Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, CNRS UMR 8601, PRES Sorbonne Paris Cité, Université Paris Descartes, 45 rue des Saints Pères, 75006 Paris, France.
Inorg Chem. 2013 Apr 15;52(8):4683-91. doi: 10.1021/ic4002863. Epub 2013 Apr 3.
Two new polytopic ligands based on a calix[6]arene scaffold were synthesized. The truncated cone-shaped calixarene was functionalized at its small rim by a tris-imidazole site, aimed at generating a tetrahedral Zn(II) complex, where a fourth labile site inside the cavity is accessible through the funnel provided by its large rim. Tridentate aza ligands (either two or three) were then grafted at this large rim (the entrance of the cavity). Zn(II) coordination studies, monitored by (1)H NMR spectroscopy, showed unprecedented behavior in this family of heteropolytopic ligands. Indeed, it gives access to complexes of various nuclearities in acetonitrile, where zinc binding is under the supramolecular control of the guest. It is first shown that, in the absence of a good guest donor (a primary amine), Zn(II) binding is favored at the large rim where two tridentate nitrogenous groups can form an octahedral complex. The addition of a long guest such as heptylamine induces the quantitative translocation of the Zn(II) ion from the large rim octahedral (O(h)) site to the small rim tetrahedral (T(d)) site provided by the trisimidazole core and the guest ligand. With 2 equiv of Zn(II), well-defined dinuclear complexes were obtained and isolated, with one Zn(II) ion bound at each rim. Interestingly, it is shown that the binding mode at the large rim is under the supramolecular control of the guest bound at the small rim (with short guests, the O(h) environment is obtained at the large rim, whereas long guests disrupt this core through an induced-fit process); the partially included and dangling alkyl chain opens the large rim (entrance of the cavity) and pushes apart the tridentate moieties. As a result, a guest-induced switch of Zn(II) binding mode occurs and frees one of the tridentate groups from coordination, allowing further extension of the complex nuclearity.
合成了两种基于杯[6]芳烃骨架的新的多齿配体。截顶锥形杯芳烃在其小边缘处通过三咪唑位点功能化，旨在生成四面体 Zn(II) 配合物，其中空腔内部的第四个不稳定位点可通过其大边缘提供的漏斗进入。然后在该大边缘（空腔的入口）上接枝三齿氮配体（两个或三个）。Zn(II) 配位研究，通过（1）H NMR 光谱监测，在这种杂多齿配体家族中表现出前所未有的行为。事实上，它可以在乙腈中获得各种核的配合物，其中锌的结合受客体的超分子控制。首先表明，在没有良好的客体供体（伯胺）的情况下，Zn(II) 结合更倾向于大边缘，在那里两个三齿氮基团可以形成八面体配合物。添加长客体如庚胺会诱导 Zn(II) 离子从大边缘八面体（O(h)）位定量迁移到由三咪唑核和客体配体提供的小边缘四面体位（T(d)）。用 2 当量的 Zn(II)，得到并分离出了定义明确的双核配合物，每个边缘各有一个 Zn(II) 离子结合。有趣的是，表明大边缘的结合模式受小边缘结合的客体的超分子控制（对于短客体，在大边缘获得 O(h) 环境，而长客体通过诱导适合过程破坏该核；部分包含和悬垂的烷基链打开大边缘（空腔入口）并将三齿部分推开。结果，发生了 Zn(II) 结合模式的客体诱导开关，使一个三齿基团从配位中释放出来，允许进一步扩展配合物的核性。
