A fluorescent rotary dye (DPTPA4) based on dipyridylphenylamine was designed and synthesized, of which all phenyl and pyridinium rings were conjugated through the twisted single bonds. Because of the free rotary framework, DPTPA4 shows short emission from 406 nm to 470 nm in organic solvents with different polarity assigned to the weak charge transfer located on the triphenylamine moiety. On the other hand, DPTPA4 can output the longer emission in near-infrared region (650–670 nm) in both glycerol aqueous and BSA-containing buffers from the restriction of molecular rotation from the viscosity and hydrophobic circumstance. The fluorescence decay experiments evidence both circumstances can stabilize the excitated state of DPTPA4 in which the longer lifetime was obtained (0.95 ns in glycerol and 1.84 ns with BSA). Furthermore, the cell imaging test of DPTPA4 indicated our probe could target the specific region near the nuclei. This work proves the design of near-infrared enhanced emission platform based on restriction of molecular rotation and provides a candidate for light-up the specific sites at subcellular levels.

设计并合成了基于二吡啶基苯基胺的荧光旋转染料（DPTPA4），其中所有的苯基和吡啶鎓环均通过扭曲的单键共轭。由于具有自由的旋转骨架，DPTPA4在有机溶剂中显示出从406 nm到470 nm的短发射，极性不同的有机溶剂分配给位于三苯胺部分的弱电荷转移。另一方面，DPTPA4可以在甘油水性缓冲液和含BSA的缓冲液中在近红外区域（650-670 nm）输出更长的发射光，这是由于分子旋转受粘度和疏水性的限制。荧光衰减实验证明两种情况都能稳定DPTPA4的激发态其中获得了更长的使用寿命（甘油中为0.95 ns，BSA中为1.84 ns）。此外，DPTPA4的细胞成像测试表明我们的探针可以靶向细胞核附近的特定区域。这项工作证明了基于分子旋转限制的近红外增强发射平台的设计，并为在亚细胞水平上点亮特定位点提供了候选。