NMR relaxation studies in solutions of transition metal complexes. VI. Equilibria and proton exchange processes in aqueous solutions of VO2+-glycine system

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Abstract

The equilibria in aqueous solution of the VO2+-glycine system has been studied by pH-metry in very high ligand excess, to avoid the hydrolysis of vanadyl ions. The complexes VOG+, VOG2, VOGH2+, VOG2- H+ and VOG2H- -1 = VOG2(OH)- are dominating in the system; their formation constants are given. The formation of complexes of VOGH-1 = VOG(OH), VOGH- -2 = VOG(OH)- 2 and (VO)2G2H-2 = (VO)2G2(OH)2 have also been detected. It is stated that the VO2G2(OH)2 is not the only binuclear (polynuclear) complex in the system; the composition of the other polynuclear complexes, however, cannot be stated unambiguously because of their very low concentrations. The rate constants of the proton exchange between the bulk water and the different complexes have been determined by measuring the T2 relaxation time of the water protons. In contrast to the oxalate, and some other vanadyl complexes, the rate constant decreases by the decrease of the number of water molecules remaining in the first coordination sphere of the vanadyl ion. The exceedingly high proton exchange rate constant for the VOG2(OH)- mixed hydroxo complex is interpreted as being due to the direct proton exchange between the bulk water and the coordinated OH group.

Original languageEnglish
Pages (from-to)193-199
Number of pages7
JournalInorganica Chimica Acta
Volume62
Issue numberC
DOIs
Publication statusPublished - 1982

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Coordination Complexes
glycine
Metal complexes
Glycine
Transition metals
Vanadates
Protons
Amino acids
Ion exchange
transition metals
Nuclear magnetic resonance
aqueous solutions
Rate constants
nuclear magnetic resonance
protons
Water
water
Ions
Oxalates
oxalates

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry
  • Physical and Theoretical Chemistry
  • Materials Chemistry

Cite this

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title = "NMR relaxation studies in solutions of transition metal complexes. VI. Equilibria and proton exchange processes in aqueous solutions of VO2+-glycine system",
abstract = "The equilibria in aqueous solution of the VO2+-glycine system has been studied by pH-metry in very high ligand excess, to avoid the hydrolysis of vanadyl ions. The complexes VOG+, VOG2, VOGH2+, VOG2- H+ and VOG2H- -1 = VOG2(OH)- are dominating in the system; their formation constants are given. The formation of complexes of VOGH-1 = VOG(OH), VOGH- -2 = VOG(OH)- 2 and (VO)2G2H-2 = (VO)2G2(OH)2 have also been detected. It is stated that the VO2G2(OH)2 is not the only binuclear (polynuclear) complex in the system; the composition of the other polynuclear complexes, however, cannot be stated unambiguously because of their very low concentrations. The rate constants of the proton exchange between the bulk water and the different complexes have been determined by measuring the T2 relaxation time of the water protons. In contrast to the oxalate, and some other vanadyl complexes, the rate constant decreases by the decrease of the number of water molecules remaining in the first coordination sphere of the vanadyl ion. The exceedingly high proton exchange rate constant for the VOG2(OH)- mixed hydroxo complex is interpreted as being due to the direct proton exchange between the bulk water and the coordinated OH group.",
author = "I. F{\'a}bi{\'a}n and I. Nagyp{\'a}l",
year = "1982",
doi = "10.1016/S0020-1693(00)88501-1",
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T1 - NMR relaxation studies in solutions of transition metal complexes. VI. Equilibria and proton exchange processes in aqueous solutions of VO2+-glycine system

AU - Fábián, I.

AU - Nagypál, I.

PY - 1982

Y1 - 1982

N2 - The equilibria in aqueous solution of the VO2+-glycine system has been studied by pH-metry in very high ligand excess, to avoid the hydrolysis of vanadyl ions. The complexes VOG+, VOG2, VOGH2+, VOG2- H+ and VOG2H- -1 = VOG2(OH)- are dominating in the system; their formation constants are given. The formation of complexes of VOGH-1 = VOG(OH), VOGH- -2 = VOG(OH)- 2 and (VO)2G2H-2 = (VO)2G2(OH)2 have also been detected. It is stated that the VO2G2(OH)2 is not the only binuclear (polynuclear) complex in the system; the composition of the other polynuclear complexes, however, cannot be stated unambiguously because of their very low concentrations. The rate constants of the proton exchange between the bulk water and the different complexes have been determined by measuring the T2 relaxation time of the water protons. In contrast to the oxalate, and some other vanadyl complexes, the rate constant decreases by the decrease of the number of water molecules remaining in the first coordination sphere of the vanadyl ion. The exceedingly high proton exchange rate constant for the VOG2(OH)- mixed hydroxo complex is interpreted as being due to the direct proton exchange between the bulk water and the coordinated OH group.

AB - The equilibria in aqueous solution of the VO2+-glycine system has been studied by pH-metry in very high ligand excess, to avoid the hydrolysis of vanadyl ions. The complexes VOG+, VOG2, VOGH2+, VOG2- H+ and VOG2H- -1 = VOG2(OH)- are dominating in the system; their formation constants are given. The formation of complexes of VOGH-1 = VOG(OH), VOGH- -2 = VOG(OH)- 2 and (VO)2G2H-2 = (VO)2G2(OH)2 have also been detected. It is stated that the VO2G2(OH)2 is not the only binuclear (polynuclear) complex in the system; the composition of the other polynuclear complexes, however, cannot be stated unambiguously because of their very low concentrations. The rate constants of the proton exchange between the bulk water and the different complexes have been determined by measuring the T2 relaxation time of the water protons. In contrast to the oxalate, and some other vanadyl complexes, the rate constant decreases by the decrease of the number of water molecules remaining in the first coordination sphere of the vanadyl ion. The exceedingly high proton exchange rate constant for the VOG2(OH)- mixed hydroxo complex is interpreted as being due to the direct proton exchange between the bulk water and the coordinated OH group.

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