Synthetic macrocycles have proved to be of great application value in functional charge-transfer systems in the solid state in recent years. Here we show a switchable on-off type vapochromic system toward 1-/2-bromoalkane isomers by constructing solid-state charge-transfer complexes between electron-rich perethylated pillar[5]arene and electron-deficient aromatic acceptors including 4-nitrobenzonitrile and 1,4-dinitrobenzene. These charge-transfer complexes with different colors show opposite color changes upon exposure to the vapors of 1-bromoalkanes (fading) and 2-bromoalkanes (deepening). Single-crystal structures incorporating X-ray powder diffraction and spectral analyses demonstrate that this on-off type vapochromic behavior is mainly attributed to the destruction (off) and reconstruction (on) of the charge-transfer interactions between perethylated pillar[5]arene and the acceptors, for which the competitive host-guest binding of 1-bromoalkanes and the solid-state structural transformation triggered by 2-bromoalkanes are respectively responsible. This work provides a simple colorimetric method for distinguishing positional isomers with similar physical and chemical properties.

近年来，合成大环化合物已被证明在固态功能电荷转移系统中具有巨大的应用价值。在这里，我们通过在富电子的全乙基化柱[5]芳烃和缺电子芳香族受体（包括4-硝基苯甲腈和1）之间构建固态电荷转移络合物，展示了一种针对1-/2-溴烷异构体的可开关型气致变色系统。 ,4-二硝基苯。这些具有不同颜色的电荷转移络合物在暴露于 1-溴烷烃（褪色）和 2-溴烷烃（加深）蒸气时表现出相反的颜色变化。结合X射线粉末衍射和光谱分析的单晶结构表明，这种开关型气色行为主要归因于全乙基化柱[5]芳烃和受体，分别负责1-溴烷烃的竞争性主客体结合和2-溴烷烃引发的固态结构转变。这项工作为区分具有相似物理和化学性质的位置异构体提供了一种简单的比色方法。