Spectrophotometric and Spectroscopic studies of charge transfer complexes of Benzamide as an electron donor with Picric acid as an electron acceptor in different polar solvents

The charge transfer complexes of the donor benzamide (BZ) with π-acceptor picric acid (PA) have been studied spectrophotometrically in various solvents such as carbon tetra chloride, ethanol, and methanol at room temperature using absorption spectrophotometer. The results indicate that formation of CTC in less polar solvent is high. The stoichiometry of the CT complex was found to be 1:1. The physical parameters of CT complex were evaluated by the Benesi–Hildebrand equation. The data are discussed in terms of formation constant (K_CT), molar extinction coefficient (ε_CT), standard free energy (ΔG⁰), oscillator strength (ƒ), transition dipole moment (μ_EN), resonance energy (R_N) and ionization potential (I_D). The results indicate that the formation constant (K_CT) for the complex were shown to be dependent upon the nature of electron acceptor, donor and polarity of solvents which were used. The results show that a charge transfer molecular complex between picric acid and benzamide stabilized by hydrogen bonding. The formation of the complex has been confirmed by UV-visible, FT-IR, ¹H–NMR, TGA/DTA spectral data methods. On the basis of the studies, the structure of CT complex is [(BZ)⁺ (PA)⁻], and a general mechanism for its formation is proposed.