Synthesis, spectroscopic, and computational studies of charge-transfer complexation between benzidine with 2,3-dichloro-5,6-dicyano-p-benzoquinone and chloronil

The solid charge transfer (CT) complexes that have been formed from the reactions of donor benzidine (BZ) and the π-acceptors such as 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and chloronil (CHL) have been studied and characterized experimentally and theoretically. The experimental work which includes the use of UV-visible spectroscopy to identify the CT band of the CT-complex. The composition of the complexes has been investigated successfully by using spectrophotometric titration and Job method of continuous variation to be 1:1. Furthermore, to calculate the formation constant and molar extinction coefficient, we have used the Benesi-Hildebrand equation. Infrared and proton nuclear magnetic resonance spectral studies were used to characterize and confirm the formation of CT-complex. The experimental studies were well supported by quantum chemical simulations by using density functional theory. The computational analysis of molecular geometry, Mulliken charges, and molecular electrostatic potential surfaces of reactants and complexes is very much helpful in assigning the CT route. The C═O bond length of DDQ and CHL increased upon complexation with BZ. We have also observed that the substantial amount of charge has been transferred from BZ to DDQ and CHL in the process of complexation. An excellent consistency has been achieved between experimental and theoretical results.