Iron(III), copper(II), cadmium(II), and mercury(II) complexes of isatin carbohydrazone Schiff base ligand (H<sub>3</sub>L): Synthesis, characterization, X‐ray diffraction, cyclic voltammetry, fluorescence, density functional theory, biological activity, and molecular docking studies
Adel M. Younis, Mohammed M. El‐Gamil, Tawfik H. Rakha, Gaber M. Abu El‐Reash
Abstract
A series of some transition metal, Fe(III), Cu(II), Cd(II), and Hg(II), complexes with N ′,2‐bis(( Z )‐2‐oxoindolin‐3‐ylidene)hydrazine‐1 carbohydrazide (H 3 L) ligand have been synthesized, and their structures were elucidated based on their spectral analyses (Fourier transform infrared [FT‐IR], 1 H nuclear magnetic resonance (NMR) and 13 C NMR, UV‐visible (UV‐Vis), electron spin resonance (ESR), powder X‐ray diffraction [XRD], and mass spectroscopy), elemental analyses, conductance, and magnetic susceptibility measurements. The structures of the H 3 L ligand and its metal complexes were optimized using the DMol 3 tool in the material studio package. The ligand behaves as binegative N 2 O 3 pentadentate in [Fe(HL)(Cl)]·2H 2 O complex, mononegative N 2 O 3 pentadentate in [Cu(H 2 L)(OAc)]·2H 2 O complex, mononegative N 2 O tridentate in [Cd(H 2 L) 2 ]·H 2 O complex, and finally, neutral N 2 bidentate in [Hg(H 3 L)(Cl) 2 ]·2H 2 O complex. Coats–Redfern and Horowitz–Metzger methods were used to estimate the various thermodynamic and kinetic parameters. Cyclic voltammetry of the ligand in the absence and presence of Cd(II) and Hg(II) ions was studied. Fluorescence studies were performed in DMSO and showed that Cu(II) ions quench the fluorescence spectrum of the free ligand, whereas Cd(II) ions enhance it. The in vitro antimicrobial activities of the free ligand and its complexes against different bacterial strains and fungi Candida albicans were screened using agar‐disc diffusion techniques. The antioxidant potentials of the isolated compounds were also screened by employing SOD and ABTS free radical scavenging methods. Molecular docking studies were performed using Auto‐Dock tools to predict the best binding mode and predominant binding interactions.