although the atomic orbital (AO) coefficients of the terminal sulfur atoms of [Ni(tdas)₂] are significantly large in the HOMO of the dianion, the packing motif of this complex prohibited the formation of a three-dimensional network of intermolecular interactions. Also, a peculiarity of the energy diagram of the molecular orbitals (MO) of tdas is discussed on the basis of semiempirical MO calculations.