Polarized resonance Raman dispersion spectroscopy on metalporphyrins

Resonance Raman spectroscopy is an ideal tool to investigate the structural properties of chromophores embedded in complex (biological) environments. This holds particularly for metalporphyrins which serve as prosthetic group in various proteins. Resonance Raman dispersion spectroscopy involves the measurement of resonance excitation and depolarization ratios of a large nu mber of Raman lines at various excitation energies covering the spectral re gion of the chromophore's optical absorption bands. Thus, one obtains reson ance excitation profiles and the depolarization ratio dispersion of these b ands. While the former contains information about the structure of excited electronic states involved in the Raman scattering process, the latter refl ects asymmetric perturbations which lower the porphyrin macrocycle symmetry from ideal D-4h The article introduces and compares different quantum mech anical approaches designed to quantitatively analyze both resonance excitat ion and the relationship between symmetry lowering and depolarization ratio dispersion. Copyright (C) 2001 John Wiley & Sons, Ltd.