Pt(IV) and Au(III) complexes with tridentate-benzothiazole based ligand: synthesis, characterization, biological applications (antibacterial, antifungal, antioxidant, anticancer and molecular docking) and DFT calculation

Abstract

A novel tridentate azo dye ligand, 2-[2′-(6-methoxybenzothiazolyl)azo]-5-dimethylamino benzoic acid (6-MBTADB) and its Pt(IV) and Au(III) metal complexes have been synthesized. The proposed structures were defined from elemental analysis, molar conductivity, magnetic susceptibility, atomic absorption spectrophotometry,1H NMR, 13C NMR, FT-IR, UV–Vis, mass spectra, X-ray diffraction analysis (XRD), thermal analysis (TGA/DTA) and field emission scanning electron microscopy (FE-SEM). Based on analytical and spectroscopic data, suitable geometry has been suggested for all complexes. The 6-MBTADB ligand acts as a tridentate via NNO donors towards the metal ions inside octahedral geometry with Pt(IV), and square planner with Au(III) ion. Quantum chemical calculations were performed on the compounds using density functional theory DFT/B3LYP, 6–311G (d,p), and LanL2DZ basis sets. Moreover, the synthesized compounds showed greater antimicrobial activity when tested biologically against Escherichia coli, Staphylococcus aureus, and Aspergillus niger. The results of their tests show that the metal complexes are more effective against several bacterial and fungal strains. Further, the free radical scavenging activity of the free ligand and metal complexes has been determined by their interaction with the stable DPPH free radical. The combined molecular docking study evaluates the binding energies of anticancer agents, providing the binding property with the receptor. The results of the molecular docking show that the ligand and its complexes have a good affinity with the protein kinase (1HK7). Finally, all the compounds exhibited significant antiproliferative activity against the human breast cancer (MCF-7) and normal HUVECs cell lines, showing that Pt(IV) chelate the most potent against MCF-7 cell line based on IC50 and selective indices (SI) values. This research may provide knowledge that is an excellent backdrop for the rational design of promising drugs.