Resonance Raman spectroscopy and density functional theory calculation study of photodecay dynamics of tetra(4-carboxyphenyl) porphyrin

摘要

The 397.9 nm, 416.0 nm and 435.7 nm resonance Raman spectra were acquired for meso-tetrakis(4-carboxyphenyl)porphyrin (TCPP) in tetrahydrofuran solution, and the Raman effect of relaxation dynamics was analyzed according to Herzberg-Teller (vibronic coupling) contributions. Density functional calculations were done to help the elucidation of the Soret (B_x and B_y-band) electronic transitions and the corresponding photo relaxation dynamics of TCPP. The spectra indicate that the Franck-Condon region photo relaxation dynamics upon S0 → S4 electronic transition are predominantly along the totally symmetric C_m-ph stretch and Porphin ring breath stretch, and simultaneously along the asymmetric v(C_m-Phenyl) + δ(N-H) and v(C_α-C_m-C_α)_(as) + def (pyr) vibrational relaxation processes. The excited state structural dynamics of TCPP determined from the resonance Raman spectra show that the internal conversion between the B_y and B_x electronic states occurs in tens of femtoseconds, and the electronic relaxation dynamics were firstly interpreted taking into account the time-dependent wave packet theory and Herzberg-Teller (vibronic coupling) contributions.