Unusual spin transitions

Овчаренко, В. И.; Fokin, S. V.; Романенко, Г. В.; Ikorskiǐ, V. N.; Tretyakov, Evgeny V.; Vasilevsky, S. F.; Sagdeev, R. Z.

doi:10.1080/00268970110109510

Cited by 58 publications

(52 citation statements)

References 6 publications

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“…9.22, left column) show a different character of magnetic anomalies for each compound. 20,[42][43][44] Typically, at T < 50 K, all spin-triads are already in the strongly coupled state S = 1 / 2 (μ eff ≈ 1.8 β), and the magnetic behavior at lower temperatures is governed by inter-cluster exchange interactions. Two of the compounds, [Cu(hfac) 2 L n-Bu ]·0.5C 7 H 16 and [Cu(hfac) 2 L n-Bu ]·0.5C 8 H 18 ( Fig.…”

Section: Epr Measurement Of Dipole-dipole Interaction and Inter-clustmentioning

confidence: 99%

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Breathing Crystals from Copper Nitroxyl Complexes

Овчаренко

Bagryanskaya

2013

Spin‐Crossover Materials

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IntroductionCoordination chemistry of transition metals with stable nitroxides is one of the actively developed branches of modern chemistry which is an important tool in solving the problems of molecular magnetism. The results of studies of metal complexes with nitroxides and their synthesis have been reported from various viewpoints in monographs and reviews. 1-19 Studies of heterospin compounds have led to the creation of new classes of compounds with new combinations of physical characteristics. 19 These include breathing crystals based on Cu(II) coordination compounds with stable nitroxides. Interest in these compounds has recently developed enormously and their number has increased dramatically. This prompted us to summarize data on their magnetostructural correlations. The discussion concentrated on Cu(II) hexafluoroacetylacetonate complexes [Cu(hfac) 2 ] with pyrazolyl-substituted nitronyl nitroxides. These compounds have been studied for more than 10 years 20, 21 and are well defined. The first part of the chapter summarizes the main features of breathing crystals, obtained using X-ray and magnetic measurements, and the second part overviews the results of EPR. EPR spectroscopy as applied to breathing crystals has a number of peculiarities which demands the development of new approaches. EPR study of breathing crystals is very informative, even though the exchange interaction in nitroxide-copper-nitroxide clusters significantly exceeds the value of Zeeman interaction.A very interesting characteristic of the complexes is the similarity of their magnetic properties to spintransitions in classical systems based on the temperature dependence of the effective magnetic moment (μ eff ). Note that the classical spin-crossover 22-35 is absolutely impossible in Cu(II) complexes with diamagnetic ligands, which contain only d 9 paramagnetic centers. The main distinction of spin-transitions in Cu(II) Spin-Crossover Materials: Properties and Applications, First Edition. Edited by Malcolm A. Halcrow.

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Section: Epr Measurement Of Dipole-dipole Interaction and Inter-clustmentioning

confidence: 99%

“…19,38,43,44 They had a valuable property: the single crystals of the complexes did not crack in the temperature range of the structural phase transition and the ensuing magnetic transition. Due to the mechanical plasticity of these compounds, these processes were regarded as single-crystal-to-single-crystal phase transitions in the majority of cases.…”

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confidence: 99%

Breathing Crystals from Copper Nitroxyl Complexes

Овчаренко

Bagryanskaya

2013

Spin‐Crossover Materials

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“…As a result, a family of heterospin complexes with magnetic properties similar to spin crossover was created. 215,216 The single crystals generally did not crack after the temperature range of the structural transition and the ensuing magnetic transition. The structure was determined for all heterospin complexes and their solid solutions at temperatures before and after the magnetic transition, which provided a unique opportunity for the observation of structure dynamics in the range of the phase transition for these systems.…”

Section: Breathing Crystalsmentioning

confidence: 99%

Metal–Nitroxide Complexes: Synthesis and Magnetostructural Correlations

Овчаренко¹

2010

Stable Radicals

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IntroductionInteractions between the paramagnetic ions of transition metals and stable radicals are convenient and effective methods for the synthesis of multispin molecules. These metal-nitroxide systems are often called heterospin systems because they contain paramagnetic centers with both d (or f) odd electrons and centers with p electrons. Paramagnetic centers can differ in the electron spin, g factor, the character of electron spin density delocalization, and heat capacity. The presence of several paramagnetic centers in heterospin molecules has stirred growing interest in their magnetic properties because these compounds are convenient objects for studying the subtle peculiarities of exchange interactions and revealing valuable magnetostructural correlations. That is why coordination chemistry of transition metals with stable nitroxides is an actively developing direction in modern chemistry that contributes to problem solving in the field of molecular magnetism. The results of studies on the synthesis and properties of metal complexes with nitroxides have been considered from different viewpoints and at different times in many monographs and reviews. 1 -19 Importantly, this approach offers the potential for control over the structure of the designed heterospin molecule and the character of interactions between the odd electrons of paramagnetic centers, which is necessary for constructing justifiable magnetostructural correlations. This is one of the factors responsible for the continuous growth of the number of new metal-nitroxide complexes. The Cambridge Structural Database alone contains more than one thousand structurally defined metal-nitroxide systems. 20 Therefore, currently it is impossible and not necessary to collect all available literature data on the synthesis and properties of metal-nitroxide systems in one publication. In any account, a comprehensive review of this kind will already have become incomplete by the time of its publication because new heterospin compounds based on transition metal compounds with nitroxides are being added daily to the list. However, the Stable Radicals: Fundamentals and Applied Aspects of Odd-Electron CompoundsEdited by Robin G. Hicks

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“…9 Recently rather different SCO transitions were found in the chain-polymer compounds Cu(II) with nitroxides. 10 These compounds contain chains of the exchange clusters with two or three spins. The exchange clusters contain Cu 2+ , ligands, and some organic radicals.…”

Section: Introductionmentioning

confidence: 99%

Interplay between lattice, orbital, and magnetic degrees of freedom in the chain-polymer Cu(II) breathing crystals

et al. 2013

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The chain-polymer Cu(II) "breathing crystals" C 21 H 19 CuF 12 N 4 O 6 were studied using the x-ray diffraction and ab initio band structure calculations. We show that the crystal structure modification at T = 146 K, associated with the spin crossover transition, induces the changes of the orbital order in half of the Cu sites. This in turn results in the switch of the magnetic interaction sign in accordance with the Goodenough-Kanamori-Andersen theory of the coupling between the orbital and spin degrees of freedom.

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Unusual spin transitions

Cited by 58 publications

References 6 publications

Breathing Crystals from Copper Nitroxyl Complexes

Breathing Crystals from Copper Nitroxyl Complexes

Metal–Nitroxide Complexes: Synthesis and Magnetostructural Correlations

Interplay between lattice, orbital, and magnetic degrees of freedom in the chain-polymer Cu(II) breathing crystals

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