化学学报 ›› 2013, Vol. 71 ›› Issue (9): 1257-1264.DOI: 10.6023/A13040352 上一篇    下一篇

研究论文

十字架型间二咪唑(鎓)苯的合成及对有机酸的识别

王志, 周红军, 胡俊毅, 游劲松, 高戈   

  1. 四川大学化学学院 成都 610065
  • 投稿日期:2013-04-01 发布日期:2013-06-27
  • 通讯作者: 游劲松,E-mail:jsyou@scu.edu.cn;高戈,E-mail:gg2b@scu.edu.cn E-mail:jsyou@scu.edu.cn;gg2b@scu.edu.cn
  • 基金资助:

    项目受国家自然科学基金(Nos. 20902063, 21172159)和国家教育部留学回国人员科研启动基金(No. 20111568-8-2)资助.

Bisimidazole and Bisimidazolium Cruciforms: Synthesis and Discrimination of Organic Acids

Wang Zhi, Zhou Hongjun, Hu Junyi, You Jingsong, Gao Ge   

  1. College of Chemistry, Sichuan University, Chengdu 610065
  • Received:2013-04-01 Published:2013-06-27
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Nos. 20902063, 21172159) and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (No. 20111568-8-2).

通过Sonogashira偶联反应、N-芳基化反应和季铵化反应, 我们构筑了一类基于咪唑(鎓)的十字架型荧光分子45, 研究了烷基链以及咪唑和咪唑鎓分别作为电子受体对十字架型分子荧光性质的影响. 其中, 分子4a具有较高的荧光量子产率和大的斯托克斯位移; 在不同极性的溶剂中表现出明显的溶致变色性质, 荧光颜色覆盖由深蓝色到黄色区域; 同时, 该分子还具有明显的聚集诱导发光特性. 我们采用数码照相的方法代替繁琐的荧光光谱仪, 仅使用单一该荧光分子在两种有机溶剂中即可通过荧光颜色有效区分15种结构类似或pKa相近的有机酸. 最后, 分子4a5a固载于硅胶板上通过可逆的荧光颜色变化实现了对HCl/Et3N气体的识别.

关键词: 咪唑, 咪唑鎓, 十字架型荧光分子, 溶致变色, 聚集诱导发光, 识别

Bisimidazole cruciforms 4a&b based on 1,3-di(imidazol-1-yl)-benzene were synthesized in good yields via the Sonogashira coupling of 1,5-dibromo-2,4-diiodobenzene with 4-ethynyl-N,N-dimethylaniline and 4-ethynyl-N,N-dibutyl- aniline followed by the N-arylation with imidazole. Further quaternization of 4 with iodomethane afforded bisimidazolium cruciforms 5a&b. As an example, the didonor-π-diacceptor cruciform 4a showed strong solvatochromism that its emission colors varied from deep blue (toluene: 422 nm) to yellow (DMSO: 516 nm) in different organic solvents. The Stokes shift of 4a in acetonitrile was as large as 148 nm, which could suppress the fluorescence quench caused by reabsorption. The single bond connected multi-aromatic system made cruciform 4a possess aggregation-induced emission (AIE) property. A 12-fold enhancement of the fluorescence was observed for the solution of 4a in methanol/water (70:30, V/V) compared with in methanol/water (50:50, V/V). Taking advantage of the digital photography technology, fifteen carboxylic acids having either similar pKa values or similar structures were distinguished well by using bisimidazole cruciform 4a as the only indicator in two solvents. However, bisimidazolium cruciforms 5 could not discriminate them. All analytes were dissolved in dichloromethane and acetonitrile. A 20 μL of dilute stock solution of 4a was added into 2.0 mL of each such solution. The solutions were well-mixed and subjected to the UV illumination (365 nm). Photos were then taken using a digital camera one by one. The square segments representative of the emission colors were cut out and arranged into arrays for naked-eye discrimination. These emission colors were later converted into numerical R/G/B values by using Adobe PhotoShop. The standard deviations σs were calculated for the R/G/B value of the solution of 4a with each analyte towards those with the other analytes, which represented the degrees of discrimination between two analytes. The standard deviations σ's were calculated for the R/G/B values of the solutions of 4a with different analytes towards that of the blank solution of 4a, which represented the degrees of the color variation caused by the recognition. Comparing with traditional fluorescence sensing method, the present method is simple, efficient and time-saving. Bisimidazole cruciform 4a emitted solid-state florescence of green-yellow color with a quantum yield of 0.33 while bisimidazolium cruciform 5a emitted pure red color with a quantum yield of 0.14. They exhibited reversible color change under the UV irradiation when contacted with HCl and Et3N vapors, indicating they could serve as solid sensors for acid vapors. The fluorescence study also showed that the alkyl chains significantly affect the solid-state fluorescence of bisimidazolium cruciform 5.

Key words: imidazole, imidazolium, cruciform fluorophore, solvatochromism, aggregation-induced emission, sensing