A family of Pd₂L₄ cages prepared from ligands based on an axially chiral diamino-[1,1′-biazulene] motif (serving as a unique azulene-based surrogate of the ubiquitous BINOL moiety) is reported. We show that preparing a cage starting from the racemate of a shorter bis-monodentate ligand derivative, equipped with pyridine donor groups, leads to integrative (“social”) chiral self-sorting, exclusively yielding the meso-trans product, but only in a selection of solvents. This phenomenon is driven by individual solvent molecules acting as hydrogen bonding tethers between the amino groups of neighboring ligands, thereby locking the final coordination cage in a single isomeric form. The experimental (solvent-dependent NMR, single-crystal X-ray diffraction) observations of this cooperative interaction could be explained by computational analyses only when explicit solvation was considered. Furthermore, we prepared a larger chiral ligand with isoquinoline donors, which, unlike the first one, does not undergo social self-sorting from its racemic mixture, further highlighting the importance of solvents bridging short distances between the amino groups. Homochiral cages formed from this larger ligand, however, furnish a cavity that can bind anionic and neutral metal complexes such as [Pt(CN)₆]^2– and Cr(CO)₆ and discriminate between the two enantiomers of chiral guest camphor sulfonate.

中文翻译：

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Pd2L4 配位笼中的溶剂导向社会手性自分选


据报道，由基于轴向手性二氨基-[1,1′-biazulene] 基序的配体制备的 Pd₂L₄ 笼家族（作为普遍存在的 BINOL 部分的独特基于蓝氮的替代物）。我们表明，从较短的双单齿配体衍生物的外消旋体开始制备笼子，配备吡啶供体基团，导致整合（“社会”）手性自分选，仅产生内消旋反产物，但仅在选择溶剂中。这种现象是由单个溶剂分子驱动的，这些溶剂分子充当相邻配体的氨基之间的氢键系绳，从而将最终的配位笼锁定在单个异构体形式中。只有当考虑显式溶剂化时，这种协同相互作用的实验（溶剂依赖性 NMR、单晶 X 射线衍射）观察才能通过计算分析来解释。此外，我们制备了一种具有异喹啉供体的更大的手性配体，与第一种不同，它不会从其外消旋混合物中进行社会性自分选，进一步强调了溶剂桥接氨基之间短距离的重要性。然而，由这种较大的配体形成的同手性笼提供了一个空腔，该空腔可以结合阴离子和中性金属络合物，如 [Pt（CN）₆]^2– 和 Cr（CO）₆，并区分手性客体樟脑磺酸盐的两种对映异构体。