RESONANCE RAMAN-SPECTROSCOPY OF BENZENEDITHIOLATE COMPLEXES - EVIDENCES OF EXTENSIVE DELOCALIZATION OF THE CHROMOPHORE

Resonant Raman spectra of the square planar complexes [Bu(4)N][M(dbt)( 2)] (M = Ni, Co, Cu; bdt = 1,2-benzenedithiolate; Bu = butyl) have bee n obtained with a variety of excitation lines. In all cases a strong b and at about 400 nm is now definitely assigned to a ligand-to-metal ch arge transfer (LMCT) transition on the basis of the observed pre-reson ance enhancement of modes assignable to the metal-sulphur chromophore. For the cobalt species, an additional strong band at about 670 nm is observed and is assigned to another CT transition on the basis of the enhancement of modes related to the C=C=S moiety, such proposal being supported by calculations based on the transform method.