Cracking under Internal Pressure: Photodynamic Behavior of Vinyl Azide Crystals through N 2 Release
Cracking under Internal Pressure: Photodynamic Behavior of Vinyl Azide Crystals through N 2 Release
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内压下的裂解：乙烯基叠氮化物晶体通过 N 2 释放的光动力行为
DOI：
10.1021/jacs.0c07830
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发表时间：
2020
影响因子：
15
通讯作者：
Naumov, Panče
中科院分区：
文献类型：
--
作者：
Shields, Dylan J.;Karothu, Durga Prasad;Sambath, Karthik;Ranaweera, Ranaweera A.;Schramm, Stefan;Duncan, Alexander;Duncan, Benjamin;Krause, Jeanette A.;Gudmundsdottir, Anna D.;Naumov, Panče
当暴露于UV光时，乙烯基叠氮化合物3-叠氮基-1-苯基丙烯酮（1a）、3-叠氮基-1-（4-甲氧基苯基）丙烯酮（1b）和3-叠氮基-1-（4-氯苯基）丙烯酮（1c）的单晶通过破裂或弯曲并释放N2而表现出显著的机械效应。使用激光闪光光解的机制研究，量子力学计算的支持下，表明每个乙烯基叠氮化物通过乙烯基氮烯中间体降解。然而，尽管具有非常相似的晶体包装图案，这三种化合物在大块晶体中表现出不同的光机械响应。在石蜡油中，1带1 c的晶体分层并无差别地释放气态N2，而1带1 c的晶体在释放N2之前明显地膨胀、弯曲和断裂，主要是沿沿着特定的晶面。光化学分析表明，所观察到的膨胀是由于这些材料的晶格中的气体产物所施加的内部压力。晶格能计算，纳米压痕实验的支持下，显示各自的晶格能显着差异。计算确定的关键功能，在晶体结构的1band 1c的弹性能量积累在气体释放过程中，这对应于所观察到的裂纹的方向。这项研究突出了迄今尚未开发的潜力，光化学气体释放引起的光机械响应和运动的光反应分子晶体。
When exposed to UV light, single crystals of the vinyl azides 3-azido-1-phenylpropenone (1a), 3-azido-1-(4-methoxyphenyl)propenone (1b), and 3-azido-1-(4-chlorophenyl)propenone (1c) exhibit dramatic mechanical effects by cracking or bending with the release of N2. Mechanistic studies using laser flash photolysis, supported by quantum mechanical calculations, show that each of the vinyl azides degrades through a vinylnitrene intermediate. However, despite having very similar crystal packing motifs, the three compounds exhibit distinct photomechanical responses in bulk crystals. While the crystals of1adelaminate and release gaseous N2indiscriminately under paraffin oil, the crystals of1band1cvisibly expand, bend, and fracture, mainly along specific crystallographic faces, before releasing N2. The photochemical analysis suggests that the observed expansion is due to internal pressure exerted by the gaseous product in the crystal lattices of these materials. Lattice energy calculations, supported by nanoindentation experiments, show significant differences in the respective lattice energies. The calculations identify critical features in the crystal structures of1band1cwhere elastic energy accumulates during gas release, which correspond to the direction of the observed cracks. This study highlights the hitherto untapped potential of photochemical gas release to elicit a photomechanical response and motility of photoreactive molecular crystals.