Time-resolved resonance Raman spectra of free-base tetraarylporphyrins: effects of the peripheral substituents

Time-resolved resonance Raman spectra of free-base tetraarylporphyrins were obtained to investigate the peripheral substituent effect on the structural changes in the excited states. The aryl mode of H2-tetratoluylporphyrin in the excited triplet state was more strongly enhanced relative to that of H2-tetramesitylporphyrin. These results are discussed in terms of the difference in the steric hindrance inhibiting the electron delocalization of the porphyrin in the excited states.