Spin-Crossover Behaviors Based on Intermolecular Interactions for Cobalt(II) Complexes with Long Alkyl Chains
Spin-Crossover Behaviors Based on Intermolecular Interactions for Cobalt(II) Complexes with Long Alkyl Chains
复制标题
DOI：
10.1002/ejic.201101040
复制
发表时间：
2012-06
影响因子：
2.3
通讯作者：
Y. Komatsu;Kazuya Katô;Yuuki Yamamoto;Hidenobu Kamihata;Young Hoon Lee;A. Fuyuhiro;S. Kawata;S. Hayami
中科院分区：
文献类型：
--
作者：
Y. Komatsu;Kazuya Katô;Yuuki Yamamoto;Hidenobu Kamihata;Young Hoon Lee;A. Fuyuhiro;S. Kawata;S. Hayami
合成了一个新的基于三联吡啶（terpy）的自旋交叉钴（II）配合物家族[Co(HO-Cn-terpy)2](BF4)2 [n = 6(1), 8(2), 10(3), 12(4)和14(5)]，该配合物在三联吡啶骨架上具有羟基附加的长烷基链，并通过x射线结构分析和温度相关磁化率对其进行了表征。在固体状态下，化合物1·H2O、4和5·H2O在三斜的P空间基上结晶，其中心的钴（II）离子与来自两个三联吡啶单元的6个氮原子配位，形成伪八面体对称。在1·H2O的情况下，其中一个末端羟基取代基参与了与水分子的氢键。另一方面，对于化合物4，两个末端羟基单元与BF4 -阴离子形成短的分子间接触。1和2的温度相关磁行为表现为逐渐的自旋交叉，而3和4表现为突然的自旋转变，具有宽热滞回线（ΔT = 21 K, T1/2 = 316 K, T1/2 = 295 K）， ΔT = 40 K, T1/2 = 348 K, T1/2 = 308 K)， 5表现为“反向自旋转变”（ΔT = 17 K, T1/2 = 214 K, T1/2 = 231 K）。化合物3和4通过扣紧效应和氢键形成比1和2更强的分子间相互作用。通过对末端带有羟基的长烷基链化合物的磁性行为进行比较，发现末端带有羟基的长烷基链可以诱导分子间更强的相互作用。然而，5·H2O的反阴离子有许多短接触，但长烷基链的热运动是可以预期的。化合物5表现出由结构相变引起的“反向自旋转变”。
A new family of terpyridine (terpy)-based spin-crossover cobalt(II) complexes, [Co(HO–Cn-terpy)2](BF4)2 [n = 6 (1), 8 (2), 10 (3), 12 (4), and 14 (5)] that possesses a hydroxy-appended long alkyl chain present on the terpyridine skeleton was synthesized and characterized by X-ray structure analysis and temperature-dependent magnetic susceptibility. In the solid state, the compounds 1·H2O, 4, and 5·H2O were crystallized in the triclinic P space groups, and their central cobalt(II) ion was coordinated by six nitrogen atoms from two terpyridine units to form a pseudo-octahedral symmetry. In the case of 1·H2O, one of the terminal hydroxy substituents was involved in hydrogen bonding with a water molecule. For compound 4, on the other hand, both of terminal hydroxy units form a short intermolecular contact with the BF4– anion. The temperature-dependent magnetic behavior of 1 and 2 showed a gradual spin crossover, whereas 3 and 4 revealed an abrupt spin transition with a wide thermal hysteresis loop (ΔT = 21 K, T1/2 = 316 K, and T1/2 = 295 K for 3; ΔT = 40 K, T1/2 = 348 K, and T1/2 = 308 K for 4), and 5 exhibits “reverse spin transition” (ΔT = 17 K, T1/2 = 214 K, andT1/2 = 231 K). It has been suggested that compounds 3 and 4 form stronger intermolecular interactions through the fastener effect and hydrogen bonding than 1 and 2. On the basis of a comparison of the resulting magnetic behaviors of the compounds that contain long alkyl chains with a hydroxy group at the end, it was found that the long alkyl chains with the terminal hydroxy group could induce stronger intermolecular interactions between molecules. However, there are many short contacts through the counteranions for 5·H2O, but thermal motion of the long alkyl chains can be expected. Compound 5 exhibits “reverse spin transition” induced by a structural phase transition.