Characterization, cyclic voltammetry and biological studies of divalent Co, Ni and Cu complexes of water-soluble, bioactive and photoactive thiosemicarbazone salt

Abstract

Sodium(E)‑4‑hydroxy‑3‑((2‑(pyridin‑2‑ylcarbamothioyl)hydrazineylidene)methyl) benzenesulfonate (NaH3PyTSC) and its cobalt(II), nickel(II) and copper(II) chelates have been isolated. Different spectroscopic techniques have been utilized for elucidation of their structures. The 1HNMR spectrum of NaH3PyTSC illustrated the existence of three different isomers in DMSO solution; syn and anti-conformers of the thione form and the thiol form. The FTIR illustrated that NaH3PyTSC preforms as a bi-negative NOS tridentate in [CoH2PyTSC(H2O)]2.2H2O and [CuH2PyTSC(H2O)]2.H2O through the deprotonated thiol, (CN)azomethine and SO32− groups and also as binegative NNSO tetradentate in [NiH2PyTSC(H2O)]2.4H2O through deprotonated thiol, SO32−, (CN)azomethine and (CN)pyridyl groups. The spectral and magnetic studies proposes a tetrahedrally-coordinated Co(II) and Cu(II) complexes and interior bispin state originating from two distinct Oh and Td geometries for [NiH2PyTSC(H2O)]2.4H2O complex. The ESR data and its discussion coincide with the suggestion of distorted Td geometry for [CuH2PyTSC(H2O)]2.H2O complex. The ligand displayed maximum luminescent intensity at about 19,960 cm−1 whereas all complexes show an emission band at about 28,409 cm−1 and therefore they are photoactive compound. The cyclic voltammogram of copper complex indicates a reversible system including the transfer of one electron on every step in case of Cu(II) while that of Co(II) complex shows the transfer of two electrons in only one step. Kinetic and thermodynamic parameters of the isolated complexes for all decomposition steps are discussed. DFT optimization has been used to estimate different descriptors e.g. HOMO, LUMO, MEP and theoretical IR. DNA bioassay, antibacterial, antifungal, antioxidant and anticancer behaviors of the isolated frameworks have been studied.