The research on fluorescent rotors for viscosity has attracted extensive interest to better comprehend the close relationships of microviscosity variations with related diseases. Although scientists have made great efforts, fluorescent probes for cellular viscosity with both aggregation-induced emissions (AIEs) and large Stokes shifts to improve sensing properties have rarely been reported. Herein, we first report four new meso-C═N-substituted BODIPY-based rotors with large Stokes shifts, investigate their viscosity/AIE characteristics, and perform cellular imaging of the viscosity in subcellular organelles. Interestingly, the meso-C═N-phenyl group-substituted probe 6 showed an obvious 594 nm fluorescence enhancement in glycerol and a moderate 650 nm red AIE emission in water. Further, on attaching CF₃ to the phenyl group, a similar phenomenon was observed for 7 with red-shifted emissions, attributed to the introduction of a phenyl group, which plays a key role in the red AIE emissions and large Stokes shifts. Comparatively, for phenyl-group-free probes, both the meso-C═N-trifluoroethyl group and thiazole-substituted probes (8 and 9) exhibited good viscosity-responsive properties, while no AIE was observed due to the absence of phenyl groups. For cellular experiments, 6 and 9 showed good lysosomal and mitochondrial targeting properties, respectively, and were further successfully used for imaging viscosity through the preincubation of monensin and lipopolysaccharide (LPS), indicating that C═N polar groups potentially work as rotatable moieties and organelle-targeting groups, and the targeting difference might be ascribed to increased charges of thiazole. Therefore, in this study, we investigated the structural relationships of four meso-C═N BODIPY-based rotors with respect to their viscosity/AIE characteristics, subcellular-targeting ability, and cellular imaging for viscosity, potentially serving as AIE fluorescent probes with large Stokes shifts for subcellular viscosity imaging.

中文翻译：

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用于细胞器粘度成像的新型大斯托克斯位移 Meso-C═N-BODIPY 基 AIE 荧光转子的探索

粘度荧光转子的研究引起了广泛的兴趣，以更好地理解微粘度变化与相关疾病的密切关系。尽管科学家们付出了巨大的努力，但利用聚集诱导发射（AIE）和大斯托克斯位移来提高传感性能的细胞粘度荧光探针却鲜有报道。在此，我们首先报道了四种具有大斯托克斯位移的新型内消旋-C=N-取代的基于BODIPY的转子，研究了它们的粘度/AIE特性，并对亚细胞器中的粘度进行了细胞成像。有趣的是，内消旋-C=N-苯基取代的探针6在甘油中表现出明显的594 nm荧光增强，在水中表现出中等的650 nm红色AIE发射。此外，在将CF ₃连接到苯基上时，对于具有红移发射的7观察到类似的现象，这归因于苯基的引入，这在红色AIE发射和大斯托克斯位移中起关键作用。相比之下，对于不含苯基的探针，内消旋-C=N-三氟乙基和噻唑取代的探针（8和9）均表现出良好的粘度响应特性，而由于不存在苯基而没有观察到AIE。对于细胞实验，6和9分别表现出良好的溶酶体和线粒体靶向特性，并通过莫能菌素和脂多糖（LPS）的预孵育进一步成功用于粘度成像，表明C=N极性基团有可能作为可旋转部分和细胞器-靶向组，并且靶向差异可能归因于噻唑电荷的增加。因此，在本研究中，我们研究了四种基于内消旋-C=N BODIPY的转子在粘度/AIE特性、亚细胞靶向能力和粘度细胞成像方面的结构关系，有可能作为具有大尺寸的AIE荧光探针。亚细胞粘度成像的斯托克斯位移。