Living in the salt-cocrystal continuum: indecisive organic complexes with thermochromic behaviour
Living in the salt-cocrystal continuum: indecisive organic complexes with thermochromic behaviour
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DOI：
10.1039/c8ce02066c
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发表时间：
2019-03-14
期刊：
影响因子：
3.1
通讯作者：
Thomas, Lynne H.
中科院分区：
文献类型：
--
作者：
Jones, Charlotte L.;Skelton, Jonathan M.;Thomas, Lynne H.
一个多组分卤苯胺/3,5-二硝基苯甲酸分子晶体家族具有显著的红至无色的温度诱导热致变色。发现了四对1:1中性共晶和离子盐的热致变色对，它们不同寻常地在相同条件下同时生长。发现有色共晶是亚稳的，在结晶过程中被动力学捕获，并在加热时通过质子转移转化为更稳定的盐形式。中性形式的颜色和转变的温度可以通过卤素和苯胺成分的化学取代来调节。从结构表征和第一性原理建模，我们阐明了共晶亚稳态的起源，并通过相变将结构变化与显著的可见颜色变化联系起来。通过有意利用盐-共晶连续体的不确定性，其中组分之间的小pK(a)差异可以由质子转移引起显著的固态结构重排，这项工作强调了一种新的设计范式，用于设计具有定制物理性质的新型有机热致变色材料。
A family of multicomponent haloaniline/3,5-dinitrobenzoic acid molecular crystals with striking red-to-colourless temperature-induced thermochromism is identified and characterised. Four thermochromic pairs of 1:1 neutral cocrystals and ionic salts are identified which, unusually, grow concomitantly under the same conditions. The coloured cocrystals are found to be metastable, kinetically trapped during crystallisation, and convert via proton transfer to the more stable salt forms on heating. The colour of the neutral form and the temperature of the transition can be tuned through the halogen and by chemical substitution on the aniline component. From structural characterisation and first-principles modelling, we elucidate the origin of the metastability of the cocrystals and link structural changes through the phase transition to the striking visible colour change. By deliberately exploiting the uncertainty of the salt-cocrystal continuum, where the small pK(a) difference between components enables significant solid-state structural rearrangements induced by proton transfer, this work highlights a novel design paradigm for engineering new organic thermochromics with tailored physical properties.