Synthesis, spectroscopic and spectrophotometric studies of charge transfer complex of the donor 3,4-diaminotoluene with π-acceptor 2,3-dichloro-5,6-dicyano-p-benzoquinone in different polar solvents

The complexation of donor 3,4-diaminotoluene (DAT) with π acceptor 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) has been studied spectroscopically and spectrophotometrically in various polar solvents such as methylene chloride, ethanol, methanol and acetonitrile at room temperature, and their absorption spectra in solution were recorded. The results indicate that the complexation between donor and acceptor increases with a decrease in polarity of the solvents. The stoichiometry of the CT complex was established 1:1 using the straight line method with maximum absorption bands. The absorption regions of the CT bands were remarkably different from those of donor and acceptor. The novel CT complex has been characterized by FTIR, TGA-DTA, powder XRD, 1H NMR and 13C NMR spectroscopic techniques. The Benesi-Hildebrand equation has been used to determine the various important parameters such as formation constant (KCT), molar extinction coefficient (εCT), and Standard Gibbs free energy (ΔG°), oscillator strength (f), transition dipole moment (μEN), resonance energy (RN) and ionization potential (ID) of the CT complex in different polar solvents. Variations in thermodynamic parameters were observed to change in concentration of the acceptor and polarity of the solvent. Minimum and maximum absorbance method has been applied to estimate the formation constant of the CT complex where it recorded large value confirming its high stability.