SPECTROELECTROCHEMISTRY AND RESONANCE RAMAN SPECTRA OF VANADIUM(II) AND (III) COMPLEXES OF 2, 2 -BIPYRIDINE

The optical and redox properties of the [V(bipy) 3 ] 2 + and [V 2 0(bipy) 4 CI 2 ] 2+ complexes (bipy = 2, 2′-bipyridine) were studied by resonance Raman and spectroelectrochemical techniques. Strong enhancement of the vibrational modes of bipy was observed in the Raman spectra of the [V(bipy) 3 ] 2 + complex. In contrast, the Raman spectra of [V 2 0(bipy) 4 Cl 2 ] 2 + exhibited pronounced enhancement of the vibrational modes of the V(III)-0-V(III) chromophore. Spectroelectrochemical measurements carried out for the [V(bipy)] 2 + complexes showed that for n = 1 and 2, the oxidation process leads to oxo-bridged binuclear V(III) species, and for n = 3, the oxidation proceeds viatwo successive electron transfer steps, generating vanadium(IV) products.