FLUORESCENCE DECAY KINETICS AND STRUCTURE OF AGGREGATED TETRAKIS(P-SULFONATOPHENYL)PORPHYRIN

Fluorescence decay dynamics and structure of a meso-tetrakis(p-sulfona tophenyl)porphyrin, referred to herein as either H2TSPP4- or TSPP, whi ch aggregates in highly acidic homogeneous solution, are discussed. Th e fluorescence Lifetime of the aggregate is found to depend on whether electronic excitation is to the B (Sorer) slate or the Q state. This finding is interpreted as indicating that the aggregate's effective si ze differs in the two cases. Also, a discussion is provided of possibl e nonradiative pathways that might affect measured fluorescence lifeti mes. Specific structural changes that occur within the porphyrin upon N-protonation and incorporation within the aggregate are also discusse d. Additionally, vibrational frequencies are assigned to specific bond s of the porphinato macrocycle, and comparisons are made between bond lengths in the aggregate environment and those of the monomeric dianio n.