Gwaro Caroline, Ndung'U Caroline, Bobadova-Parvanova Petia, Goliber Dylan, Do Quynh, Walker Ashley R, Murders Evan, LaMaster Daniel, Fronczek Frank R, Garno Jayne, Vicente Maria da Graça H
Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States.
Department of Chemistry and Fermentation Sciences, Appalachian State University, Boone, North Carolina 28608, United States.
ACS Omega. 2025 Apr 7;10(15):14723-14737. doi: 10.1021/acsomega.4c08799. eCollection 2025 Apr 22.
A series of boron dipyrromethene (BODIPY) dyes were nitrated in high yields using nitronium tetrafluoroborate at positions 2, 3, and 2,6 of the BODIPY core. This method allows for the regioselective nitration of the pyrrolic positions under milder conditions than previously reported methods. The photophysical properties and electronic transitions of these BODIPYs were investigated by using UV-vis spectroscopy, fluorescence spectroscopy, and density-functional theory (DFT) calculations. The introduction of one nitro group dramatically increases the dipole moment of the molecule, induces marked blue shifts in the absorption and emission bands, decreases the molar absorptivity, and increases the Stokes shifts of the BODIPYs. When a second nitro group is symmetrically introduced, the calculated dipole moments of the BODIPYs decrease in both the ground and excited states. Our studies show that the spectroscopic and self-assembly properties of nitro-substituted BODIPYs are highly dependent on solvent polarity and polarizability. In a polar organic solvent, nitro-substitution tends to quench the characteristic fluorescence of BODIPYs, while in a nonpolar solvent, significantly higher absolute fluorescence quantum yields are observed. On the other hand, aggregates are formed in aqueous solution, as observed by atomic force microscopy (AFM). Our results suggest a potential application of nitro-BODIPYs as polarity sensors.
使用四氟硼酸硝鎓，一系列硼二吡咯亚甲基（BODIPY）染料在BODIPY核的2、3位以及2、6位被高产率硝化。该方法能够在比先前报道的方法更温和的条件下对吡咯位置进行区域选择性硝化。通过紫外可见光谱、荧光光谱和密度泛函理论（DFT）计算研究了这些BODIPY的光物理性质和电子跃迁。引入一个硝基会显著增加分子的偶极矩，导致吸收和发射带明显蓝移，降低摩尔吸光率，并增加BODIPY的斯托克斯位移。当对称引入第二个硝基时，BODIPY在基态和激发态的计算偶极矩均减小。我们的研究表明，硝基取代的BODIPY的光谱和自组装性质高度依赖于溶剂的极性和极化率。在极性有机溶剂中，硝基取代往往会淬灭BODIPY的特征荧光，而在非极性溶剂中，则观察到明显更高的绝对荧光量子产率。另一方面，如通过原子力显微镜（AFM）观察到的，在水溶液中会形成聚集体。我们的结果表明硝基-BODIPY作为极性传感器具有潜在应用。
