Acta Chim. Sinica ›› 2015, Vol. 73 ›› Issue (8): 826-834.DOI: 10.6023/A15040252 Previous Articles     Next Articles



李婧, 曾毅, 张小辉, 于天君, 陈金平, 李嫕   

  1. 光化学转换与功能材料重点实验室 中国科学院理化技术研究所 北京 100190
  • 投稿日期:2015-04-10 发布日期:2015-05-15
  • 通讯作者: 曾毅, 李嫕;
  • 基金资助:

    项目受973计划(Nos. 2013CB834703, 2013CB834505)和国家自然科学基金(Nos. 21273258, 21233011, 21073215)资助.

Stepwise Assembly of CB[7] with Coumarin and Viologen Decorated Dendrimers and Regulation of Fluorescence Properties

Li Jing, Zeng Yi, Zhang Xiaohui, Yu Tianjun, Chen Jinping, Li Yi   

  1. Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190
  • Received:2015-04-10 Published:2015-05-15
  • Supported by:

    Project supported by the 973 Program (grant Nos. 2013CB834703, 2013CB834505) and the National Natural Science Foundation of China (grant Nos., 21273258, 21233011, 21073215).

Host-guest system is one kind of supramolecular systems. Tremendous efforts have been devoted to develop new host-guest systems extending their applications in many research fields, such as molecular machine, drug delivery, chemsensor, and tuned emission materials. The cucurbit[n]uril family is a series of synthetic macrocyclic compounds, which has shown specific self-assembly properties such as high affinity, good selectivity, and high chemostability compared with the traditional supramolecular hosts, such as cyclodextrins, crown ethers, calixarenes, and many others. In the present work, a coumarin with 7-N,N'-diethly substituent, an intramolecular charge transfer (ICT) based chromophore, was chosen as the fluorophore. The coumarin terminal-decorated polyamidoamine (PAMAM) dendrimers (Gm-2(m+1)C, m=0, 1), the coumarin and viologen-labled polyamidoamine dendrimers (EV-Gm-2(m+1)C, m=0, 1) and the coumarin and viologen model compounds (C-Model and EV) were synthesized, their structures were characterized by 1H NMR, IR and MALDI-TOF mass spectrometry. EV and each terminal coumarin group of Gm-2(m+1)C and EV-Gm-2(m+1)C assembled with cucurbit[7]uril (CB[7]) forming 1:1 inclusion complex with association constants of 3.3×106 mol-1·L and 1.4×105~1.6×105 mol-1·L. The 1H NMR study indicates that the 7-N,N'-diethly moiety along with partial coumarin ring are encapsulated into the rigid hydrophobic cavity of CB[7] forming the inclusion complex of coumarin with CB[7]. The formation of the inclusion complex of coumarin with CB[7] restricts the rotation of the N,N'-diethyl moiety, which suppresses the conversion from the emissive ICT excited state of coumarin to the nonemissive twisted intramolecular charge transfer (TICT) one, resulting in a dramatic increase of fluorescence emission. The hydrophobic microenvironment of the CB[7] cavity is also favorable to the ICT emission of coumarin. The interaction of CB[7] with EV-Gm-2(m+1)C proceeds via a stepwise mechanism. CB[7] assembles with the viologen group first and starts to form inclusion complex with coumarin when the equivalent of CB[7] exceeds that of EV. The quantity of the inclusion complex of CB[7] with coumarin can be controlled by adjusting the adding amount of CB[7], consequently, regulating the fluorescence intensity of Gm-2(m+1)C and EV-Gm-2(m+1)C. This study provides a potential strategy for developing controllable light-emitting dendritic system with efficient synthesis.

Key words: host-guest interaction, cucurbit[7]uril, coumarin, viologen, fluorescence