Symmetry breaking in self-assembled M4L6 cage complexes
Symmetry breaking in self-assembled M4L6 cage complexes
复制标题
DOI：
10.1073/pnas.1302683110
复制
发表时间：
2013-06-25
影响因子：
11.1
通讯作者：
Nitschke, Jonathan R.
中科院分区：
文献类型：
--
作者：
Meng, Wenjing;Ronson, Tanya K.;Nitschke, Jonathan R.
在这里，我们描述了一系列 M4L6 容器分子内的对称性破缺现象。这些容器是使用基于 2,6-取代萘、蒽或蒽醌间隔基和 FeII 离子的平面刚性双齿配体合成的。配体间隔基的平面性有利于立体化学构型，其中每个笼包含两个与其他两个手性相反的金属中心，这通常会产生S-4对称的非手性构型。对称性从 S-4 减少到 C-1 是通过每个配体的结合位点对之间的空间偏移来实现的，这破坏了 S-4 对称轴。在某些情况下，使用较大的 Cd-II 或 Co-II 离子代替 Fe-II 可以观察到溶液中对称性破缺配体的动态运动。因此，这些动态配合物的 NMR 谱反映了由于能量简并的对映体 C-1 对称构象之间的快速相互转换而表现出明显的 S-4 对称性。
Here we describe the phenomenon of symmetry breaking within a series of M4L6 container molecules. These containers were synthesized using planar rigid bis-bidentate ligands based on 2,6-substituted naphthalene, anthracene, or anthraquinone spacers and FeII ions. The planarity of the ligand spacer favors a stereochemical configuration in which each cage contains two metal centers of opposite handedness to the other two, which would ordinarily result in an S-4-symmetric, achiral configuration. Reduction of symmetry from S-4 to C-1 is achieved by the spatial offset between each ligand's pair of binding sites, which breaks the S-4 symmetry axis. Using larger Cd-II or Co-II ions instead of Fe-II resulted, in some cases, in the observation of dynamic motion of the symmetry-breaking ligands in solution. NMR spectra of these dynamic complexes thus reflected apparent S-4 symmetry owing to rapid interconversion between energetically degenerate, enantiomeric C-1-symmetric conformations.