Structures and Chromogenic Properties of Bisimidazole Derivatives

Two imidazole derivatives, 2,2‘-(2,5-thiophenediyl)bis[4,5-diphenyl-1H-imidazole] (1) and 2,2‘-(1,4-phenylene)bis[4,5-diphenyl-1H-imidazole] (3), were synthesized and crystallized from different solvents. The crystal solvates have different colors,
and some of these compounds show piezochromism, photochromism, and thermochromism in the solid state and show solvatochromism,
halochromism, and photochromism in solution. The X-ray crystal structures of bisimidazole derivatives of lophine and the spectroscopic
properties and photochemistry of these compounds in solutions are reported. The thermal behavior of the crystalline compounds
was studied by a calorimetric method, and it was shown that upon heating the crystal solvates lose the solvent molecules, and the
color is changed to the original color of the nonsolvate parent compound. The conclusion is that hydrogen bonding is responsible
for the different colors.

本研究合成了两种咪唑衍生物（imidazole derivatives），分别为2,2'-(2,5-噻吩二基)双[4,5-二苯基-1H-咪唑]（1）与2,2'-(1,4-亚苯基)双[4,5-二苯基-1H-咪唑]（3），并通过不同溶剂完成结晶。该系列化合物的溶剂化晶体呈现出各异的色泽；部分化合物在固态下可表现出压致变色（piezochromism）、光致变色（photochromism）与热致变色（thermochromism），在溶液中则展现出溶剂致变色（solvatochromism）、卤致变色（halochromism）与光致变色特性。本文报道了洛非辛（lophine）类双咪唑衍生物的X射线晶体结构，以及此类化合物在溶液中的光谱性质与光化学行为。本研究通过量热法对结晶态化合物的热行为进行了考察，结果显示，加热溶剂化晶体时，其会脱除溶剂分子，颜色随之转变为非溶剂化母体化合物的原始色泽。最终研究结论表明，氢键是造成颜色差异的关键因素。