Resonance Raman spectra of manganese (III) etioporphyrin I

Resonance Raman spectra of manganese (III) etioporphyrin I complexes have been obtained with laser excitation in the regions of the bands III and IV, and bands V and V_a of the atypical visible absorption spectra of these metalloporphyrins. Excitation profiles in the latter region are interpreted as indicating nonadiabatic coupling between V and V_a as well as vibronic activity of some totally symmetric modes. The Raman data support assignment of bands III and IV to the 0-0 and 0-1 components of the Q band. Although bands V and V_a are assigned to a charge transfer transition mixed with the main π→π* transition, no selective enhancement of low frequency metal-ligand vibrations attributable to the charge transfer contribution of band V was observed.