Synthesis, spectroscopic characterization and biological studies of nano-sized Co(II), Ni(II), Cu(II) and Zn(II) Schiff's base hybrids

Abstract

A novel series of nano-sized Co(II), Ni(II), Cu(II) and Zn(II) hybrids has been synthesized using the template method, i.e. by the in situ reaction of oxazin–Schiff's base [(E)-3-(2-(4-(diethylamino)-2-mercaptobenzylidene)hydrazineyl)-2H-benzo[b][1,4]oxazin-2-one] (HL) derived from 4-(diethylamino)-2-mercaptobenzaldehyde with 3-hydrazineyl-2H-benzo[b][1,4]oxazin-2-one in the presence of Co(II), Ni(II), Cu(II), Zn(II) chloride in ethanol. The structures and geometry of the optained compounds have been described by using the different analytical and spectroscopic tools such as elemental analysis, UV-VIS, IR, MS, 1H NMR, ESR, CV, TGA, XRD, SEM, AFM, magnetic and molar conductivity measurements. IR spectral studies confirmed the coordination of the ligand to the metal ions through the thiol sulfur, azomethine nitrogen and carbonyl oxygen. The Schiff's base ligand acts as monobasic tridentate OSN donor. The geometrical structures have been found to be octahedral and tetrahedral. The molar conductance measurements of the nano-sized hybrids in DMF and DMSO correspond to be nonelectrolytic nature for all nano-sized metal (II) hybrids. The elemental analyses confirm 1 M: 2 L stoichiometry of the type [ML2] (M = Co(II), Ni(II), Cu(II) and Zn(II)). Electrochemical behaviour of nano-sized metal (II) hybrids were determined by cyclic voltammetry. Degradation pattern of the ligand HL and its nano-sized hybrids is shown by thermal studies. The activation of thermodynamic parameters are calculated using Coast-Redfern (CR) and Horowitz-Metzger (HM) methods. The data obtained from XRD, SEM, TEM and AFM images unequivocally asserted the nano-sized metal chelates. The percentage antioxidant activities are also more for complexes than the ligand. The investigated ligand and metal complexes were screened for their in-vitro antimicrobial activities against different types of fungal and bacterial strains. The resulting data assert on the inspected compounds as a highly promising bactericides and fungicides. The antitumor activities of all synthesized compounds were evaluated towards human liver Carcinoma (HepG2) cell line. DNA-binding, DNA cleavage and fluorescence properties of nano-sized hybrids with this ligand are reported.