A new coumarin derivative containing both imine bond and amide moiety was synthesised. It was used as a reaction‐based pH probe and was sensitive to pH changes in the intervals 1.50–4.10 and 10.20–12.86. In the pH range 1.50–4.10, the ultraviolet‐visible (UV‒vis) absorption band of the probe gradually shifted from 353 nm to 340 nm with decrease in the pH value. The colour changed from pale yellow fluorescence at pH 4.10 to blue fluorescence at pH 1.50. Meanwhile the fluorescence emission band at 501 nm gradually shifted to 560 nm accompanying a gradual enhancing in the emission intensity. This pH response is caused by the hydrolysis of the imine bond in the probe under acidic conditions (pH 1.50–4.10). The colourless probe solution turned yellow at pH range 10.20–12.86. Bathochromic shift of the fluorescence band from 501 nm gradually to 550 nm was observed with the increase of pH value from 10.20 to 12.86 accompanying a gradual enhancement of the fluorescence emission intensity, indicating that the new compound serves as a fluorescent pH probe at pH range 10.20–12.86 through a deprotonation process. Under strongly alkaline conditions with pH larger than 12.86, hydrolysis of the lactone structure in the probe occurred to produce non‐fluorescent species.

中文翻译：

---

一种基于反应的新型荧光探针，可对多个时间段的pH变化敏感

合成了同时包含亚胺键和酰胺部分的新香豆素衍生物。它被用作基于反应的pH探针，并且在1.50–4.10和10.20–12.86的间隔内对pH变化敏感。在pH值1.50–4.10范围内，随着pH值的降低，探头的紫外可见（UV‒vis）吸收带逐渐从353 nm移至340 nm。颜色从pH 4.10的浅黄色荧光变为pH 1.50的蓝色荧光。同时，随着发射强度的逐渐增强，在501nm处的荧光发射带逐渐移至560nm。pH响应是由于在酸性条件（pH 1.50–4.10）下探针中亚胺键的水解引起的。无色探针溶液在pH范围10.20–12.86时变为黄色。随着pH值从10.20增加到12.86，伴随着荧光发射强度的逐渐增强，观察到荧光带从501nm逐渐向550nm的红移，表明该新化合物在pH范围为10.20时用作荧光pH探针。 –通过反质子化过程获得了–12.86。在pH大于12.86的强碱性条件下，探针中的内酯结构发生水解，产生非荧光物质。