Synthesis and spectroscopic characterization of N-substituted thiosemicarbazone complexes

Complexation between Co(II), Ni(II), and Cu(II) with some 3,4-hexanedione bisN-substituted thiosemicarbazones] has been investigated. The ligands release the two hydrazine hydrogens during the complex formation and act as binegative tetradentate (N₂S₂) except Cu(H₂Hx4M)Cl₂] and Cu(H₂Hx4Et)Cl₂]2H₂O in which the ligands behave as neutral tetradentate. The magnetic moments and electronic spectra provide information about the geometry of the complexes, which is supported by calculating the ligand field parameters for the Co(II) complexes. Most Ni(II) complexes are diamagnetic, indicative of a square-planar structure. The bands observed in Nujol are shifted to higher energies in dimethylformamide (DMF) solution, suggesting a weak interaction with the solvent. The ESR spectra of the complexes in solid and DMF solution exhibit axial symmetric g-tensor parameters with g _|>g _⊥>2.0023. The molecular parameters of Ni(Hx4M)] have been calculated theoretically by semiempirical PM3 method. Also, the electronic transitions were calculated theoretically and found approximately similar to those recorded experimentally.