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

[NiL1,2Cl2(OH2)3]·zH2O and [ZnL1,2(CH3CO2)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 (Npy) 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 (NHsec), Npy 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.

The obtained results confirmed the different coordinating mode of the studied benzimidazole ligands towards Ni(II) and Zn(II) metal ion; [NiLCl2(OH2)3] and [ZnL(CH3CO2)2].Figure optionsDownload as PowerPoint slideHighlights
► [NiL1,2Cl2(OH2)3] and [ZnL1,2(CH3CO2)2] benzimidazole complexes were synthesized.
► Biological activity is affected by the nature of the substituent on aniline ring.
► Two types of coordinated acetate groups are assigned in zinc complexes.
► Strong coordination bonds between ligands and metal ions as revealed by E2 values.