Department of Organic Synthesis, University of Chemical Technology and Metallurgy, 8 Kliment Ohridsky Str., 1756 Sofia, Bulgaria.
Bulgarian Academy of Sciences, 1040 Sofia, Bulgaria.
Molecules. 2022 Nov 4;27(21):7556. doi: 10.3390/molecules27217556.
A novel highly water-soluble 1,8-naphthalimide with pH and viscosity-sensing fluorescence was synthesized and investigated. The synthesized compound was designed as a molecular device in which a molecular rotor and molecular "off-on" switcher were integrated. In order to obtain a TICT driven molecular motion at C-4 position of the 1,8-naphthalimide fluorophore, a 4-methylpiperazinyl fragment was introduced. The molecular motion was confirmed after photophysical investigation in solvents with different viscosity; furthermore, the fluorescence-sensing properties of the examined compound were investigated in 100% aqueous medium and it was found that it could be used as an efficient fluorescent probe for pH. Due to the non-emissive deexcitation nature of the TICT fluorophore, the novel system showed low yellow-green emission, which represented "power-on"/"rotor-on" state. The protonation of the methylpiperazine amine destabilized the TICT process, which was accompanied by fluorescence enhancement indicating a "power-on"/"rotor-off" state of the system. The results obtained clearly illustrated the great potential of the synthesized compound to serve as pH- and viscosity-sensing material in aqueous solution.
合成并研究了一种新型的高水溶性 1,8-萘酰亚胺，具有 pH 值和粘度感应荧光。合成的化合物被设计为一种分子器件，其中集成了分子转子和分子“开-关”开关器。为了在 1,8-萘酰亚胺荧光团的 C-4 位置获得 TICT 驱动的分子运动，引入了 4-甲基哌嗪基片段。在不同粘度的溶剂中进行光物理研究后，确认了分子运动；此外，还在 100%水介质中研究了所检查化合物的荧光传感特性，发现它可用作 pH 的有效荧光探针。由于 TICT 荧光团的非发射去激发性质，新型系统显示出低黄绿色发射，代表“开启”/“转子开启”状态。质子化的甲基哌嗪胺使 TICT 过程失稳，伴随着荧光增强，表明系统处于“开启”/“转子关闭”状态。所得结果清楚地说明了合成化合物在水溶液中作为 pH 值和粘度传感材料的巨大潜力。
