Light induced intramolecular electron and energy transfer events in rigidly linked borondipyrromethene: Corrole Dyad

We have designed and synthesized a photo-induced energy/electron donor-acceptor conjugate comprising of corrole linked to BODIPY at the 5-position via ester linkage. The dyad was characterized by elemental analysis, MALDI-MS, UV-Visible, 1H NMR fluorescence spectroscopy (steady-state and time-resolved) as well as electrochemical methods. A comparison of the UV-visible and 1H NMR spectra of the dyad with those of the corresponding individual model compounds (i.e., BODIPY-CO2H and BPFC-OH) reveal that there exist minimum π-π interactions between BODIPY and corrole π-planes. Quenched emission of BODIPY and corrole part of the dyad has been observed in five different solvents. Excitation spectral data provided evidence for an intramolecular excitation energy transfer (EET) from the singlet BODIPY to the corrole and an intramolecular photoinduced electron transfer (PET) from singlet state of corrole to ground state of BODIPY. 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.