Aromatic 2-(2′-hydroxyphenyl)benzoxazole esters: a novel class of caged photoluminescent dyes
作者:Christoph Kocher、Paul Smith、Christoph Weder
DOI:10.1039/b202719b
日期:——
Esterification of the photoluminescent 2-(2â²-hydroxyphenyl)benzoxazole (HPBO) with aromatic acids has led to a novel family of apolar, non-ionic âcagedâ photoluminescent dyes. The esters are not photoluminescent, but upon exposure to appropriate UV radiation, the ester bond is cleaved and the photoluminescent HPBO is quantitatively restored. This photoactivation process follows first order reaction kinetics, with quantum yields between 7 and 38%, depending on the nature of the photocleavable ester group. The esterification of HPBO induces a significant hypsochromic shift in the absorption spectrum of the chromophore, creating a wavelength region in which the activated HPBO can be excited, while the HPBO-ester remains caged. Thus, the caged/uncaged dye pairs can be developed and detected with high selectivity. HPBO esters further offer the advantage of high thermal stability, which renders them useful for application in melt-processed
polymer blends. This possibility was exploited in the production of photoluminescent images in polymer films, and in the visualization of flow patterns in a polymer melt.
光致发光的 2-(2â²-羟基苯基)苯并恶唑(HPBO)与芳香族酸的酯化反应催生了一系列新型非极性、非离子型 "笼式 "光致发光染料。这些酯类不发光,但在适当的紫外线照射下,酯键会裂解,光致发光的 HPBO 会定量恢复。这种光激活过程遵循一阶反应动力学,量子产率在 7% 到 38% 之间,具体取决于可光裂解酯基的性质。HPBO 的酯化会导致发色团的吸收光谱发生显著的低色度偏移,从而产生一个波长区域,在该区域中,活化的 HPBO 可以被激发,而 HPBO 酯仍处于笼状状态。因此,笼型/非笼型染料对可以以高选择性进行开发和检测。HPBO 酯还具有热稳定性高的优点,可用于熔融加工的聚合物混合物中。在制作聚合物薄膜中的光致发光图像以及聚合物熔体中流动模式的可视化过程中,我们就利用了这种可能性。