Field-Assisted Slow Magnetic Relaxation in a Six-Coordinate Co(II)-Co(III) Complex with Large Negative Anisotropy

Elena A. Buvaylo, Vladimir N. Kokozay, Olga Yu Vassilyeva, Brian W. Skelton, Andrew Ozarowski, Ján Titiš, Beáta Vranovičová, Roman Boča

Research output: Contribution to journalArticle

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Abstract

The reaction of Co(CH3COO)2·4H2O with the Schiff base ligand LH4 derived from o-vanillin and tris(hydroxymethyl)aminomethane produces the dinuclear mixed-valence complex [CoIICoIII(LH2)2(CH3COO)(H2O)](H2O)3 (1), which has been investigated using IR spectroscopy, X-ray crystallography, temperature-dependent magnetic susceptibility, magnetization, HFEPR spectroscopy, and ac susceptibility measurements at various frequencies, temperatures, and external magnetic fields. The structure of 1 consists of neutral molecules in which two cobalt ions with distorted octahedral geometries, CoIIO6 and CoIIIN2O4, are bridged by two deprotonated -CH2O- groups of the two LH2 2- ligands. 1 completes a series with Cl, Br, NO3, and NCS anions published before by different authors. Low-temperature HFEPR measurements reveal that the ground electronic state of the Co(II) center in 1 is a highly anisotropic Kramers doublet; the effective g values of 7.18, 2.97, and 1.96 are frequency-independent over the frequency ranges 200-630, 200-406, and 200-300 GHz for the highest, intermediate, and lowest geff values, respectively. The two lower values were not seen at higher frequencies because the magnetic field was not high enough. Temperature-dependent magnetic susceptibility and field-dependent magnetization data confirm high magnetic anisotropy of the easy axis type. Complex 1 behaves as a single-ion magnet under a small applied external field and demonstrates two relaxation modes that strongly depend on the applied static dc field. The observation of multiple relaxation pathways clearly distinguishes 1 from the Cl and Br analogues.

Original languageEnglish
Pages (from-to)6999-7009
Number of pages11
JournalInorganic Chemistry
Volume56
Issue number12
DOIs
Publication statusPublished - 19 Jun 2017

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Magnetic relaxation
magnetic relaxation
Anisotropy
Magnetic fields
Magnetic susceptibility
magnetic permeability
anisotropy
Magnetization
magnetic fields
Ions
Ligands
magnetization
ligands
Tromethamine
Schiff Bases
Magnetic anisotropy
X ray crystallography
Electronic states
Cobalt
Temperature measurement

Cite this

Buvaylo, Elena A. ; Kokozay, Vladimir N. ; Vassilyeva, Olga Yu ; Skelton, Brian W. ; Ozarowski, Andrew ; Titiš, Ján ; Vranovičová, Beáta ; Boča, Roman. / Field-Assisted Slow Magnetic Relaxation in a Six-Coordinate Co(II)-Co(III) Complex with Large Negative Anisotropy. In: Inorganic Chemistry. 2017 ; Vol. 56, No. 12. pp. 6999-7009.
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title = "Field-Assisted Slow Magnetic Relaxation in a Six-Coordinate Co(II)-Co(III) Complex with Large Negative Anisotropy",
abstract = "The reaction of Co(CH3COO)2·4H2O with the Schiff base ligand LH4 derived from o-vanillin and tris(hydroxymethyl)aminomethane produces the dinuclear mixed-valence complex [CoIICoIII(LH2)2(CH3COO)(H2O)](H2O)3 (1), which has been investigated using IR spectroscopy, X-ray crystallography, temperature-dependent magnetic susceptibility, magnetization, HFEPR spectroscopy, and ac susceptibility measurements at various frequencies, temperatures, and external magnetic fields. The structure of 1 consists of neutral molecules in which two cobalt ions with distorted octahedral geometries, CoIIO6 and CoIIIN2O4, are bridged by two deprotonated -CH2O- groups of the two LH2 2- ligands. 1 completes a series with Cl, Br, NO3, and NCS anions published before by different authors. Low-temperature HFEPR measurements reveal that the ground electronic state of the Co(II) center in 1 is a highly anisotropic Kramers doublet; the effective g values of 7.18, 2.97, and 1.96 are frequency-independent over the frequency ranges 200-630, 200-406, and 200-300 GHz for the highest, intermediate, and lowest geff values, respectively. The two lower values were not seen at higher frequencies because the magnetic field was not high enough. Temperature-dependent magnetic susceptibility and field-dependent magnetization data confirm high magnetic anisotropy of the easy axis type. Complex 1 behaves as a single-ion magnet under a small applied external field and demonstrates two relaxation modes that strongly depend on the applied static dc field. The observation of multiple relaxation pathways clearly distinguishes 1 from the Cl and Br analogues.",
author = "Buvaylo, {Elena A.} and Kokozay, {Vladimir N.} and Vassilyeva, {Olga Yu} and Skelton, {Brian W.} and Andrew Ozarowski and J{\'a}n Titiš and Be{\'a}ta Vranovičov{\'a} and Roman Boča",
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Buvaylo, EA, Kokozay, VN, Vassilyeva, OY, Skelton, BW, Ozarowski, A, Titiš, J, Vranovičová, B & Boča, R 2017, 'Field-Assisted Slow Magnetic Relaxation in a Six-Coordinate Co(II)-Co(III) Complex with Large Negative Anisotropy' Inorganic Chemistry, vol. 56, no. 12, pp. 6999-7009. https://doi.org/10.1021/acs.inorgchem.7b00605

