Piezochromism and hydrochromism through electron transfer: new stories for viologen materials.
Piezochromism and hydrochromism through electron transfer: new stories for viologen materials.
复制标题
通过电子转移实现压致变色和水致变色：紫精材料的新故事
DOI：
10.1039/c6sc04579k
复制
发表时间：
2017-04-01
期刊：
影响因子：
8.4
通讯作者：
Wang L
中科院分区：
文献类型：
--
作者：
Sui Q;Ren XT;Dai YX;Wang K;Li WT;Gong T;Fang JJ;Zou B;Gao EQ;Wang L
吡啶鎓-羧酸盐化合物在压力下由于通过电子转移形成自由基而发生可逆的颜色变化;脱水和水合也可以引发电子转移。虽然紫精衍生物早已被称为电致变色和光致变色，在这里，我们证明了紫精羧酸盐两性离子分子在结晶状态下表现出压致变色和水致变色行为。黄色晶体经历可逆的颜色变化，在高压下变为红色，在减压后变为绿色，最后在环境压力下静置时变回黄色。紫外-可见光谱、X射线光电子能谱、电子顺磁共振X射线衍射和密度泛函理论计算表明，这种压色性是由于羧酸盐与吡啶盐之间通过压力诱导电子转移形成自由基而引起的，没有晶体学相变。有人提出，电子转移诱导的压力强迫还原的分子间的供体-受体接触。电子转移也可以通过脱水来诱导，这给出了稳定的绿色无水自由基相。颜色变化在水的重吸收后是可逆的，这触发了反向电子转移。该化合物不仅展示了紫精化合物的新变色现象，而且代表了与通过电子转移形成自由基相关的有机机械变色和水致变色的第一个例子。
A pyridinium-carboxylate compound undergoes reversible color change under pressure owing to the formation of radicals via electron transfer; dehydration and hydration can also trigger electron transfer. While viologen derivatives have long been known for electrochromism and photochromism, here we demonstrated that a viologen-carboxylate zwitterionic molecule in the crystalline state exhibits piezochromic and hydrochromic behaviors. The yellow crystal undergoes a reversible color change to red under high pressure, to green after decompression, and finally back to yellow upon standing at ambient pressure. Ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance X-ray diffraction and DFT calculations suggested that the piezochromism is due to the formation of radicals via pressure-induced electron transfer from carboxylate to pyridinium, without a crystallographic phase transition. It was proposed that electron transfer is induced by pressure-forced reduction of intermolecular donor–acceptor contacts. The electron transfer can also be induced by dehydration, which gives a stable green anhydrous radical phase. The color change is reversible upon reabsorption of water, which triggers reverse electron transfer. The compound not only demonstrates new chromic phenomena for viologen compounds, but also represents the first example of organic mechanochromism and hydrochromism associated with radical formation via electron transfer.