Experimental investigations by using electrochemical, steady state and time resolved spectroscopic tools on the photoreactions of disubstituted indoles in presence of tetracyanoquinodimethane (TCNQ) and a theoretical approach by using time-dependent densi

The spectroscopic and photophysical properties of some dimethylindoles, 1,2-dimethylindole (12DMI) and 2,3-dimethylindole (23DMI) were measured in presence of electron acceptor, tetracyanoquinodimethane (TCNQ) in solvents of varying polarity by using electrochemical, steady state and time resolved spectroscopic techniques. Both from the theoretical considerations made by using time-dependent density functional theory (TD-DFT) and steady state polarization spectral measurements, it reveals the possibility of mixing of the two closely lying lowest electronic excited states 1La (S2) and 1Lb (S1) of DMIs. Though Stern–Volmer (SV) analysis of steady state measurements is unable to provide the information on the concurrent occurrences of static and dynamic processes involved, but electrochemical measurements coupled with time resolved spectroscopic investigations demonstrate that TCNQ may act as a potential electron acceptor in presence of dimethylindoles to undergo highly exergonic photoinduced electron transfer reactions in Marcus inverted region. Possibility of building up of various artificial or model photoactive systems with the linked DMI–TCNQ dyad systems is hinted at.