Excited State Structural Dynamics of Tetra(4-aminophenyl)porphine in the Condensed Phase: Resonance Raman Spectroscopy and Density Functional Theory Calculation Study

Abstract

Resonance Raman spectra (RRs) of tetra(4-aminophenyl) porphine (TAPP) were obtained, and density functional calculations were done to help the elucidation of the photorelaxation dynamics of Soret (Bx and By band) and Qy electronic transitions. The RRs indicate that the photorelaxation dynamics for the S0 → S3 excited electronic state is predominantly along the totally symmetric porphin ring CβCβ + CmCα stretch, Cm−ph stretch, and simultaneously along the asymmetric ν(CmCα)as and ν(CαCβ)as relaxation processes leading to Qy while that for S0 → S2 is predominantly along the porphin ring CβCβ + CmCα stretch and simultaneously along the asymmetric ν(CmCα)as + ν(CαCβ)as relaxation processes leading to thermal equilibrium in Qx. The excited state structural dynamics of TAPP determined from RRs shows that internal conversion Bx → Qy electronic relaxation occurs in tens of femtoseconds and the short-time dynamics were first interpreted with account of the time-dependent wave packet theory and Herzberg−Teller contributions