Synthesis, characterization, DFT and biological studies of isatinpicolinohydrazone and its Zn(II), Cd(II) and Hg(II) complexes

• Preparation and characterization of Zn2+, Cd2+ and Hg2+ complexes of picolinic acid hydrazone.
• DFT studies, chemical reactivity, MEP, energy components and theoretical infrared intensities.
• Thermal behavior of the solid metal complexes was studied using TGA technique.
• The compounds were screened for antibacterial, DDPH antioxidant and antitumor activity.

Isatinpicolinohydrazone (H2IPH) and its Zn(II), Cd(II) and Hg(II) complexes have been synthesized and investigated using physicochemical techniques viz. IR, 1H NMR, 13C NMR, UV–Vis spectrometric methods and magnetic moment measurements. The investigation revealed that H2IPH acts as binegative tetradentate in Zn(II), neutral tridentate in Cd(II) and as neutral bidentate towards Hg(II) complex. Octahedral geometry is proposed for all complexes. The bond length, bond angle, chemical reactivity, energy components (kcal/mol), binding energy (kcal/mol) and dipole moment (Debyes) for all the title compounds were evaluated by DFT and also MEP for the ligand is shown. Theoretical infrared intensities of H2IPH and also the theoretical electronic spectra of the ligand and its complexes were calculated. The thermal behavior and the kinetic parameters of degradation were determined using Coats–Redfern and Horowitz–Metzger methods. The in vitro antibacterial studies of the complexes proved them as growth inhibiting agents. The DDPH antioxidant of the compounds have been screened. Antitumor activity, carried out in vitro on human mammary gland (breast) MCF7, have shown that Hg(II) complex exhibited potent activity followed by Zn(II), Cd(II) complexes and the ligand.

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