Corrole-phenothiazine and porphyrin-phenothiazine dyads connected at β-position: Synthesis and photophysical properties

Two novel donor-acceptor dyads, in which phenothiazine (PTZ) connected at beta-pyrrolic position of either freebase corrole (TPC) or freebase porphyrin (TPP) via vinylic spacer have been synthesized. Both the dyads were characterized by ESI-MS, IR, H-1 NMR (10 and 2D H-1-H-1 COSY and J-Resolved), UV-Vis, Study state Fluorescence, Time-resolved fluorescence (Time-correlated single photon counting (TCSPC), Streak Camera) as well as electrochemical methods. In the absorption spectra of the dyads, both Soret and Q bands were red shifted by 8-20 nm indicating weak electronic communication between the two chromophores. However, the fluorescence emission from the PIZ of the dyad was efficiently quenched (96-99%) as compared to pristine PTZ where the dyad was excited at 310 nm, which is attributed to singlet-singlet excited energy transfer. Fluorescence emission from porphyrin part of the TPP-VIZ dyad also quenched when excite the dyad at 420 nm, which is ascribed to photoinduced electron transfer from ground state of VIZ to excited state of porphyrin. In contrast, when excite the corrole at 420 nm in TPCPTZ dyad, we found there are no significant changes in photophysical properties. In both the cases the solvent dependence of the rate of energy and electron transfer was observed. (C) 2017 Elsevier Ltd. All rights reserved.