Structural Characterization, XRD, DFT Calculations, Docking, Antimicrobial, Anticancer Applications, and Electrochemical Performance Studies of Some New Schiff Base Transition Metal Complexes

Abstract

The condensation of 3-amino-1H-1,2,4-triazole with 2-benzoyl benzoic acid produced a novel Schiff base ligand (H₂L). The structure of synthesized H₂L and its metal complexes [Co(II), Ni(II), Cu(II), and Zr(IV)] were characterized by mass spectrometry, FT-IR, ¹H NMR, XRD, UV-vis, ESR, and TG-DTG analyses also, supported by computational approaches. FT-IR spectral data showed that H₂L acts in a tridentate mode through azomethine nitrogen, the nitrogen of triazole, and carboxylate group oxygen. XRD results indicated that compounds were polycrystalline with monoclinic systems for H₂L, Co(II), and Cu(II) compounds but orthorhombic systems for Zr(IV) and Ni(II) complexes. Coats–Redfern and Horowitz–Metzger equations were utilized. The optical characteristics of compounds were evaluated. From DFT, ΔE values of our complexes varied from 0.033 eV for the more reactive Co(II) complex to 0.109 eV for the less reactive Zr(IV)complex compared to H₂L (0.113 eV). Also, from σ values, complexes were considered soft compared to H₂L. The optical band gap (E_g) values were compared to those produced by DFT and found to be equivalent. H₂L and its metallic complexes were assessed for their antibacterial activity as well as their antifungal activity. The results indicated that the complexes exhibited significant antimicrobial efficacy. H₂L and its metal complexes were evaluated for cytotoxic activity against the ATB-37 colon cancer cell line. Notably, the Ni(II) and Cu(II) complexes exhibited significant cytotoxic effects than other compounds. H₂L and its complexes were subjected to molecular docking into TRK (PDB: 1t46), DHFR (PDB: 2W9H), PaaABC (PDB: 4IIT), and NatB (PDB: 5K04) to predict the activity or help in interpretation their cytotoxicity and antimicrobial potential. The electrochemical behavior of the metal complex–modified electrodes was assessed through cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) measurements, all performed in a 6-M KOH electrolyte. The results showed that Ni(II) complex–modified electrodes have much higher capacitance than other modified electrodes.