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

This study explores the synthesis of coordination complexes using the ligand (BADMB) with Pd(II), Co(III), and Pt(IV) ions. Characterization through various analytical techniques confirmed their structures and geometries: octahedral for Co(III) and Pt(IV), and square planar for Pd(II). Antimicrobial activity was significant against Streptococcus and Penicillium spp. Cytotoxic effects were evaluated on HepG2 and WRL68 cell lines. Molecular docking studies indicated strong binding interactions with a hepatocellular carcinoma receptor, suggesting potential for further research in cancer treatment and antimicrobial applications. • BADMB was used to form coordination complexes with Pd(II) , Co(III) , and Pt(IV) ions. • Co(III) and Pt(IV) complexes adopt an octahedral geometry, while the Pd(II) complex has a square planar geometry. • The metal complexes exhibited significant antimicrobial activity, particularly against Streptococcus , Staphylococcus aureus , Penicillium spp. , and Aspergillus . • Cytotoxic effects were assessed on HepG2 cancer cells and a normal cell line ( WRL68 ). • Docking studies indicated strong interactions with the protein receptor (PDB ID: 3S35). 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, 1 H NMR, 13 C 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 cm 2 mol −1 . The findings indicated that the Co(III) and Pt(IV) complexes adopt an octahedral geometry, with the formulas [Co(BADMB) 2 ]Cl·H 2 O and [Pt(BADMB)Cl 3 ]·H 2 O, respectively. In contrast, the Pd(II) complex, represented by the general formula [Pd(BADMB)Cl]·H 2 O, 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.

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