Structure and vibrational features of the protic ionic liquid 1,8-diazabicyclo[5.4.0]-undec-7-ene-8-ium bis(trifluoromethanesulfonyl)amide, [DBUH][TFSI]

TitleStructure and vibrational features of the protic ionic liquid 1,8-diazabicyclo[5.4.0]-undec-7-ene-8-ium bis(trifluoromethanesulfonyl)amide, [DBUH][TFSI]
Publication TypeArticolo su Rivista peer-reviewed
Year of Publication2021
AuthorsTriolo, A., Paolone A., Sarra A., Trequattrini F., Palumbo O., Appetecchi Giovanni Battista, F. Celso Lo, Chater P., and Russina O.
JournalJournal of Molecular Liquids
ISSN01677322
KeywordsAmides, Bis(trifluoromethane sulfonyl)imide, DFT calculation, Far-ir spectroscopy, Hydrogen, Hydrogen bonds, Ionic liquids, IR-spectroscopy, molecular dynamics, Neutralisation, Protic ionic liquids, Strongest acid, Structure features, Vibrational features, X -ray scattering, X ray scattering
Abstract

The Protic Ionic Liquid (PIL) formed by neutralization of the super-strong base 1,7-diazabicyclo[5.4.0]undec-7-ene (DBU) with the super-strong acid bis(trifluoromethanesulfonyl)-imide (TFSI), indicated as [DBUH][TFSI], has been investigated. Its chemical physical properties and structural features have been explored using a synergy of experimental and computational tools. Molecular Dynamics-rationalised X-ray diffraction patterns highlight the major role played by hydrogen bonding (HB) in affecting morphology in this PIL. A comparison between HB features in this and in related PILs has been presented, on the base of far-IR experiments and DFT analysis. Indications of a weaker HB interaction in [DBUH][TFSI] in comparison with [DBUH][TfO], consistently with their ΔpKa difference, have been observed and rationalised in terms of geometrical properties of the main conformers contributing to the experimental spectra. In the liquid phase of [DBUH][TFSI] a particularly large conformational disorder is observed and the corresponding large dispersion of the frequencies of the HB stretching modes leads to a broad absorption band without a well defined peak. On the contrary, well detectable HB related absorptions are observable in the solid phase of [DBUH][TFSI] and at all temperatures in [DBU][TfO], where less configurational disorder occurs. © 2021 Elsevier B.V.

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URLhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-85119004555&doi=10.1016%2fj.molliq.2021.117981&partnerID=40&md5=74e942d2cdda0d1dab37ac6027d6a95b
DOI10.1016/j.molliq.2021.117981