Samanta Shampa R, Baldridge Anthony, Tolbert Laren M, Ramamurthy Vaidhyanathan
Department of Chemistry, University of Miami, Coral Gables, Miami, Florida 33146, United States.
School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, Georgia 30332, United States.
ACS Omega. 2020 Mar 31;5(14):8230-8241. doi: 10.1021/acsomega.0c00523. eCollection 2020 Apr 14.
Cavitand octa acid (OA) is established to form a stable capsular assembly with one or two hydrophobic guest molecules (1:2 or 2:2 guest/host complex). Examples are known in which the guest molecule tumbles within the capsule without disrupting the structure of the capsuleplex. This process makes the two OA molecules that form the capsule magnetically equivalent. In this study, we have examined the dynamics of capsules that host amphiphilic benzylidene-3-methylimidazolidinone molecules as guests. In these capsuleplexes, although the guest does not tumble, the two OA molecules become magnetically equivalent because the two OA molecules that form the capsule exchange their positions in the NMR time scale. This is equivalent to the content of the capsule remaining stationary while the capsule swirls around it. Benzylidene-3-methylimidazolidinones form both 1:1 and 1:2 supramolecular complexes with cavitand OA. Two-dimensional NMR, ROESY, and NOESY data suggest that in a 300 ms time scale, the two halves of the capsule exchange between themselves and with free OA. The conclusion drawn here provides valuable information concerning the stability of the OA capsuleplex and cavitandplex that is used as the well-defined space to control the excited-state chemistry and dynamics of confined guest molecules.
穴状配体八酸（OA）已被证实可与一个或两个疏水性客体分子形成稳定的胶囊状聚集体（1:2或2:2客体/主体复合物）。已知一些例子，其中客体分子在胶囊内翻滚而不破坏胶囊复合物的结构。这个过程使得形成胶囊的两个OA分子在磁性上等价。在本研究中，我们研究了以两亲性亚苄基-3-甲基咪唑啉酮分子为客体的胶囊的动力学。在这些胶囊复合物中，尽管客体不翻滚，但两个OA分子在磁性上变得等价，因为形成胶囊的两个OA分子在核磁共振时间尺度上交换了它们的位置。这相当于胶囊围绕其内容物旋转时内容物保持静止。亚苄基-3-甲基咪唑啉酮与穴状配体OA形成1:1和1:2的超分子复合物。二维核磁共振、旋转坐标系中的核欧沃豪斯效应（ROESY）和核欧沃豪斯效应（NOESY）数据表明，在300毫秒的时间尺度内，胶囊的两半之间以及与游离OA之间会相互交换。这里得出的结论为OA胶囊复合物和穴状配体复合物的稳定性提供了有价值的信息，这些复合物被用作控制受限客体分子激发态化学和动力学的明确空间。
