Ultrafast rotation in an amphidynamic crystalline metal organic framework
Ultrafast rotation in an amphidynamic crystalline metal organic framework
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DOI：
10.1073/pnas.1708817115
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发表时间：
2017-12-26
影响因子：
11.1
通讯作者：
Garcia-Garibay, Miguel A.
中科院分区：
文献类型：
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作者：
Vogelsberg, Cortnie S.;Uribe-Romo, Fernando J.;Garcia-Garibay, Miguel A.
双动力晶体是一种新兴的凝聚态物质，由晶格形成元素的组合设计而成，这些元素与在固态中显示工程动力学的组件相连接。在这里，我们设计了一种在纳米尺度上具有惯性扩散旋转的分子转子晶体阵列，其特征是没有位阻或电子势垒。我们用1,4-双环[2.2.2]辛烷二羧酸（BODCA）MOF解决了这一挑战，这是一种在zn40立方晶格中由高对称双环[2.2.2]辛烷二羧酸连接剂构建的金属有机框架（MOF）。在2.3 ~ 80 K的温度范围内，利用29.49和13.87 MHz的自旋-晶格弛豫H-1固体核磁共振，我们发现在能垒为0.185 kcal mol（-1）的势中发生了内旋。这些结果与H-2固体核磁共振线形分析和在6 ~ 298 K范围内获得的76.78 MHz的自旋晶格弛豫相一致，并结合分子动力学模拟表明，惯性扩散旋转具有广泛的角位移范围，在任何给定位置都没有停留时间。BODCA-MOF中双环[2.2.2]辛烷（BCO）基团的室温旋转构成了一个例子，在固体状态下的工程旋转动力学与它们在高密度气体或低密度液相中的旋转动力学一样快。
Amphidynamic crystals are an emergent class of condensed phase matter designed with a combination of lattice-forming elements linked to components that display engineered dynamics in the solid state. Here, we address the design of a crystalline array of molecular rotors with inertial diffusional rotation at the nanoscale, characterized by the absence of steric or electronic barriers. We solved this challenge with 1,4-bicyclo[2.2.2] octane dicarboxylic acid (BODCA)MOF, a metal-organic framework (MOF) built with a high-symmetry bicyclo[2.2.2] octane dicarboxylate linker in a Zn4O cubic lattice. Using spin-lattice relaxation H-1 solid-state NMR at 29.49 and 13.87 MHz in the temperature range of 2.3-80 K, we showed that internal rotation occurs in a potential with energy barriers of 0.185 kcal mol(-1). These results were confirmed with H-2 solid-state NMR line-shape analysis and spin-lattice relaxation at 76.78 MHz obtained between 6 and 298 K, which, combined with molecular dynamics simulations, indicate that inertial diffusional rotation is characterized by a broad range of angular displacements with no residence time at any given site. The ambient temperature rotation of the bicyclo[2.2.2] octane (BCO) group in BODCA-MOF constitutes an example where engineered rotational dynamics in the solid state are as fast as they would be in a high-density gas or in a low-density liquid phase.