Light induced intramolecular energy and electron transfer events in carbazole-corrole and phenothiazine-corrole dyads

We report two corrole based donor-acceptor (D-A) dyads, Cbz-Cor and Ptz-Cor to understand the energy/electron transfer reactions. In these D-A systems, the donor, either carbazole (Cbz) or phenothiazine (Ptz), is covalently connected at the meso-phenyl position of 10-(pheny1)-5,15-bis-(pentafluorophenyl)corrole (Ph-Cor) by C-N linkage. Both the dyads were characterized by H-1 NMR, MALDI-TOF MS, UV-vis, electrochemical, computational methods, study state fluorescence and TCSPC techniques. A comparison of absorption spectra with their reference monomeric compounds (Cbz-Ph, Ptz-Ph and Ph-Cor) revealed minimal ground-state interactions between chromophores in both dyads. fluorescence studies suggested that singlet-singlet energy transfer from (1)Cbz* to corrole is the major photochemical pathway in the Cbz-Cor dyad with a quenching efficiency of similar to 99%. Detailed analysis of the data suggests that Forster's dipole-dipole mechanism does not adequately explain this energy transfer. However, at a 410 nm excitation, florescence quenching is detected in Ptz-Cor (49%) supporting a photo induced electron transfer (PET) process from the ground state of vrz to the excited state of corrole macrocycle. The electron-transfer rates (k(ET)) of Ptz-Cor are found in the range 0.6 x 10(7) to 1.24 x 10(8) s(-1) and are concluded to be solvent dependent.