Abstract
New heterospin complexes of Cu(hfac)2 (hfac, hexafluoroacetylacetonate) with pyrazole-substituted nitronyl nitroxides have been found that in the solid state exhibit thermally induced spin transitions analogous to spin crossover. For the first complex, [Cu(hfac)2Li-Pr], at room temperature, the Cu-OL distances, where OL is the oxygen atom of the nitroxyl group, are very short (2.143 Å). This leads to a strong antiferromagnetic exchange (∼-120 cm-1) in the > N-.O-Cu2+-O.-N< exchange clusters. The CuO6 coordination units formed by four O atoms of the two hfac anions and by the nitroxyl O atoms of the two bridging nitroxides have a rare form of flattened octahedra, transformed at low temperatures into elongated octahedra with shorter CU-OL distances (2.143 Å → 2.002 Å) and two longer Cu-Ohfac distances (2.130 Å → 2.293 Å). For the second complex, [Cu(hfac)2LBU·0.5C6H14], unusual low temperature structural dynamics of heterospin systems have been found. It is characterized by the formation of two types of CuO6 unit. The axial Cu-OL distances are lengthened in one unit (2.250 Å → 2.347 Å) and shortened in the other (2.250 Å → 2.006 Å). This leads to a sophisticated μeff(T) dependence with μeff drastically decreased at 163 K as a result of full coupling of two spins in half of all >N-.O-Cu2+-O.-N< exchange clusters and to a shift from antiferromagnetic to ferromagnetic exchange in the other half.
| Original language | English |
|---|---|
| Pages (from-to) | 1107-1115 |
| Number of pages | 9 |
| Journal | Molecular Physics |
| Volume | 100 |
| Issue number | 8 |
| DOIs | |
| Publication status | Published - 20 Apr 2002 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Biophysics
- Molecular Biology
- Condensed Matter Physics
- Physical and Theoretical Chemistry
Cite this
Unusual spin transitions. / Ovcharenko, V. I.; Fokin, S. V.; Romanenko, G. V.; Ikorskii, V. N.; Tretyakov, E. V.; Vasilevsky, S. F.; Sagdeev, R. Z.
In: Molecular Physics, Vol. 100, No. 8, 20.04.2002, p. 1107-1115.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Unusual spin transitions
AU - Ovcharenko, V. I.
AU - Fokin, S. V.
AU - Romanenko, G. V.
AU - Ikorskii, V. N.
AU - Tretyakov, E. V.
AU - Vasilevsky, S. F.
AU - Sagdeev, R. Z.
PY - 2002/4/20
Y1 - 2002/4/20
N2 - New heterospin complexes of Cu(hfac)2 (hfac, hexafluoroacetylacetonate) with pyrazole-substituted nitronyl nitroxides have been found that in the solid state exhibit thermally induced spin transitions analogous to spin crossover. For the first complex, [Cu(hfac)2Li-Pr], at room temperature, the Cu-OL distances, where OL is the oxygen atom of the nitroxyl group, are very short (2.143 Å). This leads to a strong antiferromagnetic exchange (∼-120 cm-1) in the > N-.O-Cu2+-O.-N< exchange clusters. The CuO6 coordination units formed by four O atoms of the two hfac anions and by the nitroxyl O atoms of the two bridging nitroxides have a rare form of flattened octahedra, transformed at low temperatures into elongated octahedra with shorter CU-OL distances (2.143 Å → 2.002 Å) and two longer Cu-Ohfac distances (2.130 Å → 2.293 Å). For the second complex, [Cu(hfac)2LBU·0.5C6H14], unusual low temperature structural dynamics of heterospin systems have been found. It is characterized by the formation of two types of CuO6 unit. The axial Cu-OL distances are lengthened in one unit (2.250 Å → 2.347 Å) and shortened in the other (2.250 Å → 2.006 Å). This leads to a sophisticated μeff(T) dependence with μeff drastically decreased at 163 K as a result of full coupling of two spins in half of all >N-.O-Cu2+-O.-N< exchange clusters and to a shift from antiferromagnetic to ferromagnetic exchange in the other half.
AB - New heterospin complexes of Cu(hfac)2 (hfac, hexafluoroacetylacetonate) with pyrazole-substituted nitronyl nitroxides have been found that in the solid state exhibit thermally induced spin transitions analogous to spin crossover. For the first complex, [Cu(hfac)2Li-Pr], at room temperature, the Cu-OL distances, where OL is the oxygen atom of the nitroxyl group, are very short (2.143 Å). This leads to a strong antiferromagnetic exchange (∼-120 cm-1) in the > N-.O-Cu2+-O.-N< exchange clusters. The CuO6 coordination units formed by four O atoms of the two hfac anions and by the nitroxyl O atoms of the two bridging nitroxides have a rare form of flattened octahedra, transformed at low temperatures into elongated octahedra with shorter CU-OL distances (2.143 Å → 2.002 Å) and two longer Cu-Ohfac distances (2.130 Å → 2.293 Å). For the second complex, [Cu(hfac)2LBU·0.5C6H14], unusual low temperature structural dynamics of heterospin systems have been found. It is characterized by the formation of two types of CuO6 unit. The axial Cu-OL distances are lengthened in one unit (2.250 Å → 2.347 Å) and shortened in the other (2.250 Å → 2.006 Å). This leads to a sophisticated μeff(T) dependence with μeff drastically decreased at 163 K as a result of full coupling of two spins in half of all >N-.O-Cu2+-O.-N< exchange clusters and to a shift from antiferromagnetic to ferromagnetic exchange in the other half.
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U2 - 10.1080/00268970110109510
DO - 10.1080/00268970110109510
M3 - Article
AN - SCOPUS:0037140505
VL - 100
SP - 1107
EP - 1115
JO - Molecular Physics
JF - Molecular Physics
SN - 0026-8976
IS - 8
ER -