Spectral and thermal studies for some transition metal complexes of bis(benzylthiocarbohydrazone) focusing on EPR study for Cu(II) and VO2+

The coordination behavior of bis (benzylthiocarbohydrazone) as a macrocyclic ligand (H2BBTC), towards Co(II), Ni(II), Cu(II) nitrates, Cd(II) and Pt(IV) chlorides as well as VO2+ sulphate has been investigated. The elemental analysis, magnetic moments, spectral (UV–vis, IR, 1H NMR and EPR) with thermal studies were used to characterize the isolated complexes. The IR spectra showed that the ligand acts as a binegative hexadentate donor through NH groups and thiol S atoms. Electronic and magnetic data proposed the octahedral structure for all complexes under investigation, except VO2+, is a square-pyramidal geometry. EPR spectra for VO2+ and Cu(II) reveal data confirmed the proposed structures. The ionization constants (pK1 = 8.3 and pK2 = 7.7) of the ligand and the stability constants of its complexes in solution were determined. The TG analysis for most complexes supports the absence of solvent molecules in or out the coordination sphere through the high thermal stability observed on the thermal curves for the investigated complexes.