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首页> 美国卫生研究院文献>other >Amphidynamic Crystals of a Steroidal Bicyclo2.2.2octane Rotor: A High Symmetry Group that Rotates Faster than Smaller Methyl and Methoxy Groups
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Amphidynamic Crystals of a Steroidal Bicyclo2.2.2octane Rotor: A High Symmetry Group that Rotates Faster than Smaller Methyl and Methoxy Groups

机译：甾族双环2.2.2辛烷转子的两性动力学晶体：高对称性组其旋转速度快于较小的甲基和甲氧基基团

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摘要

The synthesis, crystallization, single crystal X-ray structure, and solid state dynamics of molecular rotor >3 provided with a high symmetry order and relatively cylindrical bicyclo[2.2.2]octane (BCO) rotator linked to mestranol fragments were investigated in this work. Using solid state 13C NMR, three rotating fragments were identified within the molecule: the BCO, the C19 methoxy and the C18 methyl groups. To determine the dynamics of the BCO group in crystals of >3 by variable temperature 1H spin-lattice relaxation (VT 1H–T1), we determined the 1H–T1 contributions from the methoxy group C19 by carrying out measurements with the methoxy-deuterated isotopologue rotor >3-d6. The contributions from the quaternary methyl group C18 were estimated by considering the differences between the VT 1H–T1 of mestranol >8 and methoxy-deuterated mestranol >8-d3. From these studies it was determined that the BCO rotator in >3 has an activation energy of only 1.15 kcal mol−1, with a barrier for site exchange that is smaller than those of methyl (Ea = 1.35 kcal mol−1) and methoxy groups (Ea = 1.91 kcal mol−1), despite their smaller moments of inertia and surface areas.
机译：分子转子> 3 的合成，结晶，单晶X射线结构和固态动力学，具有对称性高的顺序，并且与麦甾醇连接的相对圆柱形的双环[2.2.2]辛烷（BCO）转子碎片在这项工作中进行了调查。使用固态13 C NMR，在分子内鉴定出三个旋转片段：BCO，C19甲氧基和C18甲基。要通过可变温度 1 H自旋晶格弛豫（VT 1 H–T1）确定> 3 晶体中BCO基团的动力学，我们通过用甲氧基氘代同位素异构体转子> 3 -d6进行测量，确定了甲氧基C19的 1 H–T1贡献。考虑到甲基雌醇> 8 的VT 1 H–T1与甲氧基氘代甲基雌醇> 8 之间的差异，估算了甲基C18的贡献> -d3。从这些研究中可以确定，> 3 中的BCO旋转器的活化能仅为1.15 kcal mol -1 ，且位点交换的障碍小于甲基（Ea = 1.35 kcal mol -1 ）和甲氧基（Ea = 1.91 kcal mol -1 ），尽管它们的惯性矩和表面积较小。

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