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

[MLCl ₂]·zH ₂O (L = (1H-benzimidazol-2-ylmethyl) -N-phenyl amine; M = Pd, z = 0; M = Pt, z = 1) and [PdL(OH ₂) ₂]·2X·zH ₂O (X = Br, I, NO ₃, 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 (N _py) of the benzimidazole ring and secondary amino group (NH _sec). 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 (IC ₅₀ = 12.4 μM) against breast cancer compared with that reported for cis-platin 9.91 μM.