Bridging photochemistry and photomechanics with NMR crystallography: the molecular basis for the macroscopic expansion of an anthracene ester nanorod.
Bridging photochemistry and photomechanics with NMR crystallography: the molecular basis for the macroscopic expansion of an anthracene ester nanorod.
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具有NMR晶体学的桥接光化学和光学力学：蒽酯纳米棒宏观扩张的分子基础。
DOI：
10.1039/d0sc05118g
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发表时间：
2020-10-30
期刊：
影响因子：
8.4
通讯作者：
Mueller LJ
中科院分区：
文献类型：
--
作者：
Chalek KR;Dong X;Tong F;Kudla RA;Zhu L;Gill AD;Xu W;Yang C;Hartman JD;Magalhães A;Al-Kaysi RO;Hayward RC;Hooley RJ;Beran GJO;Bardeen CJ;Mueller LJ
由光反应分子组成的晶体代表了一类新的光机械材料，具有在快速时间尺度上产生巨大作用力的潜力。一个例子是9-叔丁基-蒽酯（9 TBAE）在分子晶体纳米棒中的光二聚化，其导致8%的平均伸长率。先前的工作表明，这种膨胀是由亚稳结晶产物的形成引起的。在这篇文章中，它显示了如何一种新的组合系综定向晶体固态NMR，X射线衍射，和第一原理计算建模可以用来建立相对于形状变化的绝对晶胞取向，揭示了原子分辨率机制的光机械响应，并使一个模型的建设，预测伸长率为7.4%，与实验值吻合良好。根据这个模型，纳米棒的膨胀不是由晶胞体积的整体变化引起的，而是由分子含量的各向异性重排引起的。定量理解分子水平光化学如何产生机械位移的能力使我们能够预测，通过控制晶胞相对于纳米棒轴的初始取向，可以将膨胀从+9%调整到-9.5%。NMR辅助结晶学的这种应用提供了一种新的工具，能够将反应分子物种的原子级结构重排与纳米结构样品的机械响应联系起来。NMR晶体学建立了相对于形状变化的绝对晶胞取向，揭示了纳米棒的光机械响应的原子分辨率机制。
Crystals composed of photoreactive molecules represent a new class of photomechanical materials with the potential to generate large forces on fast timescales. An example is the photodimerization of 9-tert-butyl-anthracene ester (9TBAE) in molecular crystal nanorods that leads to an average elongation of 8%. Previous work showed that this expansion results from the formation of a metastable crystalline product. In this article, it is shown how a novel combination of ensemble oriented-crystal solid-state NMR, X-ray diffraction, and first principles computational modeling can be used to establish the absolute unit cell orientations relative to the shape change, revealing the atomic-resolution mechanism for the photomechanical response and enabling the construction of a model that predicts an elongation of 7.4%, in good agreement with the experimental value. According to this model, the nanorod expansion does not result from an overall change in the volume of the unit cell, but rather from an anisotropic rearrangement of the molecular contents. The ability to understand quantitatively how molecular-level photochemistry generates mechanical displacements allows us to predict that the expansion could be tuned from +9% to −9.5% by controlling the initial orientation of the unit cell with respect to the nanorod axis. This application of NMR-assisted crystallography provides a new tool capable of tying the atomic-level structural rearrangement of the reacting molecular species to the mechanical response of a nanostructured sample. NMR crystallography establishes absolute unit-cell orientations relative to the shape change, revealing the atomic-resolution mechanism for the nanorod's photomechanical response.
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影响因子：
4.4
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