The Roles of Intrinsic Barriers and Crystal Fluidity in Determining the Dynamics of Crystalline Molecular Rotors and Molecular Machines
The Roles of Intrinsic Barriers and Crystal Fluidity in Determining the Dynamics of Crystalline Molecular Rotors and Molecular Machines
复制标题
DOI：
10.1021/acs.joc.9b00993
复制
发表时间：
2019-08-16
影响因子：
3.6
通讯作者：
Garcia-Garibay, Miguel A.
中科院分区：
文献类型：
--
作者：
Howe, Morgan E.;Garcia-Garibay, Miguel A.
晶体固体是分子机器发展的一个有前途的平台。它们有可能将异构化、构象运动或化学反应引起的物理性质的分子水平控制与长程有序和多尺度现象引起的涌现性质相结合。然而，由于能够支持固态高阶和受控分子运动的结构设计存在困难，因此晶体分子机械的构建一直具有挑战性，我们将固态平台称为两动晶体。以超快旋转为目标，以前对两动晶体的研究已经探索了旋转体周围自由空间的产生，体积守恒旋转运动的优点，以及与相关旋转或齿轮运动相关的挑战。在这一观点中，我们报告了对我们和其他人的工作中的大量例子进行系统分析的结果，在这些例子中，我们证明了自由空间的创造并不总是导致超快动力学。在适用于具有大空体积的多孔晶体（例如MOFs和其他扩展固体）的限制中，内部运动落入激活控制的范围内，其中动力学由用于围绕连接转子和定子的键旋转的固有（气相）电子势垒确定。相比之下，内旋转紧密堆积的分子晶体福尔斯的政权的扩散控制的动力学，并依赖于旋转器周围的扭曲和创建瞬态腔的能力。我们把这种性质称为“晶体流动性”，并建议它可以作为设计晶体分子机器的额外指导原则。我们在这里描述的晶体分子机械的前景领域背后的一般原则，分析方法来分析晶体固体的旋转动力学，和关键的结构概念，可能有助于他们的未来发展。
Crystalline solids are a promising platform for the development of molecular machines. They have the potential of combining the molecular-level control of physical properties caused by isomerizations, conformational motions, or chemical reactions with the emergent properties that arise from long-range order and multiscale phenomena. However, the construction of crystalline molecular machinery has been challenging due to the difficulties associated with the design of structures capable of supporting high order and controlled molecular motion in the solid state, a platform that we term amphidynamic crystals. With ultrafast rotation as the target, previous work on amphidynamic crystals has explored the creation of free space around the rotator, the advantages of volume-conserving rotational motions, and the challenges associated with correlated rotations, or gearing motions. In this Perspective we report the results of a systematic analysis of a large number of examples from our work and that of others, where we demonstrate that the creation of free space alone does not always result in ultrafast dynamics. In a limit that applies to porous crystals with large empty volumes such as MOFs and other extended solids, internal motions fall in the regime of activation control, with dynamics determined by the intrinsic (gas-phase) electronic barriers for rotation around the bond that connects the rotator and the stator. By contrast, internal rotation in close-packed molecular crystals falls in the regime of diffusion-controlled dynamics and depends on the ability of the rotator surroundings to distort and create transient cavities. We refer to this property as "crystal fluidity" and suggest that it may be used as an additional guiding principle for the design of crystalline molecular machines. We describe here the general principles behind the promising field of crystalline molecular machinery, the analytical methods to analyze rotational dynamics of crystalline solids, and the key structural concepts that may help their future development.