Aminocarboxylate complexes of vanadium(III): Electronic structure investigation by high-frequency and -field electron paramagnetic resonance spectroscopy

Joshua Telser, Chi Chin Wu, Kun Yuan Chen, Hua Fen Hsu, Dmitry Smirnov, Andrew Ozarowski, J. Krzystek

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Abstract

Aminocarboxylate complexes of vanadium(III) are of interest as models for biologically and medicinally relevant forms of this interesting and somewhat neglected ion. The V(III) ion is paramagnetic, but not readily suited to conventional EPR, due to its integer-spin ground state (S = 1) and associated large zero-field splitting (zfs). High-frequency and -field EPR (HFEPR), however, has the ability to study such systems effectively. Three complexes, all previously structurally characterized: Na[V(trdta)] · 3H2O, Na[V(edta)(H2O)] · 3H2O, and [V(nta)(H2O)3] · 4H2O (where trdta stands for trimethylenediamine-N,N,N′,N′-tetraacetate and nta stands for nitrilotriacetate) were studied by HFEPR. All the investigated complexes produced HFEPR responses both in the solid state, and in aqueous solution, but those of [V(nta)(H2O)3] · 4H2O were poorly interpretable. Analysis of multi-frequency HFEPR spectra yielded a set of spin Hamiltonian parameters (including axial and rhombic zfs parameters: D and E, respectively) for these first two complexes as solids: Na[V(trdta)] · 3H2O: D = 5.60 cm-1, E = 0.85 cm-1, g = 1.95; Na[V(edta)(H2O)] · 3H2O: D = 1.4 cm-1, E = 0.14 cm-1, g = 1.97. Spectra in frozen solution yielded similar parameters and showed multiple species in the case of the trdta complex, which are the consequence of the flexibility of this ligand. The EPR spectra obtained in frozen aqueous solution are the first, to our knowledge, of V(III) in solution in general and show the applicability of HFEPR to these systems. In combination with very insightful previous studies of the electronic absorption of these complexes which provided ligand-field parameters, it has been possible to describe the electronic structure of V(III) in [V(trdta)]- and [V(edta)(H2O)]-; the quality of data for [V(nta)(H2O)3] does not permit analysis. Qualitatively, six-coordinate V(III) complexes with O,N donor atoms show no electronic absorption band in the NIR region, and exhibit relatively large magnitude zfs (D ≥ 5 cm-1), while analogous seven-coordinate complexes do have a NIR absorption band and show relatively small magnitude zfs (D < 2 cm-1).

Original languageEnglish
Pages (from-to)487-495
Number of pages9
JournalJournal of Inorganic Biochemistry
Volume103
Issue number4
DOIs
Publication statusPublished - 2009 Apr 1

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Vanadium
Electron Spin Resonance Spectroscopy
Electronic structure
Paramagnetic resonance
Spectrum Analysis
Spectroscopy
Ions
Ligands
Absorption spectra
Hamiltonians
Ground state
Atoms

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Inorganic Chemistry

Cite this

Telser, Joshua ; Wu, Chi Chin ; Chen, Kun Yuan ; Hsu, Hua Fen ; Smirnov, Dmitry ; Ozarowski, Andrew ; Krzystek, J. / Aminocarboxylate complexes of vanadium(III) : Electronic structure investigation by high-frequency and -field electron paramagnetic resonance spectroscopy. In: Journal of Inorganic Biochemistry. 2009 ; Vol. 103, No. 4. pp. 487-495.
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abstract = "Aminocarboxylate complexes of vanadium(III) are of interest as models for biologically and medicinally relevant forms of this interesting and somewhat neglected ion. The V(III) ion is paramagnetic, but not readily suited to conventional EPR, due to its integer-spin ground state (S = 1) and associated large zero-field splitting (zfs). High-frequency and -field EPR (HFEPR), however, has the ability to study such systems effectively. Three complexes, all previously structurally characterized: Na[V(trdta)] · 3H2O, Na[V(edta)(H2O)] · 3H2O, and [V(nta)(H2O)3] · 4H2O (where trdta stands for trimethylenediamine-N,N,N′,N′-tetraacetate and nta stands for nitrilotriacetate) were studied by HFEPR. All the investigated complexes produced HFEPR responses both in the solid state, and in aqueous solution, but those of [V(nta)(H2O)3] · 4H2O were poorly interpretable. Analysis of multi-frequency HFEPR spectra yielded a set of spin Hamiltonian parameters (including axial and rhombic zfs parameters: D and E, respectively) for these first two complexes as solids: Na[V(trdta)] · 3H2O: D = 5.60 cm-1, E = 0.85 cm-1, g = 1.95; Na[V(edta)(H2O)] · 3H2O: D = 1.4 cm-1, E = 0.14 cm-1, g = 1.97. Spectra in frozen solution yielded similar parameters and showed multiple species in the case of the trdta complex, which are the consequence of the flexibility of this ligand. The EPR spectra obtained in frozen aqueous solution are the first, to our knowledge, of V(III) in solution in general and show the applicability of HFEPR to these systems. In combination with very insightful previous studies of the electronic absorption of these complexes which provided ligand-field parameters, it has been possible to describe the electronic structure of V(III) in [V(trdta)]- and [V(edta)(H2O)]-; the quality of data for [V(nta)(H2O)3] does not permit analysis. Qualitatively, six-coordinate V(III) complexes with O,N donor atoms show no electronic absorption band in the NIR region, and exhibit relatively large magnitude zfs (D ≥ 5 cm-1), while analogous seven-coordinate complexes do have a NIR absorption band and show relatively small magnitude zfs (D < 2 cm-1).",
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Aminocarboxylate complexes of vanadium(III) : Electronic structure investigation by high-frequency and -field electron paramagnetic resonance spectroscopy. / Telser, Joshua; Wu, Chi Chin; Chen, Kun Yuan; Hsu, Hua Fen; Smirnov, Dmitry; Ozarowski, Andrew; Krzystek, J.

