Spin crossover complexes containing 3d⁴–3d⁷ transition metal ions with tunable electronic configurations in appropriate ligand field environments have been extensively investigated. In contrast, the development of 3d⁸ divalent nickel complexes displaying such a spin crossover behavior is far behind. The increasing number of X-ray single crystal structures along with magnetic evidence and thermodynamic equilibrium indicate that bistable divalent nickel complexes are gradually recognized to be a formal member of the “spin crossover family”. Unfortunately, the rarity of nickel spin crossover complexes is occasionally mentioned. This Perspective article highlights examples of mononuclear 3d⁸ nickel spin crossover complexes in dynamic rearrangements with characterized solid state structures from the viewpoint of types of ligands utilized.

中文翻译：

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固态单核二价镍自旋交联配合物

在适当的配体场环境中，含有3d ⁴ –3d ⁷过渡金属离子且具有可调电子构型的自旋交联络合物已得到广泛研究。相反，显示出这种自旋交叉行为的3d ⁸二价镍络合物的开发却远远落后。越来越多的X射线单晶结构以及磁学证据和热力学平衡表明，双稳态二价镍络合物逐渐被认为是“自旋交联家族”的正式成员。不幸的是，偶尔会提到镍自旋交叉络合物的稀有性。本“透视”文章重点介绍了单核3d ^8的示例 从所用配体的类型来看，动态重排的镍自旋交叉络合物具有特征化的固态结构。