Structural and in vitro cytotoxicity studies on 1H-benzimidazol-2-ylmethyl-N-phenyl amine and its Pd(II) and Pt(II) complexes

[MLCl2]·zH2O (L = (1H-benzimidazol-2-ylmethyl)-N-phenyl amine; M = Pd, z = 0; M = Pt, z = 1) and [PdL(OH2)2]·2X·zH2O (X = Br, I, NO3, z = 0; X = SCN, z = 1) complexes were synthesized as potential anticancer compounds and characterized by elemental analysis, spectral and thermal methods. FT-IR and 1H NMR studies revealed that the benzimidazole L is coordinated to the metal ions via the pyridine-type nitrogen (Npy) of the benzimidazole ring and secondary amino group (NHsec). Quantum mechanical calculations of energies, geometries, vibrational wavenumbers, and 1H NMR of the benzimidazole L and its complexes were carried out by density functional theory using B3LYP functional combined with 6-31G(d) and LANL2DZ basis sets. Natural bond orbitals (NBOs) and frontier molecular orbitals were performed at B3LYP/LANL2DZ level of theory. The synthesized ligand, in comparison to its metal complexes was screened for its antibacterial activity. The benzimidazole L is more toxic against the bacterium Staphylococcus aureus (MIC = 58 μg/mL) than the standard tetracycline (MIC = 82 μg/mL). The complexes showed cytotoxicity against breast cancer, Colon Carcinoma, and human heptacellular Carcinoma cells. The platinum complex (6) displays cytotoxicity (IC50 = 12.4 μM) against breast cancer compared with that reported for cis-platin 9.91 μM.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights• Assignments of all the fundamental vibrational modes of the benzimidazole L and its complexes were examined and proposed at high level of theory. • The inclusion of solvation to the 1H NMR calculations is necessary especially for acidic protons in order to obtain accurate values. • Square planar geometry is assigned to the studied complexes through N, N ligand and 2Cl. • The studied ligand (58 μg/mL) is more toxic against the bacterium Staphylococcus aureus than tetracycline (82 μg/mL) and its complexes. • The platinum complex displays cytotoxicity (12.4 μM) against breast cancer compared with that reported for cis-platin 9.91 μM.