Field-Assisted Slow Magnetic Relaxation in a Six-Coordinate Co(II)-Co(III) Complex with Large Negative Anisotropy. / Buvaylo, Elena A.; Kokozay, Vladimir N.; Vassilyeva, Olga Yu; Skelton, Brian W.; Ozarowski, Andrew; Titiš, Ján; Vranovičová, Beáta; Boča, Roman.

In: Inorganic Chemistry, Vol. 56, No. 12, 19.06.2017, p. 6999-7009.

Research output: Contribution to journalArticle

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T1 - Field-Assisted Slow Magnetic Relaxation in a Six-Coordinate Co(II)-Co(III) Complex with Large Negative Anisotropy

AU - Buvaylo, Elena A.

AU - Kokozay, Vladimir N.

AU - Vassilyeva, Olga Yu

AU - Skelton, Brian W.

AU - Ozarowski, Andrew

AU - Titiš, Ján

AU - Vranovičová, Beáta

AU - Boča, Roman

PY - 2017/6/19

Y1 - 2017/6/19

N2 - The reaction of Co(CH3COO)2·4H2O with the Schiff base ligand LH4 derived from o-vanillin and tris(hydroxymethyl)aminomethane produces the dinuclear mixed-valence complex [CoIICoIII(LH2)2(CH3COO)(H2O)](H2O)3 (1), which has been investigated using IR spectroscopy, X-ray crystallography, temperature-dependent magnetic susceptibility, magnetization, HFEPR spectroscopy, and ac susceptibility measurements at various frequencies, temperatures, and external magnetic fields. The structure of 1 consists of neutral molecules in which two cobalt ions with distorted octahedral geometries, CoIIO6 and CoIIIN2O4, are bridged by two deprotonated -CH2O- groups of the two LH2 2- ligands. 1 completes a series with Cl, Br, NO3, and NCS anions published before by different authors. Low-temperature HFEPR measurements reveal that the ground electronic state of the Co(II) center in 1 is a highly anisotropic Kramers doublet; the effective g values of 7.18, 2.97, and 1.96 are frequency-independent over the frequency ranges 200-630, 200-406, and 200-300 GHz for the highest, intermediate, and lowest geff values, respectively. The two lower values were not seen at higher frequencies because the magnetic field was not high enough. Temperature-dependent magnetic susceptibility and field-dependent magnetization data confirm high magnetic anisotropy of the easy axis type. Complex 1 behaves as a single-ion magnet under a small applied external field and demonstrates two relaxation modes that strongly depend on the applied static dc field. The observation of multiple relaxation pathways clearly distinguishes 1 from the Cl and Br analogues.

AB - The reaction of Co(CH3COO)2·4H2O with the Schiff base ligand LH4 derived from o-vanillin and tris(hydroxymethyl)aminomethane produces the dinuclear mixed-valence complex [CoIICoIII(LH2)2(CH3COO)(H2O)](H2O)3 (1), which has been investigated using IR spectroscopy, X-ray crystallography, temperature-dependent magnetic susceptibility, magnetization, HFEPR spectroscopy, and ac susceptibility measurements at various frequencies, temperatures, and external magnetic fields. The structure of 1 consists of neutral molecules in which two cobalt ions with distorted octahedral geometries, CoIIO6 and CoIIIN2O4, are bridged by two deprotonated -CH2O- groups of the two LH2 2- ligands. 1 completes a series with Cl, Br, NO3, and NCS anions published before by different authors. Low-temperature HFEPR measurements reveal that the ground electronic state of the Co(II) center in 1 is a highly anisotropic Kramers doublet; the effective g values of 7.18, 2.97, and 1.96 are frequency-independent over the frequency ranges 200-630, 200-406, and 200-300 GHz for the highest, intermediate, and lowest geff values, respectively. The two lower values were not seen at higher frequencies because the magnetic field was not high enough. Temperature-dependent magnetic susceptibility and field-dependent magnetization data confirm high magnetic anisotropy of the easy axis type. Complex 1 behaves as a single-ion magnet under a small applied external field and demonstrates two relaxation modes that strongly depend on the applied static dc field. The observation of multiple relaxation pathways clearly distinguishes 1 from the Cl and Br analogues.

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U2 - 10.1021/acs.inorgchem.7b00605

DO - 10.1021/acs.inorgchem.7b00605

M3 - Article

VL - 56

SP - 6999

EP - 7009

JO - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

IS - 12

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