Photophysics of Soret-excited tetrapyrroles in solution. III. Porphyrin analogues: Aluminum and gallium corroles

Fluorescence from the second excited singlet states of two metallated corroles, Al(tpfc)(py) and Ga(tpfc)(py), has been observed for the first time. The excited state dynamics have been investigated using femtosecond fluorescence upconversion methods. The S2 excited states relax to the S1 states on a sub-picosecond time scale with quantum efficiencies in the 0.8–0.9 range. The radiative and nonradiative decay rate constants for the S2 states of these corroles are consistent with smaller transition moments for S2–S0 radiative decay and substantially increased radiationless transition rates compared with similar metalloporphyrins. The reasons for these differences are discussed.