Shift of stereochemical nonrigidity from coordination units to polymethylene fragments in heterospin copper(II) hexafluoroacetylacetonate complexes with nitronyl nitroxide biradicals

Романенко, Г. В.; Толстиков, С. Е.; Tretyakov, Evgeny V.; Fokin, S. V.; Ikorskiǐ, V. N.; Овчаренко, В. И.

doi:10.1007/s11172-007-0279-6

Cited by 6 publications

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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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