Photocatalytic activity, DFT/ TD-DFT, and spectrophotometric studies of a synthesized charge transfer complex of p- toluidine with 1,2,4,5-benzenetetracarboxylic acid in various polar solvents

Abstract

The hydrogen bound charge transfer (CT) complex of p-toluidine (PT) and 1,2,4,5-benzenetetracarboxylic acid (BTC) was synthesized and subsequently characterized using a range of spectrum approaches such as FTIR, TGA / DTA, SC-XRD, and spectrophotometric examinations. Crystallographic evidence suggests that a strong hydrogen bond (N+____ H----O–) connects the cation and anion. This occurs when a proton is transported from the acceptor to the donor. The FTIR spectrum displays the proton transfer band, which is the region where neither the donor (PT) nor the acceptor (BTC) exhibits any absorption. A spectroscopic analysis showed that the CT complex (CTC) containing hydrogen bond has 1:1 stoichiometry. Benesi- Heildebrand equation was used for calculating the formation constant (KCT), molar extinction coefficient (ԑCT) and also to derive values for other physical parameters, such as energy of interaction (ECT), ionization potential (ID), free energy (ΔG°), resonance energy (RN) and oscillator strength (f). Thermal testing confirms that the newly synthesized CTC is stable at room temperature. DFT (Density Functional Theory) and TD-DFT (Time-Dependent Density Functional Theory) calculations at the B3LYP/6-311G++ level of theory were used to investigate the optimized geometry of the synthesized CTC and reactants (PT and BTC), with comparable theoretical data to support the experimental results. Furthermore, employing Hershfeld surfaces and the corresponding 2D fingerprint plots, the study of intermolecular interactions that maintain the crystal packing has been carried out. We also proved the CTC's efficiency as a photocatalyst for methylene blue (MB) breakdown, achieving 81 % photodegradation under UV–Vis light for 130 min. The scavenging analysis further demonstrates that holes and hydroxyl radicals are the photochemically active species responsible for dye particle disintegration.