Photoinduced intramolecular reactions in triphenylamine–corrole dyads

• Donor triphenylamine (TPA) either directly connected to a corrole (Cor) acceptor (TPA-Cor) or separated by an ethynylphenyl bridge between TPA and Cor (TPA-E-Cor) have been designed for photophysical studies.
• No π–π interactions between triphenylamine and corrole π-planes in the ground state.
• Excited state properties indicate that there is an intramolecular energy transfer.
• Photoinduced processes are discussed by applying Forster and Dexter theories.

Donor–Acceptor systems, in which a donor triphenylamine (TPA) directly connected to a corrole (Cor) acceptor (TPA-Cor) and separated by an ethynylphenyl bridge between TPA and Cor (TPA-E-Cor) have been designed, synthesized and fully characterized by elemental analysis, MALDI-MS, UV–Visible and 1H NMR spectroscopic methods. A comparison of the UV–Visible and 1H NMR features of these D–A systems with those of the corresponding individual model compounds (i.e., TPA and Cor) reveal that there exist minimum π–π interactions between triphenylamine and corrole π-planes. Quenched emission of triphenylamine (but not corrole) part of both the dyads have been observed in three different solvents. Excitation spectral data provides evidence for an intramolecular excitation energy transfer (EET) from the singlet triphenylamine to the corrole. Detailed analysis of the data suggests that Forster’s dipole–dipole mechanism does not adequately explain this energy transfer but, an electron exchange mediated mechanism can, in principle, contribute to the intramolecular EET.

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