Novel palladium(II) and platinum(II) complexes with 1H-benzimidazol-2-ylmethyl-N-(4-bromo-phenyl)-amine: Structural studies and anticancer activity

[MLCl2] (L = (1H-benzimidazol-2-ylmethyl)-N-(4-bromo-phenyl)-amine; M = Pd & Pt) and [PdL(OH2)2]∙2X∙zH2O (X = Br, I, z = 2; X = SCN, z = 1; X = NO3, z = 0) complexes have been synthesized as potential anticancer compounds and their structures were elucidated using elemental analysis, spectral, thermal analysis and X-ray powder diffraction. The benzimidazole (L) crystallizes in the space group P21/c with a = 8.6660(3) Å, b = 16.6739(7) Å, c = 9.8611(4) Å and β = 113.505(3) ° and forms an infinite chain structure with a trans-zigzag type along the crystallographic axis "a", through the intermolecular H–bond. FT-IR and 1H NMR studies revealed that the ligand L is coordinated to the metal ion 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 DFT/B3LYP method combined with 6–31G(d) and LANL2DZ basis sets. Natural bond orbital (NBO) analysis and frontier molecular orbitals (FMO) were performed at B3LYP/LANL2DZ level of theory. The benzimidazole L, in comparison to its metal complexes was screened for its antibacterial activity. The complexes showed cyctotoxic effects against human breast cancer (MCF7), hepatocarcinoma (HepG2) and colon carcinoma cells (HCT). The platinum complex (6) exhibited a moderate antitumor activity against MCF7 with IC50 = 10.2 μM comparing to that reported for cis-platin 9.91 μM.

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► The platinum complex exhibits a moderate antitumor activity against MCF7.
► The higher toxicity of Pd-L than Pt-L is due to slow ligand-exchange behavior.
► Ligand is more toxic against the studied bacteria than its complexes.
► Excellent agreement is found between the theoretical and experimental data.