Electronic transitions of the manganate(V) ion in aqueous solution: at resonance Raman study

The resonance Raman spectra of manganate(V) ion in aqueous solution in the visible and near-UV regions were studied, The maximum in the Raman excitati on profile (REP) of the totally symmetric vibrational mode (v(1)) at ca 600 nm is assigned to a charge-transfer transition with appreciable d-d charac ter, Owing to marked orbital mixing in such systems, the observed Raman enh ancement could also be assigned to a d-d transition with a high charge-tran sfer character. The absence of overtones in the Raman spectrum indicates a small shift in the equilibrium Mn-O bond distances (delta(r)) between the e xcited and fundamental electronic states. This finding was confirmed by the calculation of the REP within the time formalism approach. The best fitted delta(r) value is lower than the corresponding reported values for mangana te(VII) and manganate(VI) ions. Two models were used in the calculations, i n which whether a single or two electronic transitions were considered in t he visible range of the absorption spectrum. Similar delta(r) values were o btained with both models. Copyright (C) 1999 John Wiley & Sons, Ltd.