Reaction of thiosemicarbazide with some divalent ions: Synthesis, characterization, molecular modeling, and evaluation of the catalytic and biological activity of the complexes

ABSTRACT

New metal complexes of Co(II) and Cu(I) have been synthetized by reaction of metal salts with thiosemicarbazide (TSC: HL¹) and urea (U). The metal complexes were characterized on the basis of elemental analyses, molar conductance, spectral (IR, ¹H NMR) studies, as well as thermogravimetric analysis. The spectral data show that in the complexes, only TSC is coordinated to the metal. The IR spectra of Co(II) and Cu(I) complexes are different. In addition to the bands of TSC, a new intense band at 2100 cm⁻¹ is assigned to the thiocyanate fragment produced in situ by the cleavage of the TSC C–N bond. On the basis of spectral studies, a N₃O₃ high-spin environment was assigned to [Co^(II)(L¹)(SCN)(H₂O)₃] complex and a dimeric form geometry for Cu(I) complex of general formula [Cu^(I)(HL¹)(SCN)(H₂O)]. In order to gain a better insight into the molecular structure and the reactivity of the ligand and its complexes, quantum chemical calculations were also performed to determine some electronic properties and geometric parameters of the ligand and Cu(I) and Co(II) complexes. The metal complexes have been tested for catalase-like activity in order to assess their catalytic properties. The results seem encouraging. The biological activity of the ligand and its metal complexes is evaluated as well.

KEYWORDS:

• Thiosemicarbazide
• metal complexes
• spectral studies
• molecular optimization
• catalase-like and biological activities

Acknowledgment

The authors wish to thank David Rinaldo (Schrodinger LLC) for technical assistance and Ahmed Chergui for the mechanism of C-N cleavage.