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：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），并分别通过不同溶剂完成结晶。该类化合物的溶剂化物晶体呈现出各异的色泽；其中部分目标化合物在固态下可表现出压致变色、光致变色及热致变色行为，在溶液中则展现出溶剂致变色、卤致变色与光致变色特性。本文报道了洛菲碱（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。研究团队采用量热法对结晶态样品的热性能进行了探究，结果显示：对溶剂化物晶体进行加热时，其会释放溶剂分子，颜色随之转变为非溶剂化母体化合物的原始色泽。最终结论为：氢键是导致上述颜色差异的核心因素。