Investigation of spectroscopic, thermal, and biological properties of FeII, CoII, ZnII, and RuII complexes derived from azo dye ligand

In this study, the novel azo dye FeII, CoII, ZnII, and RuII complexes with an azo dye ligand (L: (E)-4-((4-methoxyphenyl)diazenyl)-3-methyl-1H-pyrazol-5-amine) were synthesized. The structures of the complexes were characterized by FT-IR, elemental analysis, UV-Vis, mass spectra (FeII and CoII), NMR spectra (only diamagnetic ZnII and RuII), thermogravimetric and differential thermal analysis (TGA-DTA). All of the newly synthesized compounds were tested for their biochemical properties, including enzyme inhibitory and antioxidant activities. According to the in vitro ABTS, DPPH, CUPRAC, and FRAP antioxidant methods, the ligand and its metal complexes showed close antioxidant activities to the standards (BHA, BHT, ascorbic acid, and α-tocopherol). Enzyme inhibitions of the metal complexes were investigated against glutathione S-transferase (GST), acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) enzymes. The best inhibition values (Ki) were observed for Ru(II) complex against GST (14.36 ± 2.16 µM), AChE (16.86 ± 2.74 µM), and BChE (14.12 ± 2.04 µM).