Synthesis, characterization, biological activity, and modelling protein docking of divalent, trivalent, and tetravalent metal ion complexes of new azo dye ligand (N,N,O) derived from benzimidazole

Abstract

The ligand 2-[2′-(benzimidazole)azo]-4,6-dimethyl benzoic acid (BADMB) was employed to create coordination complexes with Pd(II), Co(III), and Pt(IV) ions. A variety of analytical methods were utilized to verify the structures of the synthesized chelates, including microanalysis, ¹H NMR, ¹³C NMR, UV–Vis spectroscopy, FT-IR, mass spectrometry, magnetic susceptibility, molar conductivity, X-ray diffraction (XRD), and thermal analysis. The stoichiometry of the metal complexes was 1:1 [M:L] in the case of both Pd(II) and Pt(IV) complexes while that of the Co(III) complex was 1:2 [M:L]. The results of molar conductivity measurements confirmed that all of the complexes are electrolytes and that they fall within the range 15.74–40.11 Ω⁻¹ cm² mol⁻¹. The findings indicated that the Co(III) and Pt(IV) complexes adopt an octahedral geometry, with the formulas [Co(BADMB)₂]Cl·H₂O and [Pt(BADMB)Cl₃]·H₂O, respectively. In contrast, the Pd(II) complex, represented by the general formula [Pd(BADMB)Cl]·H₂O, has a square planar geometry. BADMB acts as a trident (N,N,O) ligand through two nitrogen atoms from the benzimidazole ring and an azo group and one oxygen atom of the carboxyl group. The antimicrobial activity of these compounds was evaluated against a variety of microorganisms, including Streptococcus, Staphylococcus aureus, Penicillium spp., and Aspergillus, as well as multidrug resistance. In addition, all compounds were active against Penicillium spp. fungi compared to the other microorganisms examined. Moreover, the cytotoxic effects of the BADMB, Pd(II), and Pt(IV) complexes were evaluated in a human hepatocellular carcinoma cell line (HepG2) and a normal cell line (WRL68). A molecular docking study was performed using MOE 2015 software and the PDBsum online server. The compounds showed a binding free energy greater than 5 kcal/mol and an RMSD value was present in the range of 1.41 to 2.01 Å, indicating their potential as ligands for further molecular studies with selected targets.