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.
N1 - Funding Information:
H.-F.H., C.-C.W., and K.-Y.C. gratefully acknowledge the National Science Council in Taiwan for funding this work (NSC 96-2113-M-006-011). HFEPR studies were supported by the National High Magnetic Field Laboratory, which is funded by the NSF through Cooperative Agreement DMR 0654118, the State of Florida, and the DOE. The 25-T resistive magnet was funded by the W.M. Keck Foundation. J.T. and J.K. acknowledge NHMFL IHRP grant 5062. We thank Prof. Dr. Thomas Schönherr, Heinrich-Heine-University of Düsseldorf, Germany, for providing a reference and for many helpful discussions.
PY - 2009/4
Y1 - 2009/4
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).
UR - http://www.scopus.com/inward/record.url?scp=62349117802&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=62349117802&partnerID=8YFLogxK
U2 - 10.1016/j.jinorgbio.2009.01.016
DO - 10.1016/j.jinorgbio.2009.01.016
M3 - Article
C2 - 19269689
AN - SCOPUS:62349117802
SN - 0162-0134
VL - 103
SP - 487
EP - 495
JO - Journal of Inorganic Biochemistry
JF - Journal of Inorganic Biochemistry
IS - 4
ER -