We report a resonance Raman study on free-base tetraphenylporphine (H 2 TPP) and its chemically prepared diacid dispersed in polymethylcyanoacrylate (PMCA). Photoexcitation of the neutral porphine by laser light leads irreversibly to the formation of the diacid, with the p-cation radical as intermediate species.Resonance Raman (RR) spectra of the diacid dispersed in the polymer obtained with 441.6 nm in the wavenumber region of 100-1650 cm −1 are recorded. Wavenumbers with other excitation lines are also reported for the diacid species. Some bands assigned to out-of-plane vibrational modes and forbidden under ideal D 2h symmetry are also observed in the resonance Raman spectra of the diacid. These bands arise from the out-of-plane distortions, which reduce the symmetry of the molecule. These findings are supported by the electronic absorption studies of the diacid in the polymer.
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