AbstractChemical fine‐tuning of fluorophores is a pivotal step towards development of next generation fluorescent dyes for microscopy. With the advent of high‐resolution two‐photon excitation fluorescence imaging, there is a growing demand for very sensitive laser dyes that can be efficiently excited using commercial Ti:sapphire laser sources in the first near‐infrared window (NIR‐I, 780–1020 nm). Using the fluorescent dye Nile Red as the lead structure, we report a robust and concise Suzuki coupling approach for the synthesis of 14 new Nile Red analogues that feature extended π ring systems and diverse functionalities. For this set, we gauged their two‐photon excitation efficiency in NIR‐I as well as evaluated their general fluorescent properties (emission wavelength, Stokes shift, quantum yield and solvatochromism). Several of the new fluorophores were found to display very favorable characteristics. In particular, the derivative featuring a 4‐aminophenyl group in the 2‐position of Nile Red exhibited extreme solvent sensitivity, and the thien‐2‐yl substituted Nile Red derivative showed significantly redshifted emission, large Stokes shift and high two‐photon brightness.
摘要荧光团的化学微调是开发用于显微镜的下一代荧光染料的关键步骤。随着高分辨率双光子激发荧光成像技术的出现,对能在第一近红外窗口(NIR-I,780-1020 nm)使用商用钛:蓝宝石激光源高效激发的高灵敏度激光染料的需求日益增长。以荧光染料尼罗河红为先导结构,我们报告了一种稳健简洁的铃木偶联方法,用于合成 14 种新的尼罗河红类似物,这些类似物具有扩展的 π 环系统和多种功能。对于这组类似物,我们测定了它们在近红外 I 波段的双光子激发效率,并评估了它们的一般荧光特性(发射波长、斯托克斯位移、量子产率和溶解色度)。研究发现,几种新的荧光团显示出非常有利的特性。其中,尼罗红 2 位上含有 4- 氨基苯基的衍生物表现出极高的溶剂敏感性,而噻吩-2-基取代的尼罗红衍生物则表现出明显的红移发射、较大的斯托克斯位移和较高的双光子亮度。