Photodecay dynamics of octaethylporphine in the condensed phase explored via resonance Raman spectroscopy and density functional theory calculation

Abstract

Resonance Raman spectra of free-base octaethylporphine (OEP) were obtained with 368.9 nm, 397.9 nm and 416.0 nm excitation wavelengths, and density functional calculations were done to help the elucidation of Soret ( B x and B y -band) electronic transitions and the corresponding photo relaxation dynamics of OEP. The RRs indicate that the Franck–Condon region photo relaxation dynamics upon S 0 → S 8 eletronic transition is predominantly along the totally symmetric C mC α stretch, the C βC β stretch, and simultaneously along the asymmetric δ(pyr deformation), γ(CH 2) vibrational relaxation processes. The excited state structural dynamics of OEP determined from resonance Raman spectra show that the internal conversion between B y and B x electronic states occurs in tens of femtoseconds and the electronic relaxation dynamics were firstly interpreted with account of the time-dependent wave packet theory and Herzberg–Teller (vibronic coupling) contributions.