Evidence of C-F-P and aromatic pi-F-P weak interactions in imidazolium ionic liquids and its consequences

Panja Sumit Kumar, Srivastava Nitin, Jyoti Srivastava, Namburi Eswara Prasad, Noothalapati Hemanth, Shinsuke Shigeto, Saha Satyen

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

A simple change from alkyl group to alkene in side chain of imidazolium cation with same anion resulted in a drastic impact on physical properties (e.g., melting point) from bmimPF(6) IL to cmimPF(6) IL The underlying reasons have been elucidated by structural and interaction studies with the help of DSC, SCXRD, vibrational and multi-nuclear NMR spectroscopic techniques. Experiments reveal existence of new weak interactions involving the carbon and pi cloud of the imidazolium aromatic ring with fluoride of PF6 anion (i.e., C-2-F-P and pi-F-P) in cmimPF(6) but are absent in structurally similar prototype IL bmimPF(6). Though weak, these interactions helped to form ladder type supramolecular arrangement, resulting in quite high melting point for cmimPF(6) IL compared to bmimPF(6) IL These findings emphasize that an IL system can behave uniquely because of the existence of uncommon weak interactions. (C) 2017 Elsevier B.V. All rights reserved.
Original languageEnglish
Pages (from-to)117-125
Number of pages9
JournalSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
Volume194
DOIs
StatePublished - Apr 2018

Keywords

  • Ionic liquids (ILs)
  • Aromatic and aliphatic H-bonding interaction
  • Weak interactions
  • C-F-P interaction
  • FREQUENCY RAMAN-SPECTROSCOPY
  • DENSITY-FUNCTIONAL THEORY
  • HYDROGEN-BONDS
  • CONFORMATIONAL EQUILIBRIUM
  • VIBRATIONAL SPECTROSCOPY
  • BIOLOGICAL RECOGNITION
  • ELECTRON-DENSITY
  • INITIO CALCULATIONS
  • NMR-SPECTROSCOPY
  • DISPERSION FORCES

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