Triphenylamine–Corrole Donor–Acceptor Systems: Synthesis, Spectroscopy, and Photophysical Studies!

Donor-Acceptor (D-A) systems in which a triphenylamine has tethered at meso phenyl position of corrole (1-TPA-Cor) corrole monomer, (2-TPA-Cor) corrole dimer, and (3-TPA-Cor) corrole trimer have been designed and synthesized. All three D-A systems have been characterized by various spectroscopic techniques that include 1H NMR, 13C NMR, HR -MS, absorption, and emission (both steady-state and lifetime) spectroscopies as well as electrochemical methods. Optical and theoretical studies suggest that there will be π-π interactions between donor triphenylamine (TPA) and acceptor corrole (Cor) units and as a result both Soret and Q-bands are red-shifted with broadening of Soret band. Selective excitation of TPA in these D-A systems at 300 nm resulted in the quenching of TPA emission suggested the photo-induced electron transfer (PET) from 1TPA* to corrole. In contrast, excited at 405 nm also resulted in quenching of emission of Cor. As the number of corrole units and polarity of the solvent increased the quenching is more and suggested that PET reactions in these D-A systems. Time-resolved fluorescence studies shown the presence of PET within these systems and revealed an ultra-fast electron rate of ∼108 to 1010 s-1, follows the order 3-TPA-Cor > 2-TPA-Cor > 1-TPA-Cor and are polarity of solvent dependent.