Computational Study of Interfacial Charge-Transfer Complexes Between ZnO and Thiol Analogs of Catechol

Abstract

Interfacial charge-transfer (ICT) complexes provide an effective strategy for extending the optical absorption of wide-bandgap oxides into the visible spectrum, a key requirement for enhancing photo-driven reactions. In this work, density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were employed to investigate the ICT complexes formed between ZnO nanoparticles and benzene derivatives, specifically catechol (CAT), 2-mercaptophenol (2-MP), and 1,2-benzenedithiol (1,2-BDT). The results show that ZnO complexes with catechol and 2-mercaptophenol display ICT transitions in the visible region, whereas the 1,2-benzenedithiol complex primarily absorbs in the ultraviolet range. This behavior is attributed to differences in Zn─O and Zn─S bonding interactions, with sulfur-containing ligands forming stronger bonds. Nevertheless, the absorptions of 2-MP/ZnO and 1,2-BDT/ZnO are blue-shifted compared to the CAT/ZnO system. Further modifications, such as ligand substitutions, could be necessary to optimize absorption near the solar spectrum's peak. Therefore, a crucial aspect of this study is the assessment of two sulfur-containing analogs of catechol, a well-established ligand for use in ICT-based applications. © 2025 Wiley-VCH GmbH.