Organic materials possessing solid-state emission responsive to external stimuli have significance in a variety of material, biomedical, and optoelectronic applications. Organic molecules having different donor–acceptor architectures integrated with aggregation-induced emission (AIE) fluorophores have been utilized in development of mechanofluorochromic (MFC) materials. In this work, we have designed and synthesized phenanthroimidazole (PI) based derivatives TPE-PI-1, TPE-PI-2, TPE-PI-3, PTZ-PI-1, PTZ-PI-2, and PTZ-PI-3 where in donors tetraphenylethylene-TPE (D) and phenothiazine-PTZ (D′) of contrasting donor abilities are attached to the N and C atom positions of PI. The position and mode of attachment of the donors have been changed, and an additional PTZ spacer has been introduced which has a direct consequence on their photophysical and electronic properties. The PI derivatives manifest AIE, solvatochromic, and mechanochromic behavior. The single crystal X-ray analysis of TPE-PI-1 and PTZ-PI-2 reveals bent structures for the PTZ unit and a twisted conformation for TPE moieties. The density functional theory calculations were used to obtain optimized ground-state structures of the PI derivatives. The work shows a comprehensive comparison of the photophysical, electronic, AIE, and MFC properties of the PI derivatives as an effect of variations in the position of donor, donor–acceptor strength, and change in molecular conformation on use of spacer.

中文翻译：

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苯并咪唑衍生物的机械变色和聚集诱导的发射：多发色组装中不同供体位置变化的作用

具有对外部刺激响应的固态发射的有机材料在各种材料，生物医学和光电应用中具有重要意义。具有不同供体-受体结构的有机分子与聚集诱导发射（AIE）荧光团集成在一起，已被用于开发机械荧光致变色（MFC）材料。在这项工作中，我们设计并合成了基于菲并咪唑（PI）的衍生物TPE-PI-1，TPE-PI-2，TPE-PI-3，PTZ-PI-1，PTZ-PI-2和PTZ-PI- 3其中供体能力相反的四苯基乙烯-TPE（D）和吩噻嗪-PTZ（D'）连接到PI的N和C原子位置。供体的位置和连接方式已更改，并引入了一个附加的PTZ间隔物，这直接影响了它们的光物理和电子性能。PI衍生物表现出AIE，溶剂变色和机械变色行为。TPE-PI-1和PTZ-PI-2的单晶X射线分析揭示了PTZ单元的弯曲结构和TPE部分的扭曲构象。密度泛函理论计算用于获得PI衍生物的优化基态结构。这项工作显示了PI衍生物的光物理，电子，AIE和MFC特性的全面比较，这些特性是对供体位置变化，供体-受体强度以及间隔基使用中分子构象变化的影响。