Intermolecular interactions in Li+-glyme and Li +-glyme-TFSA- complexes: Relationship with physicochemical properties of [Li(glyme)][TFSA] ionic liquids

Seiji Tsuzuki, Wataru Shinoda, Shiro Seki, Yasuhiro Umebayashi, Kazuki Yoshida, Kaoru Dokko, Masayoshi Watanabe

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66 Citations (Scopus)

Abstract

The stabilization energies (ΔEform) calculated for the formation of the Li+ complexes with mono-, di- tri- and tetra-glyme (G1, G2, G3 and G4) at the MP2/6-311G* level were -61.0, -79.5, -95.6 and -107.7 kcal mol-1, respectively. The electrostatic and induction interactions are the major sources of the attraction in the complexes. Although the ΔEform increases by the increase of the number of the O⋯Li contact, the ΔEform per oxygen atom decreases. The negative charge on the oxygen atom that has contact with the Li+ weakens the attractive electrostatic and induction interactions of other oxygen atoms with the Li+. The binding energies calculated for the [Li(glyme)]+ complexes with TFSA- anion (glyme=G1, G2, G3, and G4) were -106.5, -93.7, -82.8, and -70.0 kcal mol-1, respectively. The binding energies for the complexes are significantly smaller than that for the Li+ with the TFSA- anion. The binding energy decreases by the increase of the glyme chain length. The weak attraction between the [Li(glyme)]+ complex (glyme=G3 and G4) and TFSA - anion is one of the causes of the fast diffusion of the [Li(glyme)]+ complex in the mixture of the glyme and the Li salt in spite of the large size of the [Li(glyme)]+ complex. The HOMO energy level of glyme in the [Li(glyme)]+ complex is significantly lower than that of isolated glyme, which shows that the interaction of the Li + with the oxygen atoms of glyme increases the oxidative stability of the glyme. The interactions in Li+-glymes-TFSA- complexes: The interactions of Li+ with glymes (tri- and tetra-glyme) are strong (-96 and -108 kcal mol-1), while the interactions of the [Li(glyme)]+ complexes with TFSA- (-82 and -70 kcal mol-1) are weaker than that between Li+ and TFSA - (-137 kcal mol-1).

Original languageEnglish
Pages (from-to)1993-2001
Number of pages9
JournalChemPhysChem
Volume14
Issue number9
DOIs
Publication statusPublished - Jun 24 2013
Externally publishedYes

Keywords

  • geometry optimization
  • glyme complexes
  • intermolecular interactions
  • ionic liquids
  • stabilization energy

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Physical and Theoretical Chemistry

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