Acta Chimica Sinica ›› 2014, Vol. 72 ›› Issue (11): 1157-1163.DOI: 10.6023/A14100694 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:2014-10-09 发布日期:2014-10-22
  • 通讯作者: 曾毅, 李嫕;
  • 基金资助:

    项目受科技部国家重点基础研究发展计划(Nos. 2013CB834703, 2013CB834505)和国家自然科学基金(Nos. 21273258, 21173245, 21233011, 21073215)资助.

Regulation of Photophysical Properties for Naphthyl Decorated PAMAM Dendrimers by Pseudorotaxane Formation at Periphery

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:2014-10-09 Published:2014-10-22
  • Supported by:

    Project supported by the 973 Program (Grant Nos. 2013CB834703, 2013CB834505) and the National Natural Science Foundation of China (Grant Nos. 21273258, 21173245, 21233011, 21073215).

Dendrimers are regularly and hierarchically branched synthetic macromolecules with monodispersity, globular shape, interior pockets, and numerous peripherial functionality, which endow them with great potential in miscellaneous applications such as host-guest chemistry, chemosensor, catalysis, drug delivery, microreactor and light-harvesting systems. In the present work, a series of naphthyl terminal-decorated polyamidoamine (PAMAM) dendrimers Gn-NA (n=1~3) and model compound were synthesized. The water-soluble PAMAM backbone was constructed by the classic divergent method and the terminal modification of dendrimers by naphthyl groups was accomplished through a reaction of peripheral amino units with naphthyl succinimidyl ester efficiently. The average functionalization extents of the peripheral groups were 100%, 97% and 93% for G1~G3, respectively. The structures of Gn-NA (n=1~3) were characterized by 1H NMR, 13C NMR, MALDI-TOF mass spectra and IR. Steady state and time-resolved photophysical studies reveal that strong interactions among peripheral naphthyls occur within Gn-NA, resulting in the excimer formation and the naphthyl fluorescence quenching. The quenching efficiency of naphthyl fluorescence increases with increasing generations. The assembly of the peripheral naphthyl group with cucurbit[7]uril (CB[7]) forms a pseudorotaxane with ratio of 1:1 and association constants (an application of B-H equation) of 768, 887 and 823 mol-1·L from generation 1 to generation 3, respectively. The lifetime of the pseudorotaxane of NA-Model with CB[7] is slightly longer than that of NA-Model, indicating that the formation of pseudorotaxane can reduce the nonradiative decay at a certain degree. The lifetimes of naphthyl group and its pseudorotaxane with CB[7] of Gn-NA were resolved to be 2.5~2.7 and 11.4~11.7 ns, respectively, and the lifetimes of the intramolecular naphthyl excimer of Gn-NA were analyzed to be ca. 17 ns. Combining the results of the remarkably increased lifetime of the naphthyl group in its pseudorotaxane form and those of the NA-Model system, we conclude that the peripheral pseudorotaxane formation depresses both the formation of intramolecular naphthyl excimer and the excited state quenching by solvent, thus enhancing the fluorescence emission of naphthyl dramatically. This study provides a potential strategy for developing controllable light-emitting dendritic system with efficient synthesis and improvable photophysical properties.

Key words: PAMAM dendrimer, cucurbit[7]uril, pseudorotaxane, photophysical property