Investigation of Gallium(III) Complexes with Thiouracil Derivatives: Effects of pH on Coordination and Stability

Abstract

This study explores the formation and properties of new complexes involving gallium(III) and thiouracil derivatives—2-thiouracil (TU), 6-methyl-2-thiouracil (MTU), 6-propyl-2-thiouracil (PTU), 5-carboxy-2-thiouracil (CTU), and 6-methoxymethyl-2-thiouracil (MMTU). Conducted in aqueous solutions at relatively low concentrations, this research enabled the formation of soluble complexes, identified and described here for the first time. The influence of metal-to-ligand ratios on species distribution and their fluorescence properties was examined through potentiometric titration, alongside visible and fluorescence spectroscopy. Stability constants were determined, revealing that coordination mode and complex stability are pH-dependent, and nitrogen, sulfur, and oxygen atoms are involved in higher pH coordination. Additionally, the structure of the ligand 6-methoxymethyl-2-thiouracil was characterized. The findings suggest that these complexes hold potential for future biomedical applications, particularly as antibacterial and anticancer agents, warranting further studies under physiological conditions.