具有ESIPT性质的苯并三氮唑类紫外光稳定剂的研究

苯并三氮唑类衍生物因具有独特的化学结构,其光化学与光物理研究引起人们的关注。笔者介绍了苯并三氮唑类衍生物作为紫外光稳定剂的特点、种类、研究现状以及应用,指出了苯并三氮唑类衍生物的激发态分子内质子转移(ESIPT)的机制,并分析了这类化合物目前研究中存在的问题及以后研究的方向。     

4-Formyl-2-（2H-benzotriazol-2-yl）-phenol： an ESIPT chromophore

In the present work, excited state intramolecular proton transfer （ESIPT） emission properties of a new benzotriazole derivative 4-formyl-2-（2H-benzotriazol-2-yl）- phenol （C1） were studied. 4-Formyl-2-（2H-benzotriazol-2- yl）-methoxy-benzene （C2）, 4-formyl-2-（2H-benzotriazol-2- yl）-phenyl acetate （C3） and 4-methyl-2-（2H-benzotriazol- 2-yl）-phenol （C4） were used as the reference molecules. ^1H NMR chemical shift of hydroxy group in C1 was located at more down field than that of C4 or p-hydroxy-benzaldehyde （C5）, respectively. C1 showed two absorption bands in the range of 260-400 nm zones in various solvents, while C2 and C3 exhibited single absorption band. The equal molar mixtures of C2/C5 or C3/C5 showed single absorption band. C2 and C3 displayed single fluorescence emission band in various solvents, while C1 exhibited dual emission bands in some strong polar solvents. Furthermore, the second emission band in these strong polar solvents showed the large Stokes shift. The results show that the second emission band of C1 was produced by ESIPT. C2 and C3 could not undergo ESIPT due to no hydroxy group. The geometry optimization calculation of enol and keto forms in the ground and excited states of C1 provided tough theoretical evidences of ESIPT.