ABSORPTION AND RAMAN-SCATTERING BY AGGREGATED MESO-TETRAKIS(P-SULFONATOPHENYL)PORPHINE

In the present paper, we combine absorption and Raman scattering measurements to characterize aggregated TSPP in homogeneous aqueous solution. We deduce that aggregation evolves through the formation of TSPP diacid and that the diacid is the repeating unit in the aggregate. We further conclude that vibrations of adjacent molecules are perturbed in a fashion that is consistent with the pyrrolic ring in the porphinato macrocycle being ruffled, and that two aggregate arrangements occur: specifically, linear J- and H-type aggregate structures are proposed which are commonly defined in molecular exciton theory. Aggregation enhancement is advanced as a viable mechanism to explain enhanced Raman scattering, especially for homogeneous, aqueous phase TSPP, where SERS is not applicable. Vibrational band assignments are also made.