Relationship between the Thermally Induced Reorientations of Aromatic Solvate Molecules in Cu(hfac)2鈥揘itroxide Breathing Crystals and the Character of the Magnetic Anomaly

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• 作者：Galina V. Romanenko ; Ksenia Yu. Maryunina ; Artem S. Bogomyakov ; Renad Z. Sagdeev ; Victor I. Ovcharenko
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：July 18, 2011
• 年：2011
• 卷：50
• 期：14
• 页码：6597-6609
• 全文大小：1323K
• 年卷期：v.50,no.14(July 18, 2011)
• ISSN：1520-510X

文摘

A new group of 鈥渂reathing鈥?crystals has been synthesized. These are aromatic solvates of the copper(II) hexafluoroacetylacetonate complex with spin-labeled pyrazole Cu(hfac)₂L路0.5Solv, where L is 2-(1-butyl-1H-pyrazol-4-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl and Solv is benzene, toluene, ethylbenzene, propylbenzene, butylbenzene, styrene, o-xylene, m-xylene, p-xylene, 1,4-bis(trifluoromethyl)benzene, 1-methyl-4-ethylbenzene, 1-methyl-4-vinylbenzene, 1,4-diethylbenzene, 1,2,3-trimethylbenzene, or 1,2,4-trimethylbenzene. The main feature of Cu(hfac)₂L路0.5Solv single crystals is their remarkable mechanical stability and ability to undergo thermally induced structural rearrangements accompanied by spin-crossover-like phenomena. The structures of Cu(hfac)₂L路0.5Solv solvates are similar and based on mutually parallel {Cu(hfac)₂L}_{鈭?/sub> heterospin chains with a 鈥渉ead-to-head鈥?motif. The localization of voids with guest molecules being the same in all crystals, the temperature dependence of the effective magnetic moment (渭eff) for Cu(hfac)2L路0.5Solv is determined by the structure of the guest molecules, along which the polymer chains are 鈥済liding鈥?when the temperature changes. When the temperature decreased from 300 to 100鈥?0 K, 渭eff decreased, abruptly or gradually, from 2.7鈥?.4 to 1.8 尾 for the majority of Cu(hfac)2L路0.5Solv except the solvates with benzene, toluene, and 1,4-bis(trifluoromethyl)benzene. When Cu(hfac)2L路0.5C6H6 and Cu(hfac)2L路0.5CH3鈥揅6H5 were cooled to 50 K, 渭eff decreased to 2.1鈥?.2 尾. When Cu(hfac)2L路0.5(1,4-(CF3)2鈥揅6H4) was cooled to 50 K, 渭eff initially decreased from 2.7 to 1.9 尾 and then abruptly increased to 2.4 尾. A single-crystal X-ray diffraction analysis of each solvate within a temperature range wider than the range of magnetic anomaly temperatures revealed a complex interrelated dynamics of the aromatic solvent guest molecules and heterospin chains. The dynamics largely depended on the orientation of the solvent guest molecules relative to the polymer chains. An analysis of the thermally induced phase transformations revealed a relationship between the structural rearrangement of Cu(hfac)2L路0.5Solv and the form of the magnetic anomaly on the 渭eff(T) curve and between the structural rearrangement of the solvate and the temperature of the magnetic effect.}