Ortega-Villar Norma, Thompson Amber L, Muñoz M Carmen, Ugalde-Saldívar Víctor M, Goeta Andrés E, Moreno-Esparza Rafael, Real José A
Institut de Ciencia Molecular/Departament de Química Inorgánica, Universitat de València, Doctor Moliner 50, 46100 Burjassot, Spain.
Chemistry. 2005 Sep 19;11(19):5721-34. doi: 10.1002/chem.200500171.
The mononuclear diamagnetic compound {Fe(bztpen)[N(CN)2]}(PF6)CH3OH (1) (bztpen = N-benzyl-N,N',N'-tris(2-pyridylmethyl)ethylenediamine) has been synthesized and its crystal structure studied. Complex 1 can be considered to be the formal precursor of two new dinuclear, dicyanamide-bridged iron(II) complexes with the generic formula {[(Fe(bztpen)]2[mu-N(CN)2]}(PF6)3 x n H2O (n = 1 (2) or 0 (3)), which have been characterized in the solid state and in solution. In all three complexes, the iron atoms have a distorted [FeN6] octahedral coordination defined by a bztpen ligand and a terminal (1) or a bridging dicyanamide ligand (2 and 3). In the solid state, 2 and 3 can be considered to be molecular isomers that differ by the relative position of the phenyl ring of the two {Fe(bztpen)[N(CN)2]}+ halves (cis and trans, respectively). Depending on the texture of the sample, 2 exhibits paramagnetic behavior or displays a very incomplete spin transition at atmospheric pressure. Complex 3 undergoes a gradual two-step spin transition with no observed hysteresis in the solid state. Both steps are approximately 100 K wide, centered at approximately 200 K and approximately 350 K, with a plateau of approximately 80 K separating the transitions. The crystal structure of 3 has been determined in steps of approximately 50 K between 400 K and 90 K, which provides a fascinating insight into the structural behavior of the complex and the nature of the spin transition. Order-disorder transitions occur in the dicyanamide bridge and the PF6(-) ions simultaneously, with the spin-crossover behavior suggesting that these transitions may trigger the two-step character. In solution, 2 and 3 display very similar continuous spin conversions. Electrochemical studies of 2 and 3 show that the voltammograms are typical of dimeric systems with electronic coupling of the metals through the dicyanamide ligand.
单核抗磁性化合物{Fe(bztpen)[N(CN)₂]}(PF₆)CH₃OH (1)（bztpen = N-苄基-N,N',N'-三(2-吡啶基甲基)乙二胺）已被合成并对其晶体结构进行了研究。配合物1可被视为两种新的双核、双氰胺桥联铁(II)配合物的形式前体，其通式为{[(Fe(bztpen)]₂[μ-N(CN)₂]}(PF₆)₃·nH₂O（n = 1 (2) 或0 (3)），已对其在固态和溶液中的性质进行了表征。在这三种配合物中，铁原子具有由bztpen配体和一个端基（1）或一个桥联双氰胺配体（2和3）定义的扭曲[FeN₆]八面体配位。在固态下，2和3可被视为分子异构体，它们因两个{Fe(bztpen)[N(CN)₂]}⁺半体的苯环相对位置不同而不同（分别为顺式和反式）。根据样品的质地，2在大气压下表现出顺磁性行为或显示出非常不完全的自旋转变。配合物3在固态下经历逐渐的两步自旋转变，未观察到滞后现象。两个步骤的宽度均约为100 K，中心分别约为200 K和约350 K，两个转变之间有一个约80 K的平台期。已在400 K至90 K之间以约50 K的步长确定了3的晶体结构，这为深入了解配合物的结构行为和自旋转变的本质提供了迷人的见解。双氰胺桥和PF₆⁻离子同时发生有序-无序转变，自旋交叉行为表明这些转变可能引发两步特征。在溶液中，2和3表现出非常相似的连续自旋转换。对2和3的电化学研究表明，伏安图是具有通过双氰胺配体进行金属电子耦合的二聚体系统的典型特征。
