荧光素衍生物的pH敏感性及其光稳定性的研究

Research on pH sensitivity of fluorescein derivatives and its photostabilities

摘要:

采用Diels-Alder反应，以4-卤代（氟、氯、溴）间苯二酚与邻苯二甲酸酐为原料，在甲基磺酸为催化剂下合成了2’,7’-二卤代荧光素（DFF，DCF，DBF）。对化合物的结构进行了表征。pH滴定实验表明，化合物(DFF，DCF，DBF)的紫外吸收与荧光发射光谱均对溶液的pH有较强的敏感性。DFF、DCF、DBF分别在490、502、505 nm处的吸收强度和在517、526、530 nm处的荧光强度随着pH增加而增大；当溶液的pH > 10后，吸收强度与荧光基本保持不变。结果显示，DFF、DCF和DBF的热力学常数pKa值依次增大，分别是4.7、5.1、6.6；而荧光量子产率却依次减小，分别是0.97、0.94、0.67。光降解实验结果表明化合物的光稳定性大小依次是DFF > DCF > FL (荧光素) > DBF。

Abstract:

In this paper, 2’,7’-dihalofluorescein (DFF, DCF and DBF) were synthesized by the Diels-Alder reaction of 4-haloresorcinol with phthailc anhydride in the persence of methanesulfonic acid as catalyzer, and their structures were characterized. The pH titrations indicate that the dependences of fluorescent properties for these compounds on pH were extremely sensitive in the absorption spectra and the fluorescence spectra. The absorption intensities at 490, 502 and 505 nm, and the fluorescent intensities at 517, 526 and 530 nm in DFF, DCF and DBF increased with pH increasing, respectively. When the pH > 10, the absorption intensities and fluorescent intensities slightly decreased and then kept constant. The result shows that the thermodynamic pKa values and fluorescence quantum yields of DFF, DCF and DBF are 4.7, 5.1 and 6.6, and 0.97, 0.94 and 0.67, respectively. The photodegradation experiment indicated that photostabilities were DFF﹥DCF﹥FL﹥DBF in order.