We describe here a family of coordination cages with interesting structural, guest-binding, and catalytic properties. Flexible bridging ligands containing two bidentate pyrazolylpyridine termini assemble with transition-metal dications to afford coordination cages containing a metal ion at each vertex, a bridging ligand spanning each edge, and a 2:3 metal:ligand ratio. This stoichiometry is expressed in structures ranging from M₄L₆ tetrahedra to M₁₆L₂₄ tetracapped truncated tetrahedra, which are stabilized by the formation of π-stacked arrays between electron-rich and electron-poor ligand segments that form around the cage periphery. In some cases concentration- and/or temperature-dependent equilibria between multiple cage structures occur, arising from a balance between entropy, which favors the formation of a larger number of smaller assemblies, and enthalpy, which maximizes both interligand aromatic stacking and solvophobic effects in the larger assembles.

中文翻译：

---

基于双（吡唑基吡啶）配体的配位笼：结构，动态行为，来宾绑定和催化。

我们在这里描述了一个具有有趣的结构，客体结合和催化特性的配位笼系列。包含两个双齿吡唑基吡啶末端的柔性桥连配体与过渡金属指示剂组装在一起，形成配位笼，每个顶点上都包含金属离子，跨过每个边缘的桥连配体，以及金属与配体的比例为2：3。这种化学计量以从M ₄ L ₆四面体到M ₁₆ L _24的结构表示四盖的截短的四面体，通过在笼周围形成的富电子和贫电子配体链段之间形成π堆叠阵列而稳定。在某些情况下，由于笼罩之间的平衡而引起的多个笼形结构之间的浓度和/或温度相关的平衡，这有利于形成大量较小的组件，而焓则使配位体芳族堆积和疏油效应最大化。较大的组件。