Studies on Ni(II), Cu(II) and Zn(II) complexes with 2-aminobenzamide and some bioactive imidazole enzyme constituents

A series of Ni(II), Cu(II), and Zn(II) complexes of 2-aminobenzamide(2AB : L) and some imidazole enzyme constituents(B) viz., imidazole(him), benzimidazole(bim), histamine(hist), and L-histidine(his) have been synthesized and characterized using analytical and various spectral studies. Vibrational spectral data of the synthesized complexes reveal that the ligands bind with metal(II) ions through nitrogen and oxygen. The calculated g-tensor values of Cu(II) complexes suggest that the unpaired electron is localized in the orbital. The results obtained from the spectral studies confirm the distorted octahedral environment around the metal(II) ions. Their powder XRD indicates microcrystalline nature and SEM pictographs identify their uniform surface morphology. Cu(II) and Ni(II) complexes show biological, antioxidant, and DNA activities when compared to free 2-aminobenzamide. Equilibrium studies have been carried out pH-metrically in 50% (v/v) water–ethanol mixture at 37 °C and I = 0.15 mol dm⁻³ NaClO₄. Analysis reveals the presence of certain heteroligand species viz., MLBH/MLB/MLB₂, in addition to various primary species. In MLB/MLB₂ species, 2AB(L) binds with M(II) ions via N-amino and O-amido, whereas the ligands(B) him and bim are monodentate, hist and his are bi and tridentate, respectively. The stabilization parameters Δ log K, log X, log X′, and % RS clearly indicate all the heteroligand complexes have higher stabilities than their primary.