Chem. J. Chinese Universities ›› 2009, Vol. 30 ›› Issue (9): 1814.

• Articles • Previous Articles     Next Articles

Microwave-Assisted Synthesis, Crystal Structure and Thermal Stability of Ionic Liquid 1-sec-Butyl-3-methylimidazolium Hexfluorophosphate

ZHAO Ya-Mei, HU Xiao-Ling*, GUAN Ping, LI Da-Peng   

  1. Department of Applied Chemistry, School of Natural and Applied Sciences, Northwestern Polytechnical University, Xi′an 710072, China
  • Received:2008-10-13 Online:2009-09-10 Published:2009-09-10
  • Contact: HU Xiao-Ling. E-mail: huxl@nwpu.edu.cn
  • Supported by:

    国家自然科学基金(批准号: 50572089)资助.

Abstract:

In this paper, 1-sec-butyl-3-methylimidazolium hexfluorophosphate([s-bmim][PF6]) was synthesized with the aid of microwave. Large single crystals were formed in the water-ethanol-toluene system[V(water)∶V(ethanol)∶V(toluene)=0.16∶2.84∶7]. The large single crystals are stable under the air and moisture, with the maximum length of 11 mm. The crystal structure was determined by X-ray diffraction. [s-bmim][PF6] crystallizes in the monoclinic space group P21/m, with unit-cell parameters a=0.9042(4) nm, b=0.8213(3) nm, c=0.9775(4) nm, γ=116.618°(6), Z=2, V=64.909(4) nm3, Dc=1.454 g/cm3, μ=0.265 mm-1, F(000)=292, the final R=0.0998, wR=0.2656. In the structure, the cations and anions can not form neutral ion pairs owing to the interionic interactions such as the dominant Coulombic attraction, the weak hydrogen bonds and the non-chemical-bond tension of cation-cation. Moreover, it was found that introducing the sec-butyl chain could change the asymmetry of cations and inhibit the rotation of the alky chains of [s-bmim][PF6]. The branched structure leads to the void space filling in the crystal stacking and high lattice energy. Finally, the thermal stability of [s-bmim][PF6] was discussed.

Key words: Ionic liquid; Microwave synthesis; Crystal structure; Thermal stability

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