ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Synthesis, spectroscopic, biological, and computational investigation of a hydrogen-bonded charge transfer complex of m-nitroaniline with oxalic acid in polar solve

Syed Khalid Mustafa, Meshari M. H. Aljohani, Omar M. Alatawi, Noha Omer, Rasha Jame, Adel D. Althaqafy, Khadra B. Alomari, Matiur Sk, and Maidul Islam

Department of Chemistry, Faculty of Science, University of Tabuk, Tabuk, Kingdom of Saudi Arabia

E-mail: aligmi111.chem@gmail.com

Received: 6 August 2025  Accepted: 26 January 2026

Abstract:

This work reports the synthesis, comprehensive characterization, and multidisciplinary evaluation of a HBCTC formed between m-NA and OA in ethanol. Structural confirmation was achieved through FTIR, UV–Vis spectroscopy, PXRD, TGA/DTA, NMR, and high-resolution mass spectrometry, all of which verified hydrogen bonding, proton transfer, and donor–acceptor charge-transfer interactions. Thermal analysis revealed high thermal stability, while PXRD showed a semi-crystalline framework with well-defined diffraction features. SEM micrographs displayed uniform needle-like structures confirming organized supramolecular assembly. Biological investigations demonstrated that the HBCTC exhibits significantly enhanced antibacterial and antifungal activities compared to its parent molecules, with pronounced concentration-dependent inhibition against E. coli, Bacillus subtilis, Staphylococcus aureus, Candida albicans, Fusarium oxysporum, and Aspergillus niger. The complex also showed superior antioxidant capacity relative to m-NA and OA. Fluorescence quenching studies revealed strong binding affinity toward lysozyme, indicating potential for biomolecular recognition and medicinal applications. Computational analysis using DFT and TD-DFT provided insight into the electronic architecture of the complex, revealing a reduced HOMO–LUMO band gap, strengthened charge-transfer characteristics, and distinct electronic transitions consistent with donor and acceptor behavior. Molecular docking further confirmed strong and favorable interactions between the HBCTC and lysozyme protease (1JKB), with a binding energy of − 190.59 kJ/mol. Collectively, the integrated experimental–theoretical findings highlight the HBCTC as a multifunctional material with promising potential in antimicrobial therapy, antioxidant applications, protein-binding studies, and future drug-design investigations.

Keywords: Spectrophotometric; Protein binding; Antimicrobial studies; Computational investigation

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04702-y

Chemical Papers 80 (4) 4429–4456 (2026)