A new type of a highly fluorescent sulforhodamine dye, 221SR, was designed and synthesized using 7-azabicylco[2.2.1]heptyl moieties as the electron donating auxochrome groups. Using the prototypical dye tetramethylsulforhodamine, TMSR, as a benchmark, we show this new dye has higher fluorescent quantum yields, Phi, (Phi = 0.95 vs Phi = 0.65 at 20 degrees C), emission efficiencies that are invariant in the 20--> 60 degrees C temperature range (Phi = 0.95 vs Phi = 0.38 at 60 degrees C), and fluorescence lifetimes that increase with a rise in temperature (20 --> 60 degrees C) as compared to a decrease for the benchmark dye (3.8 --> 3.9 vs 2.8 --> 1.7 ns). Importantly, photostability studies found the azabicyclic rhodamine to be many times more stable than its tetramethyl analogue. To the best our knowledge this is the first report of the use of an apex-N-substituted azabicycloalkane as an electron donor group in any class of donor-acceptor dye. Thus, the concept of using an apex-substitutes bicyclic amine as a donor moiety constitutes a new paradigm for simultaneously inducing remarkable beneficial effects on both emission efficiency and photostability in a donor-acceptor fluorophore.

中文翻译：

---

7-氮杂双环[2.2.1]庚烷作为独特且有效的二烷基氨基助色剂部分：在荧光罗丹明染料中的演示

使用7-氮杂双环[2.2.1]庚基部分作为给电子辅助色素基团，设计并合成了一种新型的高荧光磺基罗丹明染料221SR。使用原型染料四甲基磺基罗丹明 (TMSR) 作为基准，我们表明这种新染料具有更高的荧光量子产率 Phi（Phi = 0.95 与 Phi = 0.65 在 20 摄氏度），发射效率在 20--> 60 摄氏度的温度范围（Phi = 0.95 与 Phi = 0.38 在 60 摄氏度），荧光寿命随着温度的升高（20 --> 60 摄氏度）而增加，而基准染料的荧光寿命则下降（3.8 - -> 3.9 与 2.8 --> 1.7 ns）。重要的是，光稳定性研究发现氮杂双环罗丹明比其四甲基类似物稳定许多倍。据我们所知，这是在任何类别的供体-受体染料中使用顶点-N-取代的氮杂双环烷烃作为电子供体基团的第一份报告。因此，使用顶点取代双环胺作为供体部分的概念构成了一种新范式，可同时对供体-受体荧光团的发射效率和光稳定性产生显着的有益影响。