Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (03): 619-624.doi: 10.3866/PKU.WHXB201212102

• PHOTOCHEMISTRY AND RADIATION CHEMISTRY • Previous Articles     Next Articles

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).

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