Synthesis, Spectral Characterization, and Antimicrobial Evaluation of Yb(III) Complex with 4-Hydroxyquinoline-2-carboxylic Acid

A novel ytterbium(III) complex with 4-hydroxyquinoline-2-carboxylic acid (kynurenic acid) was synthesized and characterized using elemental analysis, FT–IR, UV–Visible spectroscopy, thermogravimetric analysis (TGA), and mass spectrometry. Spectral data confirmed the coordination of the ligand in a bidentate O,O′ mode via carboxylate and phenolic oxygen atoms, forming a neutral complex of the type [Yb(L)₃(H₂O)₂]. Thermal analysis revealed the presence of coordinated water molecules and high thermal stability of the complex. The antimicrobial activity of the complex was evaluated against selected bacterial and fungal strains, showing enhanced activity compared to the free ligand. The results suggest that metal coordination significantly improves biological efficacy, highlighting the potential of quinoline-based lanthanide complexes as antimicrobial agents.