物理化学学报 >> 2013, Vol. 29 >> Issue (03): 619-624.doi: 10.3866/PKU.WHXB201212102

光化学和辐射化学 上一篇    下一篇

γ辐照引发[Cnmim][NTf2]离子液体变色研究

崔振鹏, 王硕珏, 敖银勇, 彭静, 李久强, 翟茂林   

  1. 北京大学化学与分子工程学院, 北京分子科学国家实验室, 北京 100871
  • 收稿日期:2012-09-21 修回日期:2012-12-07 发布日期:2013-02-25
  • 通讯作者: 彭静, 翟茂林 E-mail:jpeng@pku.edu.cn; mlzhai@pku.edu.cn
  • 基金资助:

    国家自然科学基金(21073008, 11079007, 91126014)资助项目

Study of γ Radiation-Induced Colored Products on [Cnmim][NTf2] Ionic Liquids

CUI Zhen-Peng, WANG Shuo-Jue, AO Yin-Yong, PENG Jing, LI Jiu-Qiang, ZHAI Mao-Lin   

  1. Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P.R.China
  • Received:2012-09-21 Revised:2012-12-07 Published:2013-02-25
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21073008, 11079007, 91126014).

摘要:

1-烷基-3-甲基咪唑双三氟甲基磺酰胺型离子液体(Cnmim][NTf2])被认为是最有希望用于核燃料循环中的分离试剂之一, 虽然其化学结构在辐照过程中变化不大, 但在受到γ辐照后会发生明显的变色, 因此有必要研究该类离子液体的变色原因. 本文以60Co为辐照源, 系统研究了辐照后不同C(1)-烷基链长和咪唑环上C(2)位上的H被甲基取代后离子液体的紫外-可见(UV-Vis)吸收光谱行为, 并结合辐照后离子液体荧光光谱和质谱的变化, 分析了导致该类离子液体辐照后颜色加深的原因. 结果表明, 随着咪唑环上C(1)―烷基链长度和剂量增大, 离子液体颜色加深; 而C(2)位上的H被甲基取代后颜色明显变浅. 辐照后咪唑型离子液体的变色主要来自于辐照后产生的烷基侧链含双键的咪唑阳离子, 咪唑阳离子二聚体和含氟咪唑化合物. 此外, γ辐照引起咪唑阳离子易发生π-π堆积, 而聚集态含量增加也会引起颜色加深.

关键词: 离子液体, 辐照, 颜色, 光谱, 聚集态

Abstract:

Ionic liquids 1-alkyl-3-methylbis(trifluoromethylsulfonyl)imide ([Cnmim][NTf2]) are promising separating reagents in the nuclear fuel cycle. Their chemical structure changes slightly when exposed to γ radiation, but the apparent darkening of [Cnmim][NTf2] occurs at low dose. This radiation-induced darkening of [Cnmim][NTf2] should be investigated further. To understand the effect of radiation on [Cnmim][NTf2], we systematically studied the influences of the length of the C(1)―alkyl chain and substitution of C(2)―H on the UV-Vis spectra of irradiated [Cnmim][NTf2]. Fluorescence and mass spectra of [Cnmim][NTf2] allowed the possible colored products to be determined. The darkening of [Cnmim][NTf2] is more obvious as the length of the C(1)―alkyl chain and absorbed dose increase, but it is weakened effectively after methylation at the C(2)-position of the imidazole ring. The dominant colored products are possibly imidazolium cations containing double bonds, dimers of imidazolium cations and fluorinated imidazolium compounds. Imidazolium cations could aggregate through π-π stacking after γ-irradiation, and the associated states may also play a role in darkening these ionic liquids.

Key words: Ionic liquid, Irradiation, Color, Spectrum, Aggregation state

MSC2000: 

  • O644