Novel Ni(II) and Zn(II) complexes coordinated by 2-arylaminomethyl-1H- benzimidazole: Molecular structures, spectral, DFT studies and evaluation of biological activity

[NiL^1,2Cl₂(OH₂)₃] ·zH₂O and [ZnL^1,2(CH₃CO ₂)₂] (L¹ = (1H-benzimidazol-2-ylmethyl)-N- phenyl amine, z = 0 and L² = 2-[(1H-Benzimidazol-2-ylmethyl)-amino]- benzoic acid methyl ester, z = 1) complexes have been synthesized and characterized by a variety of physico-chemical techniques. The central Ni(II) ion is coordinated by only the pyridine-type nitrogen (N_py) of benzimidazole ring, three water molecules and two chlorido ligands forming a distorted octahedral geometry. Five coordinated zinc complexes were obtained, where the coordination sphere of zinc ion is made up of secondary amino group (NH_sec), N_py and two acetate groups, one acts as a unidentate and the other as a bidentate. A theoretical DFT/UB3LYP method combined with LANL2DZ basis set shows that all the metal-ligand bonds are of the L → M type. Electronic structures have been calculated using TD-DFT method. The antibacterial activity of NiL² complexes decreases by the introduction of COOCH₃ group in the ortho-position of the aniline moiety.