Chelating activity of bis(diacetylmonoxime)thiocarbohydrazone towards VO2+, Co(II), Ni(II), Cu(II) and Pt(IV) ions

A new chelating agent, bis(diacetylmonoxime)thiocarbohydrazone (H₃DMT), has been synthesized from reaction between diacetylmonoxime and thiocarbohydrazide. The prepared ligand, characterized by elemental analysis, IR and ¹H?NMR spectra, is a strong chelating agent and indicator. Its coordinating properties have been studied toward VO²⁺, Co(II), Ni(II), Cu(II) and Pt(IV) ions. The data revealed the formation of mononuclear complexes with Co(II) and Pt(IV) and binuclear complexes with the rest. In all complexes, the ligand binds in its deprotonated form through the oxime and hydrazone nitrogens as well as the thiol or thione sulfur forming five- and six-membered rings. All complexes exhibit an octahedral structure except for the Cu(II) which has a square-pyramidal geometry based on the spectral and magnetic studies. The ESR spectra of the Cu(II) and VO²⁺ complexes are in good agreement with the structural results. The color change from acidic (yellow) to basic (reddish brown) media gives the ligand the ability to become as an analytical indicator for weak acid–weak base titrations.