Laboratoire de Chimie, École Normale Supérieure de Lyon, CNRS, 46 Allée d'Italie, F-69364 Lyon, France.
J Am Chem Soc. 2010 Nov 10;132(44):15637-43. doi: 10.1021/ja104388t.
ABii diphosphonatocavitands self-assemble in chloroform solution to form dimeric molecular capsules. The molecular capsules can incarcerate an N-methylpyridinium or N-methylpicolinium guest. We have demonstrated that the supramolecular assembly acts as a molecular rotor as a result of the restricted motion of the guest inside the molecular cavity. In the solid state, X-ray diffraction analysis of the free host showed that two cavitands interact through strong hydrogen bonds to give the supramolecular self-assembled capsule. The solid-state structure of the N-methylpicolinium complex is comparable to that of the free host and indicates that the guest is not a prerequisite for the formation of the capsule. DOSY NMR studies provided a definitive argument for the formation of the free and complexed supramolecular capsule in CDCl(3) solution. In solution, the tumbling of the N-methylpyridinium and N-methylpicolinium guests about the equatorial axes of the host can be frozen and differs by the respective energy barriers, with the larger picolinium substrate having a larger value (ΔG(++) = 69.7 kJ mol(-1)) than the shorter pyridinium guest (ΔG(++) = 44.8 kJ mol(-1)). This behavior corresponds to the restricted rotation of a rotator in a supramolecular rotor.
ABii 双膦酸 Cavitands 在氯仿溶液中自组装形成二聚体分子胶囊。这些分子胶囊可以包埋 N-甲基吡啶鎓或 N-甲基吡啶鎓客体。我们已经证明，由于客体在分子腔内的受限运动，超分子组装作为分子转子起作用。在固态下，对游离主体的 X 射线衍射分析表明，两个 Cavitands 通过强氢键相互作用，形成超分子自组装胶囊。N-甲基吡啶鎓配合物的固态结构与游离主体相当，表明客体不是形成胶囊的必要条件。DOSY NMR 研究为 CDCl(3)溶液中游离和配位超分子胶囊的形成提供了明确的证据。在溶液中，客体 N-甲基吡啶鎓和 N-甲基吡啶鎓围绕主体的赤道轴的翻滚可以被冻结，并因各自的能量障碍而不同，较大的吡啶鎓底物具有较大的值（ΔG(++) = 69.7 kJ mol(-1)）比较短的吡啶客体（ΔG(++) = 44.8 kJ mol(-1)）。这种行为对应于超分子转子中旋转体的受限旋转。
