Nmr relaxation studies in solution of transition metal complexes. IV. Equilibrium dynamics in aqueous solution of copper(II)-glycylglycine system

I. Nagypál, Ferenc Debreczeni

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Abstract

The dynamics of equilibrium in aqueous solution of copper(II)-glycylglycine system has been studied by NMR relaxation method. The relaxation rate measured in solutions with 1:1 metal-ligand concentration ratios was found to be the linear combination of the concentration of the complexes formed. A very small molar relaxation coefficient was found for the binuclear Cu2(LH-1)2OH complex. This may be explained by spin-pairing through the bridging OH ligand. The high value for the Cu(LH-1)OH complex is interpreted by a fast proton exchange between the bulk water and the coordinated OH- ligand. p]The ligand exchange rate constant for the CuL(LH-1)- + L *-⇌Cu L *(LH-1)- + L- process was found to be 4.5 × 107 M- s-. It is assumed that the incoming ligand replaces the -COO- group of the ligand coordinated in LH-1 form, thus the ligand exchange takes place without Jahn-Teller inversion. It was found that the -NH2 - H2O proton exchange processes are also influencing the measured relaxation data. Their rate constants are also given. The paramagnetic relaxation time for the -NH2 protons of the ligand coordinated in L- form in the CuL(LH-1 complex was found to be 2.1 × 10-6 sec.

Original languageEnglish
Pages (from-to)207-211
Number of pages5
JournalInorganica Chimica Acta
Volume58
Issue numberC
DOIs
Publication statusPublished - 1982

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Glycylglycine
Coordination Complexes
Metal complexes
Transition metals
Copper
transition metals
Ligands
aqueous solutions
copper
ligands
Protons
protons
Rate constants
Ion exchange
L Forms
Relaxation time
LH 1
relaxation time
Metals
Nuclear magnetic resonance

ASJC Scopus subject areas

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

Cite this

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abstract = "The dynamics of equilibrium in aqueous solution of copper(II)-glycylglycine system has been studied by NMR relaxation method. The relaxation rate measured in solutions with 1:1 metal-ligand concentration ratios was found to be the linear combination of the concentration of the complexes formed. A very small molar relaxation coefficient was found for the binuclear Cu2(LH-1)2OH complex. This may be explained by spin-pairing through the bridging OH ligand. The high value for the Cu(LH-1)OH complex is interpreted by a fast proton exchange between the bulk water and the coordinated OH- ligand. p]The ligand exchange rate constant for the CuL(LH-1)- + L *-⇌Cu L *(LH-1)- + L- process was found to be 4.5 × 107 M- s-. It is assumed that the incoming ligand replaces the -COO- group of the ligand coordinated in LH-1 form, thus the ligand exchange takes place without Jahn-Teller inversion. It was found that the -NH2 - H2O proton exchange processes are also influencing the measured relaxation data. Their rate constants are also given. The paramagnetic relaxation time for the -NH2 protons of the ligand coordinated in L- form in the CuL(LH-1 complex was found to be 2.1 × 10-6 sec.",
author = "I. Nagyp{\'a}l and Ferenc Debreczeni",
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AU - Nagypál, I.

AU - Debreczeni, Ferenc

PY - 1982

Y1 - 1982

N2 - The dynamics of equilibrium in aqueous solution of copper(II)-glycylglycine system has been studied by NMR relaxation method. The relaxation rate measured in solutions with 1:1 metal-ligand concentration ratios was found to be the linear combination of the concentration of the complexes formed. A very small molar relaxation coefficient was found for the binuclear Cu2(LH-1)2OH complex. This may be explained by spin-pairing through the bridging OH ligand. The high value for the Cu(LH-1)OH complex is interpreted by a fast proton exchange between the bulk water and the coordinated OH- ligand. p]The ligand exchange rate constant for the CuL(LH-1)- + L *-⇌Cu L *(LH-1)- + L- process was found to be 4.5 × 107 M- s-. It is assumed that the incoming ligand replaces the -COO- group of the ligand coordinated in LH-1 form, thus the ligand exchange takes place without Jahn-Teller inversion. It was found that the -NH2 - H2O proton exchange processes are also influencing the measured relaxation data. Their rate constants are also given. The paramagnetic relaxation time for the -NH2 protons of the ligand coordinated in L- form in the CuL(LH-1 complex was found to be 2.1 × 10-6 sec.

AB - The dynamics of equilibrium in aqueous solution of copper(II)-glycylglycine system has been studied by NMR relaxation method. The relaxation rate measured in solutions with 1:1 metal-ligand concentration ratios was found to be the linear combination of the concentration of the complexes formed. A very small molar relaxation coefficient was found for the binuclear Cu2(LH-1)2OH complex. This may be explained by spin-pairing through the bridging OH ligand. The high value for the Cu(LH-1)OH complex is interpreted by a fast proton exchange between the bulk water and the coordinated OH- ligand. p]The ligand exchange rate constant for the CuL(LH-1)- + L *-⇌Cu L *(LH-1)- + L- process was found to be 4.5 × 107 M- s-. It is assumed that the incoming ligand replaces the -COO- group of the ligand coordinated in LH-1 form, thus the ligand exchange takes place without Jahn-Teller inversion. It was found that the -NH2 - H2O proton exchange processes are also influencing the measured relaxation data. Their rate constants are also given. The paramagnetic relaxation time for the -NH2 protons of the ligand coordinated in L- form in the CuL(LH-1 complex was found to be 2.1 × 10-6 sec.

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