International Tomography Center, Siberian Branch of the Russian Academy of Sciences, 3A Institutskaya Street, 630090 Novosibirsk, Russia.
Inorg Chem. 2011 Jul 18;50(14):6597-609. doi: 10.1021/ic200444e. Epub 2011 Jun 15.
A new group of "breathing" crystals has been synthesized. These are aromatic solvates of the copper(II) hexafluoroacetylacetonate complex with spin-labeled pyrazole Cu(hfac)(2)L·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)(2)L·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)(2)L·0.5Solv solvates are similar and based on mutually parallel {Cu(hfac)(2)L}(∞) heterospin chains with a "head-to-head" motif. The localization of voids with guest molecules being the same in all crystals, the temperature dependence of the effective magnetic moment (μ(eff)) for Cu(hfac)(2)L·0.5Solv is determined by the structure of the guest molecules, along which the polymer chains are "gliding" when the temperature changes. When the temperature decreased from 300 to 100-50 K, μ(eff) decreased, abruptly or gradually, from 2.7-2.4 to ~1.8 β for the majority of Cu(hfac)(2)L·0.5Solv except the solvates with benzene, toluene, and 1,4-bis(trifluoromethyl)benzene. When Cu(hfac)(2)L·0.5C(6)H(6) and Cu(hfac)(2)L·0.5CH(3)-C(6)H(5) were cooled to 50 K, μ(eff) decreased to ~2.1-2.2 β. When Cu(hfac)(2)L·0.5(1,4-(CF(3))(2)-C(6)H(4)) was cooled to 50 K, μ(eff) initially decreased from ~2.7 to 1.9 β and then abruptly increased to ~2.4 β. 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)(2)L·0.5Solv and the form of the magnetic anomaly on the μ(eff)(T) curve and between the structural rearrangement of the solvate and the temperature of the magnetic effect.
一组新的“呼吸”晶体已经被合成。这些是铜(II)六氟乙酰丙酮配合物与自旋标记吡唑 Cu(hfac)(2)L·0.5Solv 的芳香溶剂化物，其中 L 是 2-(1-丁基-1H-吡唑-4-基)-4,4,5,5-四甲基-4,5-二氢-1H-咪唑-3-氧化物-1-氧基，Solv 是苯、甲苯、乙苯、丙苯、丁苯、苯乙烯、邻二甲苯、间二甲苯、对二甲苯、1,4-双（三氟甲基）苯、1-甲基-4-乙基苯、1-甲基-4-乙烯基苯、1,4-二乙基苯、1,2,3-三甲苯或 1,2,4-三甲苯。Cu(hfac)(2)L·0.5Solv 单晶的主要特点是其显著的机械稳定性和经历热诱导结构重排的能力，伴随着自旋交叉类似现象。Cu(hfac)(2)L·0.5Solv 溶剂化物的结构相似，基于相互平行的{Cu(hfac)(2)L}(∞)杂自旋链，具有“头对头”的基序。在所有晶体中，空位的定位与客体分子相同，因此 Cu(hfac)(2)L·0.5Solv 的有效磁矩 (μ(eff)) 的温度依赖性取决于客体分子的结构，当温度变化时，聚合物链沿着这些结构“滑动”。当温度从 300 降至 100-50 K 时，对于大多数 Cu(hfac)(2)L·0.5Solv（除了苯、甲苯和 1,4-双（三氟甲基）苯的溶剂化物外），μ(eff)从 2.7-2.4 逐渐或急剧下降至1.8 β。当 Cu(hfac)(2)L·0.5C(6)H(6)和 Cu(hfac)(2)L·0.5CH(3)-C(6)H(5)冷却至 50 K 时，μ(eff)下降至2.1-2.2 β。当 Cu(hfac)(2)L·0.5(1,4-(CF(3))(2)-C(6)H(4))冷却至 50 K 时，μ(eff)最初从2.7 下降至 1.9 β，然后急剧增加至2.4 β。在比磁异常温度范围更宽的温度范围内对每个溶剂化物进行单晶 X 射线衍射分析，揭示了芳香溶剂客体分子和杂自旋链之间复杂的相互关联动力学。动力学在很大程度上取决于溶剂客体分子相对于聚合物链的取向。对热诱导相转变的分析揭示了 Cu(hfac)(2)L·0.5Solv 的结构重排与 μ(eff)(T)曲线中磁异常的形式之间以及溶剂化物的结构重排与磁效应的温度之间的关系。
