Excited‐state intramolecular charge transfer (ESICT) and excited‐state intramolecular proton transfer (ESIPT) are two competitive reactions that occur in the excited states of organic dyes that contain intramolecular hydrogen‐bonds and electron acceptors and donors. Determining the mechanisms of these processes is key to understanding their multiple emission features, as the manner in which these processes interact can be modulated by modifying the dye structure. In addition, donor–π–acceptor (D–π–A) molecules often suffer from aggregation‐induced quenching. Herein, we report the synthesis of three nitrophenyl‐modified 2‐(2‐hydroxyphenyl)benzothiazole (HBT) derivatives, HBT‐s‐NO₂, HBT‐d‐NO₂, and HBT‐t‐NO₂, which have C−C, C=C, and C≡C bonds between their HBT and nitrophenyl moieties, respectively. Compared with the enol emissions from HBT‐s‐NO₂ and HBT‐t‐NO₂, that from HBT‐d‐NO₂ exhibits outstanding solvatochromism owing to consecutive ESICT‐ESIPT. In addition, X‐ray diffraction reveals that despite the highly planar and polar nature of HBT‐d‐NO₂, which is strongly H‐aggregated, it exhibits highly efficient fluorescence. Hence, this study provides new insight into the design of ESICT/ESIPT‐coupled systems and for engendering planar dipolar molecules with excellent emission properties in the solid state.

中文翻译：

---

硝基苯乙烯改性的2-（2-羟基苯基）苯并噻唑：ESICT-ESIPT的烯醇发射溶剂变色和聚集诱导的发射增强

激发态分子内电荷转移（ESICT）和激发态分子内质子转移（ESIPT）是两种竞争反应，它们发生在含有分子内氢键以及电子受体和供体的有机染料的激发态中。确定这些过程的机理是理解其多重发射特征的关键，因为可以通过修饰染料结构来调节这些过程相互作用的方式。此外，供体-π-受体（D-π-A）分子经常遭受聚集诱导的猝灭。在此，我们报告了三种硝基苯基改性的2-（2-羟基苯基）苯并噻唑（HBT）衍生物，HBT-s-NO ₂，HBT-d-NO ₂和HBT-t-NO _2的合成，它们的HBT和硝基苯基部分之间分别具有C，C = C和C≡C键。与HBT-s-NO ₂和HBT-t-NO ₂的烯醇排放相比，由于连续的ESICT-ESIPT ，HBT-d-NO ₂的烯醇排放显示出显着的溶剂变色现象。此外，X射线衍射显示，尽管HBT-d-NO ₂具有高度的H聚集性，但它具有高度的平面性和极性，但它仍显示出高效的荧光。因此，本研究为ESICT / ESIPT耦合系统的设计以及固态固态偶极分子的优异发射提供了新的见解。