EXPERIMENTAL-EVIDENCE OF THE SYMMETRY BREAKDOWN IN '-DITHIOL-2'-YLIDENE)-1,3,5,7-TETRATHIA-S-INDACENE COMPOUNDS

The visible-near-IR absorption spectra of a bis(TTF) molecule, 3'-dith iol-2'ylidene)-1,3,5,7-tetrathia-s-indacene (1), and of the correspond ing monocationic species 1(.+) generated by chemical or electrochemica l oxidation are reported. IR and Raman studies of 1 and the derived 1( x)PF(6) salt and ESR studies of 1(.+) are described. The results of th is experimental investigation are compared with those of semiempirical calculations performed using the PM3 or AM1 modeling and simulation p rograms, and of a normal coordinate analysis. This comparison affords additional evidence for a symmetry breakdown in radical cations based on such Ms(TTF) systems. An asymmetrical spin density distribution in the 1(.+) radical cation is also confirmed by ESR measurements.