Benzothiazole Functionalized Corrole Based Donor-Acceptor Dyads: Synthesis, Photophysical Studies, and Investigating the Role of Benzothiazole in Light Induced Events.

A series of benzothiazole (BTZ) functionalized corrole (Cor) based donor-acceptor systems, Dyad-1, Dyad-2, and Dyad-3, with varied spacers, namely phenyl, biphenyl, and ethoxyphenyl respectively, were synthesized and the photoinduced energy transfer (PEnT) and electron transfer (PET) events were explored. Optical absorption studies have revealed negligible ground-state electronic interactions between the two chromophores. Steady-state fluorescence studies performed by selectively exciting the BTZ unit at 305 nm revealed a pronounced quenching of the BTZ emission, accompanied by the emergence of the corrole fluorescence indicating the occurrence of the PEnT from 1BTZ* to corrole. However, when the corrole moiety of dyads is excited at 410 nm, the emission is not quenched and found comparable with the emission intensity of the control compound, Ph-Cor, indicating that PEnT is the major photophysical pathway responsible for the quenching of BTZ emission. The electrochemical studies have shown that the first oxidation and reduction are results of the corrole moiety, corroborating with the computational results, implying that the occurrence of the PET is minimal in these dyads. Parallel lifetime measurements of the dyads have displayed a bi-exponential decay for the BTZ emission, but an unquenched corrole excited state, supporting the occurrence of the PEnT in these dyads.