Synthesis and Spectroscopic Characterization of Manganese-Theophylline-Dicarboxylic Acid Complexes

This study investigates the synthesis and characterization of manganese complexes of theophylline, a xanthine derivative with therapeutic relevance, using dicarboxylic acids such as isophthalic acid (ISO), oxalic acid (OXA), and terephthalic acid (TER) as auxiliary ligands. The complexes were synthesized via hydrothermal method and yielded distinct crystalline and powdery products. UV-Vis spectroscopic analysis revealed ligand transitions at 273–275 nm and ligand-to-metal charge transfer (LMCT) bands at 371–454 nm, indicative of metal-ligand interactions. FTIR spectroscopy confirmed the coordination of manganese ions with theophylline and dicarboxylic acids, evidenced by shifts in the N-H (~3100 cm⁻¹) and C=O (~1658 cm⁻¹) stretching vibrations, along with the emergence of new bands at 450–600 cm⁻¹, corresponding to Mn–O and Mn–N stretching. These findings underline the potential of manganese-theophylline-dicarboxylic acid complexes for biological and therapeutic applications.