Acta Chimica Sinica ›› 2012, Vol. 70 ›› Issue (24): 2501-2506.DOI: 10.6023/A12090695 Previous Articles     Next Articles



顾志国a,b, 王宝祥a, 庞春燕a, 周文a, 李在均a   

  1. a 江南大学化学与材料工程学院 无锡 214122;
    b 南京大学配位化学国家重点实验室 南京 210093
  • 投稿日期:2012-09-21 发布日期:2012-11-29
  • 通讯作者: 顾志国
  • 基金资助:
    项目受国家自然科学基金(No. 21101078)、新世纪优秀人才计划(No. NCET-11-0657)、江苏省自然科学基金(No. BK2011143)、中央高校基本科研业务费专项资金(No. JUSRP21111)和南京大学配位化学国家重点实验室开放基金资助.

Syntheses, Characterization and Fluorescent Properties of Lanthanide-Containing Ionic Liquids [Cnmim][Ln(NO3)4]

Gu Zhiguoa,b, Wang Baoxianga, Pang Chunyana, Zhou Wena, Li Zaijuna   

  1. a School of Chemistry and Material Engineering, Jiangnan University, Wuxi 214122;
    b State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093
  • Received:2012-09-21 Published:2012-11-29
  • Supported by:
    Project supported by the National Natural Science Foundation of China (No. 21101078), the Program for New Century Excellent Talents in University of China (No. NCET-11-0657), the Natural Science Foundation of Jiangsu Province (No. BK2011143), the Fundamental Research Funds for the Central Universities (No. JUSRP21111) and the State Key Laboratory of Coordination Chemistry of Nanjing University.

Five kinds of ionic liquids 1-alkyl-3-methylimidazolium nitrate [Cnmim]NO3 (n=2, 4, 6, 8, 10; mim=N-methylimidazolium) were synthesized from N-methylimidazolium, alkyl bromides and sodium nitrate. The structures of ionic liquids were characterized and analyzed by infrared spectra (IR), proton nuclear magnetic resonance (1H NMR), mass spectrometry (MS) and elemental analyses (EA). Lanthanide-containing ionic liquids [Cnmim][Ln(NO3)4] (Ln=Eu, Tb) were prepared by reactions of 1-alkyl-3-methylimidazolium nitrate and europium nitrate/terbium nitrate in 1∶1 molar ratio. [Cnmim][Ln(NO3)4] were all sticky liquids at room temperature. The strength of nitrate absorption peaks of [Cnmim][Ln(NO3)4] in the IR spectra was stronger than [Cnmim]NO3 which indicated that the coordination of nitrate anions to lanthanide ions enhanced the nitrate absorption peaks. The structures of [Cnmim][Ln(NO3)4] contained 1-alkyl-3-methylimidazolium cations and [Ln(NO3)4]- anions in which each lanthanide ion was coordinated with eight oxygen atoms from four nitrate ions were further confirmed by ESI mass spectrometry. The thermal decomposition of [Cnmim]NO3 and [Cnmim][Ln(NO3)4] were investigated by thermogravimetric analysis (TGA), which indicated that all the compounds represented high stability until ca. 250 ℃. Under UV lamp irradiated at 365 nm, [Cnmim][Eu(NO3)4] and [Cnmim][Tb(NO3)4] showed red and green fluorescence, respectively, which indicated that these lanthanide-containing ionic liquids could be used as good soft luminescent materials. The photoluminescence properties of the lanthanide-containing ionic liquids were studied at room temperature in water by measuring emission and excitation spectra. These experiments demonstrated that the solution of [Cnmim][Ln(NO3)4] (Ln=Eu, Tb) showed strong characteristic fluorescence. The red fluorescence of [Cnmim][Eu(NO3)4] was assigned to Eu3+ 5D0-7F2 transition at 617 nm, while the green fluorescence of [Cnmim][Tb(NO3)4] was assigned to Tb3+ 5D4-7F5 transition at 545 nm. Temperature and concentration influenced the solution fluorescence intensity of [Cnmim][Ln(NO3)4]. Due to the intermolecular collision intensified in solution with temperature increasing, the fluorescence intensity of [Cnmim][Ln(NO3)4] decreased. Fluorescence intensity increased with the concentration increasing, while fluorescence quenching phenomenon appeared when exceeded a certain concentration.

Key words: ionic liquids, lanthanide, syntheses, characterization, fluorescence