Benzothiadiazole-based dibenzobenzimidazole derivatives with aggregation-induced deep-red fluorescence and different mechanically responsive fluorescence features

• Published in: Dyes and pigments 2022-09, Vol.205, p.110580, Article 110580
• Main Authors: Deng, Dian-dian, Yang, Yue, Liu, Shanting, Deng, Xiao-wen, Chen, Zhao, Pu, Shouzhi
• Format: Article
• Language: English
• Subjects: Aggregation-induced emission; Benzothiadiazole; Deep-red fluorescence; Dibenzobenzimidazole; High brightness; High-contrast mechanofluorochromism
• ISSN: 0143-7208; 1873-3743
• DOI: 10.1016/j.dyepig.2022.110580

Four novel benzothiadiazole-containing dibenzobenzimidazole derivatives were elaborately designed and successfully synthesized. Meanwhile, their molecular structures were characterized by nuclear magnetic resonance spectroscopy, mass spectrometry and elemental analysis. Interestingly, these newly synthesized dyes demonstrated remarkable aggregation-induced emission characteristics, with high brightness deep-red aggregative-state fluorescence. These highly emissive fluorophores displayed different photoluminescence in the solid state, which involved two fluorescence colors of orange and deep-red. Additionally, these fluorogenic molecules also showed different mechanically responsive emissive properties. Among them, orange emissive triad compound containing dibenzobenzimidazole, benzothiadiazole and triphenylamine units exhibited deep-red fluorescence upon treated by mechanical grinding; thus this dye possessed high-contrast mechanofluorochromism feature. In contrast, the other three deep-red fluorescent compounds showed no obvious emissive variation after grinding, indicating their negligible mechanofluorochromism phenomena. The powder X-ray diffraction experimental results provided evidence for source of the notable mechanofluorochromic behavior, and crystalline-to-amorphous morphological conversion is responsible for the observed mechanically responsive fluorescence nature. Four high brightness fluorescent dyes with remarkable aggregation-induced deep-red emission properties were developed, and solid 1 showed mechanofluorochromic behavior with high contrast beyond 90 nm. [Display omitted] •Four benzothiadiazole-modified dibenzobenzimidazole derivatives were synthesized.•All four compounds showed aggregation-induced deep-red fluorescence properties.•Fluorophores 1–4 exhibited tunable solid-state fluorescence.•Solid 1 displayed high-contrast (Δλmax ˃ 90 nm) mechanofluorochromic behavior.•Solids 2–4 displayed no visible fluorescence change in response to mechanical grinding.