In: Journal of Inorganic Biochemistry, Vol. 103, No. 4, 01.04.2009, p. 487-495.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Aminocarboxylate complexes of vanadium(III)

T2 - Electronic structure investigation by high-frequency and -field electron paramagnetic resonance spectroscopy

AU - Telser, Joshua

AU - Wu, Chi Chin

AU - Chen, Kun Yuan

AU - Hsu, Hua Fen

AU - Smirnov, Dmitry

AU - Ozarowski, Andrew

AU - Krzystek, J.

PY - 2009/4/1

Y1 - 2009/4/1

N2 - Aminocarboxylate complexes of vanadium(III) are of interest as models for biologically and medicinally relevant forms of this interesting and somewhat neglected ion. The V(III) ion is paramagnetic, but not readily suited to conventional EPR, due to its integer-spin ground state (S = 1) and associated large zero-field splitting (zfs). High-frequency and -field EPR (HFEPR), however, has the ability to study such systems effectively. Three complexes, all previously structurally characterized: Na[V(trdta)] · 3H2O, Na[V(edta)(H2O)] · 3H2O, and [V(nta)(H2O)3] · 4H2O (where trdta stands for trimethylenediamine-N,N,N′,N′-tetraacetate and nta stands for nitrilotriacetate) were studied by HFEPR. All the investigated complexes produced HFEPR responses both in the solid state, and in aqueous solution, but those of [V(nta)(H2O)3] · 4H2O were poorly interpretable. Analysis of multi-frequency HFEPR spectra yielded a set of spin Hamiltonian parameters (including axial and rhombic zfs parameters: D and E, respectively) for these first two complexes as solids: Na[V(trdta)] · 3H2O: D = 5.60 cm-1, E = 0.85 cm-1, g = 1.95; Na[V(edta)(H2O)] · 3H2O: D = 1.4 cm-1, E = 0.14 cm-1, g = 1.97. Spectra in frozen solution yielded similar parameters and showed multiple species in the case of the trdta complex, which are the consequence of the flexibility of this ligand. The EPR spectra obtained in frozen aqueous solution are the first, to our knowledge, of V(III) in solution in general and show the applicability of HFEPR to these systems. In combination with very insightful previous studies of the electronic absorption of these complexes which provided ligand-field parameters, it has been possible to describe the electronic structure of V(III) in [V(trdta)]- and [V(edta)(H2O)]-; the quality of data for [V(nta)(H2O)3] does not permit analysis. Qualitatively, six-coordinate V(III) complexes with O,N donor atoms show no electronic absorption band in the NIR region, and exhibit relatively large magnitude zfs (D ≥ 5 cm-1), while analogous seven-coordinate complexes do have a NIR absorption band and show relatively small magnitude zfs (D < 2 cm-1).

AB - Aminocarboxylate complexes of vanadium(III) are of interest as models for biologically and medicinally relevant forms of this interesting and somewhat neglected ion. The V(III) ion is paramagnetic, but not readily suited to conventional EPR, due to its integer-spin ground state (S = 1) and associated large zero-field splitting (zfs). High-frequency and -field EPR (HFEPR), however, has the ability to study such systems effectively. Three complexes, all previously structurally characterized: Na[V(trdta)] · 3H2O, Na[V(edta)(H2O)] · 3H2O, and [V(nta)(H2O)3] · 4H2O (where trdta stands for trimethylenediamine-N,N,N′,N′-tetraacetate and nta stands for nitrilotriacetate) were studied by HFEPR. All the investigated complexes produced HFEPR responses both in the solid state, and in aqueous solution, but those of [V(nta)(H2O)3] · 4H2O were poorly interpretable. Analysis of multi-frequency HFEPR spectra yielded a set of spin Hamiltonian parameters (including axial and rhombic zfs parameters: D and E, respectively) for these first two complexes as solids: Na[V(trdta)] · 3H2O: D = 5.60 cm-1, E = 0.85 cm-1, g = 1.95; Na[V(edta)(H2O)] · 3H2O: D = 1.4 cm-1, E = 0.14 cm-1, g = 1.97. Spectra in frozen solution yielded similar parameters and showed multiple species in the case of the trdta complex, which are the consequence of the flexibility of this ligand. The EPR spectra obtained in frozen aqueous solution are the first, to our knowledge, of V(III) in solution in general and show the applicability of HFEPR to these systems. In combination with very insightful previous studies of the electronic absorption of these complexes which provided ligand-field parameters, it has been possible to describe the electronic structure of V(III) in [V(trdta)]- and [V(edta)(H2O)]-; the quality of data for [V(nta)(H2O)3] does not permit analysis. Qualitatively, six-coordinate V(III) complexes with O,N donor atoms show no electronic absorption band in the NIR region, and exhibit relatively large magnitude zfs (D ≥ 5 cm-1), while analogous seven-coordinate complexes do have a NIR absorption band and show relatively small magnitude zfs (D < 2 cm-1).

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