Resonance Raman enhancement of Fe-IV=O stretch in high-valent iron porphyrins: An insight from TD-DFT calculations

摘要

Density functional theory (DFT) has been applied to explain the origin of resonance Raman enhancement associated with the Fe-IV=O stretch observed in iron(IV)oxo porphyrins. To accomplish this electronic excitations of the Im-(Por)Fe-IV=O model were computed in the 1.5-4.0 eV spectral range using time-dependent DFT (TD-DFT). All electronic transitions having dominant pi -> pi* character were analyzed and assigned in terms of one-electron excitations. It was found that the most intense Soret band has a multicomponent character, but the pi (a(2u)) -> pi*(d(xv), d(yz)) and pi(a(1u)) -> pi*(d(xz), d(yz)) electronic excitations are primarily responsible for observed resonance enhancement of the Fe-IV=O stretch. (c) 2006 Elsevier Inc. All rights reserved.