Synthesis, Characterization, and Antibacterial Activity of Anion-Depended Cu(II)-Niacinamide Complexes

Abstract

This study aims to prepare different types of Cu(II)-niacinamide complexes by layered solution method from various sources of Cu(II) salts (sulphate, nitrate, chloride, and acetate) and in various M(II):niacinamide molar ratio (1:2, 1:4, and 1:6). The antibacterial activities of those complexes were also explored. The complexes were characterized by infrared spectroscopy, melting point test, powder-XRD, anion qualitative test, and scanning electron microscopy. Experimental data reveal that anion of the Cu(II) affects the crystallization of Cu(II)-niacinamide complex, in which various shapes and types of solid products were formed, namely light blue hair-like crystals (sulphate), dark green block crystals (acetate), and turquoise sword-like microcrystalline (chloride). These three anions act either as a free ions in the crystal lattice (chloride) or as ligands (sulphate and acetate). Based on the characterization, the crystals obtained from the sulfate, chloride, and acetate reactions were predicted to be complexes of [Cu(L)x(SO₄)], [Cu(L)x]Cl₂, and [Cu₂(L)₄(CH₃COO)₂], respectively, where L = niacinamide. Antibacterial test of the three complexes toward E. coli and S. aureus shows that the complexes have better activity than the free niacinamide.