Synthesis and Characterization of Metal Complexes Derived from 3-Hydroxy-2-methyl-4-pyrone and phthalic acid

This work reports the aqueous-phase synthesis and physicochemical characterization of a series of complexes utilizing Cu²⁺, Sn²⁺, Hg²⁺, and Ag⁺ metal centers with the oxygen-based ligands 3-hydroxy-2-methyl-4-pyrone and 1,2-benzenedicarboxylic acid, aiming to map their thermal stabilities, structural phases, and coordination modes for potential catalytic and biomedical applications. For the maltol-based derivatives, stoichiometric amounts of the respective metal salts, NaOH, and maltol were stirred at 50°C for 30 minutes, followed by crystallizationFTIR spectra confirmed ligand deprotonation and metal coordination in all samples. In the maltol complexes, the pro-ligand's -OH band disappeared and the C=O stretching vibration shifted to lower frequencies, confirming chelation. For the phthalate structures, the carboxylic C=O band split into asymmetric (_νassCOO⁻) and symmetric (_νsimCOO⁻) vibrations. The Δν parameter indicated bridging bidentate modes for the Sn2+ and Ag⁺ complexes and a monodentate mode for the Hg²⁺ complex.