SYNTHESIS, SPECTROSCOPIC CHARACTERIZATION AND PROPERTIES OF IMIDAZOLE-COPPER (II) COMPLEX

This study focuses on the synthesis, characterization, and analysis of the physical and spectroscopic properties of copper(II) complexes with imidazole ligands at varying ligand-to-metal ratios (1:1, 1:2, 1:3, and 1:4). The copper-imidazole complexes were synthesized using a solution-based reaction of copper(II) sulfate with imidazole, followed by purification and drying. Characterization techniques including UV-Visible spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) were employed to confirm complex formation and determine structural features. The percentage yield of the complexes increased from a 1:1 to 1:2 ratio but decreased at higher ligand ratios due to coordination saturation. UV-Vis spectra revealed characteristic d-d transitions and ligand-to-metal charge transfer (LMCT) bands, with peak shifts influenced by ligand concentration and coordination geometry. FTIR spectra displayed changes in N–H and C–N vibrations, confirming metal-ligand bonding through nitrogen atoms of imidazole. Notably, Cu–N stretching bands around 598 cm⁻¹ confirmed coordination. Melting point analysis indicated high thermal stability, with values ranging from 235°C to 243°C. Solubility tests showed the complexes were insoluble in common organic solvents but soluble in water under acidic conditions (pH 3.5), indicating pH-dependent behavior. The findings suggest that increasing copper concentration improves complex stability and coordination up to an optimal ratio (1:2), beyond which aggregation and decreased yield occur. These results confirm the successful synthesis of stable, thermally robust copper(II)-imidazole complexes and highlight their potential applications in coordination chemistry, materials science, and biologically active compound development.