Spectroscopic analysis of 2-mercaptobenzothiazole charge-transfer compounds with chloranilic acid and chloranil: morphological characterization, magnetic properties, and DFT investigations

Abstract

This study investigates the charge-transfer (CT) complexes formed between 2-mercaptobenzothiazole (MBT) as the electron donor and chloranilic acid (CHA) and chloranil (CHL) as electron acceptors, using spectrophotometric analysis in ethanol. UV–Vis spectroscopy revealed distinct absorption maxima at 292 nm and 291 nm for the MBT: CHA and MBT: CHL complexes, respectively, providing confirmation of charge-transfer (CT) complex formation. The key parameters such as the molar extinction coefficient (Ɛ_CT), formation constant (k_CT), oscillator strength (ƒ), transition dipole moment (μ_EN), ionization potential (I_P), and resonance energy (R_N) were calculated. Morphological and structural analysis using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the CT complexes form nanoparticles with sizes ranging from several tens of nanometers to a few micrometers. X-ray diffraction (XRD) confirmed the crystalline nature of these complexes. Magnetic properties assessed using a vibrating sample magnetometer (VSM) exhibited S-shaped hysteresis loops with weak magnetization and high coercivity, indicating ferromagnetic properties. Antimicrobial efficacy tests demonstrated significant activity against various microorganisms, including gram-positive and gram-negative bacteria, yeasts, and fungi. The minimal inhibitory concentration (MIC) tests specifically emphasized the strong antimicrobial activity of the MBT-CHA complex. Density functional theory (DFT) calculations offered valuable insights into the geometrical configurations, interaction energies, and electronic properties of the complexes, revealing robust charge-transfer (CT) interactions that aligned closely with the experimental findings. The detailed analysis indicates promising applications for these CT complexes in antimicrobial agents, materials science, and electronic devices.