Structural analysis of ionic liquids with symmetric and asymmetric fluorinated anions

Man Zhao; Boning Wu; Sharon I Lall-Ramnarine; Jasodra D Ramdihal; Kristina A Papacostas; Eddie D Fernandez; Rawlric A Sumner; Claudio J Margulis; James F Wishart; Edward W Castner Jr

doi:10.1063/1.5111643

Structural analysis of ionic liquids with symmetric and asymmetric fluorinated anions

J Chem Phys. 2019 Aug 21;151(7):074504. doi: 10.1063/1.5111643.

Affiliations

¹ Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA.
² Chemistry Department, Queensborough Community College of the City University of New York, Bayside, New York 11364, USA.
³ Department of Chemistry, The University of Iowa, Iowa City, Iowa 52242, USA.
⁴ Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973, USA.

PMID: 31438705
DOI: 10.1063/1.5111643

Abstract

Ionic liquids (ILs) with relatively low viscosities and broad windows of electrochemical stability are often constructed by pairing asymmetric cations with bisfluorosulfonylimide (FSI^-) or bistriflimide (NTf₂ ^-) anions. In this work, we systematically studied the structures of ILs with these anions and related perfluorobis-sulfonylimide anions with asymmetry and/or longer chains: (fluorosulfonyl)(trifluoromethylsulfonyl)imide (BSI_0,1 ^-), bis(pentafluoroethylsulfonyl)imide (BETI^-), and (trifluoromethylsulfonyl) (nonafluorobutylsulfonyl)imide (BSI_1,4 ^-) using high energy X-ray scattering and molecular dynamics simulation methods. 1-alkyl-3-methylimidazolium cations with shorter (ethyl, Im_2,1 ⁺) and longer (octyl, Im_1,8 ⁺) hydrocarbon chains were selected to examine how the sizes of nonpolar hydrocarbon and fluorous chains affect IL structures and properties. In comparison with these, we also computationally explored the structure of ionic liquids with anions having longer fluorinated tails.