Oxovanadium(IV) complexes based on S-alkyl-thiosemicarbazidato ligands. Synthesis, characterization, electrochemical, and antioxidant studies


Ilhan-Ceylan B., Tuzun E., Kurt Y., Acikgoz M., KAHRAMAN S., Atun G., ...More

JOURNAL OF SULFUR CHEMISTRY, vol.36, no.4, pp.434-449, 2015 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 36 Issue: 4
  • Publication Date: 2015
  • Doi Number: 10.1080/17415993.2015.1050396
  • Journal Name: JOURNAL OF SULFUR CHEMISTRY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.434-449
  • Istanbul University Affiliated: Yes

Abstract

Reaction of VOSO4 with 2-hydroxy-napthaldeyde-S-R-thiosemicarbazones (R: methyl, ethyl, propyl or allyl) and salicyl aldehyde yielded five-coordinate oxovanadium(IV) complexes having a N-1,N-4-diarylidene-S-R-thiosemicarbazidato structures. The compounds were characterized by elemental analysis, magnetic measurements, electronic, infrared, H-1-NMR, and electron paramagnetic resonance (EPR) spectra. The X-band EPR signals were recorded from powder forms and also in solution. All the complexes have a single asymmetric line shape and theoretical fit studies prove the presence of axial symmetry around the paramagnetic vanadium ions. A computer simulation of the EPR spectrum of each complex was carried out to derive the related EPR parameters. Cyclic voltammograms of the complexes exhibited two metal-based reversible redox peaks around 500 and -800 mV corresponding to one electron oxidation/reduction of (VO)-O-IV/(VO)-O-V and (VO)-O-IV/(VO)-O-III, respectively. The reductive response in the 50-350 mV region was assigned to ligand reduction. Antioxidant activities of the compounds were determined with CUPric Reducing Antioxidant Capacity, 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid, and 1,1-diphenyl-2-picrylhydrazyl assays. The test results indicated that the antioxidant capacity of the compounds increases with the carbon number of saturated hydrocarbon chain on sulfur atom.