Experimental and computational probes of the space in a self-assembled capsule
Experimental and computational probes of the space in a self-assembled capsule
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DOI：
10.1073/pnas.0602781103
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发表时间：
2006-06-13
影响因子：
11.1
通讯作者：
Rebek, Julius, Jr.
中科院分区：
文献类型：
--
作者：
Ajami, Dariush;Iwasawa, Tetsuo;Rebek, Julius, Jr.
自组装胶囊是识别并包围适当大小、形状和化学表面的小分子客体的宿主。内部可用的空间是固定溶剂分子的笼子，其中许多是芳香族的。这些芳烃提供各向异性屏蔽的客人，和内部空间的感应磁屏蔽的地图可以通过核独立的化学位移计算。磁环境的实验值可以通过内部客体的NMR谱来确定。我们在这里描述的环境中的一个圆柱形胶囊与锥形的结束。合成了一系列末端乙炔--有机结构的最外层--并用来探测胶囊末端的磁屏蔽。他们的核磁共振谱显示，当炔属氢被迫深入到四个苯环会聚的胶囊的锥形末端时，炔属氢经历了去屏蔽。建模和密度泛函理论计算提供了极好的协议与实验值，并建立了一个分子标尺，探索胶囊内的空间和磁环境。
Self-assembled capsules are hosts that recognize and surround smaller molecule guests of appropriate size, shape, and chemical surfaces. The space available inside is a cage of fixed solvent molecules, many of which are aromatic. These aromatics provide anisotropic shielding to guests, and a map of induced magnetic shielding for the inner space can be obtained through nucleus-independent chemical shift calculations. Experimental values of the magnetic environment can be determined by NMR spectra of the guests inside. We describe here the environment in a cylindrical capsule with tapered ends. A series of terminal acetylenes-the narrowest of organic structures-was synthesized and used to probe the magnetic shielding of the capsule's ends. Their NMR spectra showed that the acetylenic hydrogen experiences deshielding as it is forced deeper into the tapered end of the capsule where four benzene rings converge. Modeling and density functional theory calculations provided excellent agreement with the experimental values and established a molecular ruler to explore steric and magnetic environments inside the capsule.