Restricted Guest Tumbling in Phosphorylated Self-Assembled Capsules

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• 作者：Steven Harthong ; Batrice Dubessy ; Jrme Vachon ; Christophe Aronica ; Jean-Christophe Mulatier ; Jean-Pierre Dutasta
• 刊名：Journal of the American Chemical Society
• 出版年：2010
• 出版时间：November 10, 2010
• 年：2010
• 卷：132
• 期：44
• 页码：15637-15643
• 全文大小：384K
• 年卷期：v.132,no.44(November 10, 2010)
• ISSN：1520-5126

文摘

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 CDCl₃ 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.