Investigation of the interactions between 1-butyl-3-methylimidazolium-based ionic liquids and isobutylene using density functional theory

Xiaoning Li; Wenli Guo; Yibo Wu; Wei Li; Liangfa Gong; Xiaoqian Zhang; Shuxin Li; Yuwei Shang; Dan Yang; Hao Wang

doi:10.1007/s00894-018-3586-y

Investigation of the interactions between 1-butyl-3-methylimidazolium-based ionic liquids and isobutylene using density functional theory

J Mol Model. 2018 Mar 6;24(4):83. doi: 10.1007/s00894-018-3586-y.

Authors

Xiaoning Li^{1

2

3}, Wenli Guo^{4

5

6}, Yibo Wu^{7

8}, Wei Li^{2

3}, Liangfa Gong^{2

3}, Xiaoqian Zhang^{1

2

3}, Shuxin Li^{2

3}, Yuwei Shang^{2

3}, Dan Yang^{2

3}, Hao Wang^{2

3}

Affiliations

¹ College of Material Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, China.
² Department of Materials Science and Engineering, Beijing Institute of Petrochemical Technology, Beijing, 102617, China.
³ Beijing Key Lab of Special Elastomeric Composite Materials, Beijing, 102617, China.
⁴ College of Material Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, China. gwenli@bjzx.gov.cn.
⁵ Department of Materials Science and Engineering, Beijing Institute of Petrochemical Technology, Beijing, 102617, China. gwenli@bjzx.gov.cn.
⁶ Beijing Key Lab of Special Elastomeric Composite Materials, Beijing, 102617, China. gwenli@bjzx.gov.cn.
⁷ Department of Materials Science and Engineering, Beijing Institute of Petrochemical Technology, Beijing, 102617, China. wuyibo@bipt.edu.cn.
⁸ Beijing Key Lab of Special Elastomeric Composite Materials, Beijing, 102617, China. wuyibo@bipt.edu.cn.

PMID: 29508128
DOI: 10.1007/s00894-018-3586-y

Abstract

To identify ionic liquids (ILs) that could be used as solvents in isobutylene (IB) polymerization, the interactions between IB and eight different ILs based on the 1-butyl-3-methylimidazolium cation ([Bmim]⁺) were investigated using density functional theory (DFT). The anions in the ILs were chloride, hexafluorophosphate, tetrafluoroborate, bis[(trifluoromethyl)sulfonyl]imide, tetrachloroaluminate ([AlCl₄]^-), tetrachloroferrate, acetate, and trifluoroacetate. The interaction geometries were explained by changes in the total energy, intermolecular distances, Hirshfeld charges, and the electrostatic potential surface. The IL solvents were screened by comparing their interaction intensities with IB to the interaction intensities of reference ILs ([AlCl₄]^--based ILs) with IB. The microscopic mechanism for IB dissolution was rationalized by invoking a previously reported microscopic mechanism for the dissolution of gases in ILs. Computation results revealed that hydrogen (H) bonding between C2-H on the imidazolium ring and the anions plays a key role in ion pair (IP) formation. The addition of IB leads to slight changes in the dominant interactions of the IP. IB molecules occupied cavities created by small angular rearrangements of the anions, just as CO₂ does when it is dissolved in an IL. The limited total free space in the ILs and the much larger size of IB than CO₂ were found to be responsible for the poor solubility of IB compared with that of CO₂ in the ILs.

Keywords: Density functional theory; Interactions; Ionic liquids; Isobutylene; Molecular modeling.