Synthesis, Spectroscopic Characterisation and Application of Copper Complexes of Thiamine with Auxiliary Ligands: Urea and Phenanthroline

Abstract

Thiamine (vitamin B1) is an essential biomolecule with potential coordination sites capable of forming stable metal complexes, while auxiliary ligands can further enhance the structural and physicochemical properties of such systems. Copper-based thiamine complexes have attracted growing interest because of their potential applications in drug delivery, bioavailability enhancement, and biomedical research. This study investigates the synthesis and characterisation of copper complexes of thiamine with auxiliary ligands such as urea and phenanthroline. The complexes were synthesised via hydrothermal methods and yielded distinct powdery products. UV–Vis spectroscopic analysis revealed ligand transitions at 219–297 nm. FTIR spectroscopy confirmed the coordination of copper ions with thiamine and auxiliary ligands, evidenced by shifts in the C=C (~1557 cm⁻¹) and C=O (~1614 cm⁻¹) stretching vibrations, together with the appearance of new bands at 471–562 cm⁻¹ corresponding to Cu–O and Cu–N stretching modes. The synthesised copper complexes displayed improved stability, which may contribute to enhancing the pharmacokinetic profile of thiamine. These findings highlight the potential of copper–thiamine complexes containing auxiliary ligands for applications in controlled drug delivery and improved bioavailability. Further studies are underway to evaluate their biological activities and therapeutic potential.