Intramolecular photoinduced reactions in corrole–pyrene and corrole–fluorene dyad systems

We have designed and synthesized donor–acceptor conjugates in which donor polycyclic aromatic hydrocarbons such as either pyrene or fluorene linked at the pyrrole-β position of a corrole using vinylene spacer. Both the dyads are characterized by elemental analysis, MALDI-MS, 1H NMR, UV–vis and fluorescence spectroscopy (steady-state and time-resolved) as well as electrochemical method. The Soret absorption band of corrole was split in both the dyads and more over both Soret and Q bands are red-shifted by 15–25 nm as compared to the unsubstituted corrole. Ground state properties indicate that there is a moderate π–π interactions in these dyad systems. However, fluorescence emission of polycyclic aromatic hydrocarbons of both the dyads quenched significantly (88–98%) compared to their monomeric units. The quenched emission was attributed in terms of intramolecular excitation energy transfer, which competes with the photoinduced electron transfer reaction in these dyads.