Vieira Bruno J C, Dias João C, Santos Isabel C, Pereira Laura C J, da Gama Vasco, Waerenborgh João C
Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa , 2695-066 Bobadela LRS, Portugal.
Inorg Chem. 2015 Feb 16;54(4):1354-62. doi: 10.1021/ic502278d. Epub 2015 Jan 29.
The Fe(III) complexes Fe(5-Br-qsal)2Ni(dmit)2·solv with solv = CH2Cl2 (1) and (CH3)2CO (2) were synthesized, and their structural and magnetic properties were studied. While magnetization and Mössbauer spectroscopy data of 1 showed a gradual spin transition, compound 2 evidenced an abrupt transition with a thermal hysteresis of 13 K close to room temperature (T1/2 ↓ ∼273 K and T1/2 ↑ ∼286 K). A similar packing arrangement of segregated layers of cations and anions was found for 1 and 2. In both low-spin, LS, structures there are a large number of short intra- and interchain contacts. This number is lower in the high-spin, HS, phases, particularly in the case of 1. The significant loss of strong π-π interactions in the cationic chains and short contacts in the anionic chains in the HS structure of 1 leads to alternating strong and weak bonds between cations along the cationic chains and the formation of unconnected dimers along the anionic chains. This is consistent with a significant weakening of the extended interactions in 1. On the other hand, in the HS phase of 2 the 3D dimensionality of the short contacts observed in the LS phases is preserved. The effect of distinct solvent molecules on the intermolecular spacings explains the different spin crossover behaviors of the title compounds.
合成了溶剂为二氯甲烷（1）和丙酮（2）的Fe(III)配合物Fe(5-Br-qsal)2Ni(dmit)2·solv，并研究了它们的结构和磁性。虽然1的磁化强度和穆斯堡尔光谱数据显示出逐渐的自旋转变，但化合物2表现出突然转变，在接近室温时具有13 K的热滞回（T1/2↓ ∼273 K和T1/2↑ ∼286 K）。对于1和2，发现阳离子和阴离子的隔离层具有相似的堆积排列。在两种低自旋（LS）结构中，都存在大量短的链内和链间接触。在高自旋（HS）相中，这种接触的数量较少，特别是在1的情况下。在1的HS结构中，阳离子链中强π-π相互作用的显著丧失以及阴离子链中短接触的减少，导致沿阳离子链的阳离子之间交替出现强键和弱键，并沿阴离子链形成未连接的二聚体。这与1中扩展相互作用的显著减弱是一致的。另一方面，在2的HS相中，在LS相中观察到的短接触的三维空间结构得以保留。不同溶剂分子对分子间间距的影响解释了标题化合物不同的自旋交叉行为。
