Complexes of pyridoxal thiosemicarbazones formed with vanadium(IV/V) and copper(II): Solution equilibrium and structure

Tamás Jakusch, Károly Kozma, Éva A. Enyedy, Nóra V. May, Alexander Roller, Christian R. Kowol, Bernhard K. Keppler, Tamás Kiss

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The stoichiometry and thermodynamic stability of vanadium(IV/V) and copper(II) complexes of pyridoxal thiosemicarbazone and pyridoxal-N3,N3-dimethylthiosemicarbazone have been determined by pH-potentiometry (VIVO), EPR (VIVO/CuII), UV–Vis (CuII, VIVO and VV) and 51V NMR spectroscopy (VV) in 30% (w/w) dimethyl sulfoxide/water solvent mixture. In all cases, mono-ligand complexes are formed in different protonation states. In addition, the proton-dissociation constants of the ligands were also determined by pH-potentiometry, UV–Vis and 1H NMR spectroscopy. The solid state structures of the monoprotonated forms (VVO2(L1H)×1.5H2O and VVO2(L2H)×0.8H2O) of the VV complexes were characterized by single-crystal X-ray diffraction analysis. The mono-ligand complexes of CuII and VV are dominant at physiological pH. With all investigated metal ions the pyridoxal moiety of the ligand causes an extra deprotonation step between pH 4 and 7 due to the non-coordinating pyridine-NH+. The pyridoxal-containing ligands form somewhat more stable complexes with both VIVO and CuII ions than the reference compound salicylaldehyde thiosemicarbazone. Dimethylation of the terminal amino group resulted in the formation of VV and CuII complexes with even higher stability.

Original languageEnglish
Pages (from-to)243-253
Number of pages11
JournalInorganica Chimica Acta
Publication statusPublished - Mar 1 2018


  • Copper
  • Pyridoxal
  • Stability constants
  • Thiosemicarbazone
  • Vanadium
  • X-ray crystal structure

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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