The crystal and electronic structure analysis of (OMTTF)(2)[Ni(tdas)(2)]

The crystal structure of (OMTTF)(2)[Ni(tdas)(2)] (OMTTF=octamethylenetetrat hiafulvalene 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 de rivatives. The structure consists of a dimer of the radical cation of the O MTTF 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 cha rge-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(td as)(2)] are significantly large in the HOMO of the dianion, the packing mot if of this complex prohibited the formation of a three-dimensional network of intermolecular interactions. Also, a peculiarity of the energy diagram o f the molecular orbitals (MO) of Was is discussed on the basis of semiempir ical MO calculations.