Multifunctional Mercury and Uranyl Complexes of Thiosemicarbazone Ligand for Bioinorganic Innovation

This study reports the synthesis and comprehensive characterization of novel metal complexes formed by coordinating a custom-designed thiosemicarbazone ligand with mercury(II) and uranium(VI) oxide ions. Structural and electronic properties were elucidated using elemental analysis, FT-IR, UV-Vis, 1H NMR spectroscopy, and density functional theory (DFT) calculations. Spectroscopic data revealed that the ligand acts as an NS-bidentate donor in the Hg(II) complex and as an NNS-tridentate donor in the U(VI)O2 complex. UV-Vis analysis confirmed ligand-to-metal charge transfer (LMCT) transitions, supporting the proposed geometries, while DFT-based molecular orbital analysis provided insights into electronic distribution and chemical reactivity. Geometry optimization suggested a tetrahedral arrangement around the Hg(II) center. Biological evaluation was conducted using the disk diffusion method for antimicrobial activity and the DPPH radical scavenging assay for antioxidant potential. Biological screening demonstrated moderate antimicrobial activity, particularly against Staphylococcus aureus and Bacillus cereus, alongside notable antioxidant potential, with an IC50 value of 0.047 mg/mL. These findings highlight the dual bioactivity and structural integrity of the synthesized complexes, suggesting their potential for future applications in therapeutics, sensing technologies, and catalysis.