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Determination of the number of unpaired electrons in metal-complexes: a comparison between the Evans' method and susceptometer results

Klaartje De Buysser (UGent) , Gerrit Herman (UGent) , Els Bruneel (UGent) , Serge Hoste (UGent) and Isabel Van Driessche (UGent)
Author
Organization
Abstract
1,4,8,11-tetraazacyclotetradecane (cyclam) is widely known as an ideal ligand for chelating heavy metal ions such as Ni2+ and Cu2+ in aqueous media. In this work the consequences of chelation on the preference for high spin or low spin configuration were investigated for Fe3+, Ni2+, Cu2+ and Ci(3+). Two methods were used to determine the number Of unpaired electrons in the solid and dissolved complex. First the change of magnetic susceptibility of the crystalline powder as a Junction of temperature was measured. In the second case Evans NMR-based method was used to obtain information about the number of unpaired electrons in the dissolved complexes. In some cases, such as Fe3+ and Ni2+, a discrepancy between the two methods was noticed This behaviour is discussed in terms of the preference of the large high spin Ni2+-ion to switch to the smaller low spin Ni2+-ion in the aqueous environment, which better fits the cavity of the ligand in the square planar geometry. The results are influenced by the geometry of the complex, the aggregation state and the dimensions of the ions.
Keywords
low spin, high spin, NMR method, 1, 4, 11-tetraazacyclotetradecane, 8

Citation

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Chicago
De Buysser, Klaartje, Gerrit Herman, Els Bruneel, Serge Hoste, and Isabel Van Driessche. 2005. “Determination of the Number of Unpaired Electrons in Metal-complexes: a Comparison Between the Evans’ Method and Susceptometer Results.” In Measurement 2005, Proceedings, 350–353. Bratislava, Slovakia: Institute of Measurement Science.
APA
De Buysser, K., Herman, G., Bruneel, E., Hoste, S., & Van Driessche, I. (2005). Determination of the number of unpaired electrons in metal-complexes: a comparison between the Evans’ method and susceptometer results. Measurement 2005, Proceedings (pp. 350–353). Presented at the 5th International conference on Measurement (Measurement 2005), Bratislava, Slovakia: Institute of Measurement Science.
Vancouver
1.
De Buysser K, Herman G, Bruneel E, Hoste S, Van Driessche I. Determination of the number of unpaired electrons in metal-complexes: a comparison between the Evans’ method and susceptometer results. Measurement 2005, Proceedings. Bratislava, Slovakia: Institute of Measurement Science; 2005. p. 350–3.
MLA
De Buysser, Klaartje, Gerrit Herman, Els Bruneel, et al. “Determination of the Number of Unpaired Electrons in Metal-complexes: a Comparison Between the Evans’ Method and Susceptometer Results.” Measurement 2005, Proceedings. Bratislava, Slovakia: Institute of Measurement Science, 2005. 350–353. Print.
@inproceedings{405460,
  abstract     = {1,4,8,11-tetraazacyclotetradecane (cyclam) is widely known as an ideal ligand for chelating heavy metal ions such as Ni2+ and Cu2+ in aqueous media. In this work the consequences of chelation on the preference for high spin or low spin configuration were investigated for Fe3+, Ni2+, Cu2+ and Ci(3+). Two methods were used to determine the number Of unpaired electrons in the solid and dissolved complex. First the change of magnetic susceptibility of the crystalline powder as a Junction of temperature was measured. In the second case Evans NMR-based method was used to obtain information about the number of unpaired electrons in the dissolved complexes. In some cases, such as Fe3+ and Ni2+, a discrepancy between the two methods was noticed This behaviour is discussed in terms of the preference of the large high spin Ni2+-ion to switch to the smaller low spin Ni2+-ion in the aqueous environment, which better fits the cavity of the ligand in the square planar geometry. The results are influenced by the geometry of the complex, the aggregation state and the dimensions of the ions.},
  author       = {De Buysser, Klaartje and Herman, Gerrit and Bruneel, Els and Hoste, Serge and Van Driessche, Isabel},
  booktitle    = {Measurement 2005, Proceedings},
  isbn         = {80-967402-8-8},
  language     = {eng},
  location     = {Smolenice, Slovakia},
  pages        = {350--353},
  publisher    = {Institute of Measurement Science},
  title        = {Determination of the number of unpaired electrons in metal-complexes: a comparison between the Evans' method and susceptometer results},
  year         = {2005},
}

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