SYNTHESIS AND CHARACTERIZATION OF COPPER (II) COMPLEX WITH SCHIFF BASE DRIVE FROM SALICYLALDEHYDE AND ANILINE

This research investigates the synthesis, coordination behavior, and physicochemical characterization of a Cu(II) complex derived from the Schiff base ligand obtained via the condensation of salicylaldehyde and aniline. The ligand, N-salicylideneaniline, was synthesized through a mechanochemically assisted solvent-free approach and subsequently coordinated to Cu(II) using CuSO₄ under reflux conditions. The Schiff base was obtained as a pale-yellow crystalline solid with a 76.60% yield, while the resulting Cu(II) complex formed as a dark-green solid with a 38.46% yield, reflecting typical chelation tendencies observed in N,O-donor ligands. Physicochemical analyses revealed significant differences between the free ligand and the metal complex. Solubility profiling showed that complexation reduced solubility in common organic solvents, consistent with increased lattice rigidity and chelation. FT-IR spectroscopy confirmed coordination via the azomethine nitrogen and phenolic oxygen, evidenced by the shift of the ν(C=N) band from 1643 to 1640 cm⁻¹ and the disappearance/downshift of the phenolic ν(O–H) band. The emergence of new metal-ligand vibrational bands ν(Cu–N) at 752.9 cm⁻¹ and ν(Cu–O) at 678 cm⁻¹—further validated bidentate coordination. Melting point analyses indicated enhanced thermal stability of the copper complex relative to the free ligand. Therefore, the results confirm the successful formation of a Cu(II) Schiff base complex with distinct structural and spectroscopic features attributable to chelation.