Connection of Metallamacrocycles via Dynamic Covalent Chemistry: A Versatile Method for the Synthesis of Molecular Cages

A modular approach for the synthesis of cage structures is described. Reactions of [(arene)RuCl2]2 [arene = p-cymene, 1,3,5-C6H3Me3, 1,3,5-C6H3(i-Pr)3] with formyl-substituted 3-hydroxy-2-pyridone ligands provide trinuclear metallamacrocycles with pendant aldehyde groups. Subsequent condensation reactions with di- and triamines give molecular cages with 3, 6, or 12 Ru centers in a diastereoselective and chemoselective (self-sorting) fashion. Some of the cages can also be prepared in one-pot reactions by mixing [(arene)RuCl2]2 with the pyridone ligand and the amine in the presence of base. The cages were comprehensively analyzed by X-ray crystallography. The diameter of the largest dodecanuclear complex is ∼3 nm; the cavity sizes range from 290 to 740 Å3. An amine exchange process with ethylenediamine allows the clean conversion of a dodecanuclear cage into a hexanuclear cage without disruption of the metallamacrocyclic structures.

本研究报道了一种用于笼状结构合成的模块化策略。将[(芳烃)RuCl₂]₂ [芳烃(arene) = 对伞花烃、1,3,5-三甲基苯、1,3,5-三异丙基苯]与甲酰基取代的3-羟基-2-吡啶酮配体进行反应，可得到带有悬挂醛基的三核金属大环。随后使其与二胺、三胺发生缩合反应，即可通过非对映选择性与化学选择性（自分选）的方式，得到分别含有3、6或12个钌中心的分子笼。部分分子笼还可通过一锅法制备：即在碱存在下，将[(芳烃)RuCl₂]₂、吡啶酮配体与胺类混合直接反应得到。通过X射线晶体学对所得分子笼进行了全面表征，其中最大的十二核配合物直径约为3 nm，笼腔体积介于290至740 ų之间。通过乙二胺参与的胺交换过程，可在不破坏金属大环结构的前提下，将十二核分子笼洁净转化为六核分子笼。