Synthesis, spectral characterization, antimicrobial evaluation studies and cytotoxic activity of some transition metal complexes with tridentate (N,N,O) donor azo dye ligand

Abstract

A new azo dye ligand 2-[2'-(6-methoxybenzothiazolyl)azo]-4-ethoxyphenol (6-MBTAEP) was prepared by reacting a diazonium chloride salt solution of 2-amino-6-methoxy benzothiazole and coupled with 4-ethoxy phenol in an alkaline ethanolic solution. The synthesized ligand (6-MBTAEP) was applied for complexation with various metal ions, such as Ag(I), Pt(IV) and Au(III). Differing spectral techniques have been used to study the structures of the azo dye ligand (6-MBTAEP) and chelate complexes such as elemental analysis (C.H.N.S), Mass spectrum, 1H NMR, 13C NMR, FT-IR, UV–Vis, XRD, thermal analysis (TGA-DTA), FE-SEM, and magnetic measurements. Molar conductivity indicates the complexes are non-electrolytes and do not have conductive species except for Au(III)-Complex. The results confirmed that the ligand (N, N, O) behaves as a tridentate and coordinates to the metal ion via the nitrogen atom of the azomethine group (C=N) of heterocyclic benzothiazole molecule, nitrogen atom of the azo group (N=N) which is the farthest of benzothiazole ring and the oxygen atom of the phenolic ring. The biological activity of the free ligand (6-MBTAEP) and prepared metal complexes were tested against Staphylococcus aureus (Gram-positive), Escherichia coli (Gram-negative) as antibacterial, and Aspergillus Niger as an antifungal. The data show that the complexes are more effective against bacteria and less effective against fungi in comparison with standard antibacterials (Novobiocin) and antifungal drugs (Cycloheximide). Antioxidant studies of synthesized compounds were also performed by measuring the DPPH radical scavenging assay. The DPPH radical scavenging assay was used to measure the antioxidant activity of produced compounds and compared with the known antioxidant ascorbic acid. However, in vitro anticancer and toxicity of ligand (6-MBTAEP) and Pt(IV)-Complex were assessed by MTT cytotoxicity assay against lung cancer cell line (A549) and normal human umbilical vein endothelial cells (HUVEC). Furthermore, molecular docking studies have been conducted on the potent compounds that have several crucial interactions with EGFR proteins.