SPECTROSCOPIC INVESTIGATION OF THE SYMMETRY BREAKDOWN IN BIS-TTF COMPOUNDS

The Vis-near IR absorption spectra of a bis-TTF molecule, zo-1',3'-dit hiolyden)-1,3,5,7-teteratia-s-indacene (I) and of the monocationic spe cies (I)(+) generated by chemical or electrochemical oxidation are rep orted. The IR and Raman studies of(I) and the derived (I)(x)PF6 salt, as well as the ESR studies of (I)(+) are described. The experimental r esults are compared with those of PM3 semiempirical calculations. This comparison provides' additional evidence for a symmetry breakdown in radical cations based on such bis-TTF systems. An asymmetric spin dens ity distribution in tile (I)(+) radical cation is also confirmed by th e ESR measurements.