Deuteron quadrupole coupling constants and reorientational correlation times in protic ionic liquids. Issue 27 (12th April 2016)

• Record Type: Journal Article
• Authors: Strauch, Matthias; Bonsa, Anne-Marie; Golub, Benjamin; Overbeck, Viviane; Michalik, Dirk; Paschek, Dietmar; Ludwig, Ralf
• Is Part Of: Physical chemistry chemical physics. Volume 18:Issue 27(2016)
• Page Start: 17788
• Page End: 17794
• Publication Date: 2016-04-12
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c6cp01462c
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : We describe a method for the accurate determination of deuteron quadrupole coupling constants and reorientational correlation times in protic ionic liquids by means of NMR relaxations time experiments, DFT-calculations and molecular dynamics simulations. Abstract : We describe a method for the accurate determination of deuteron quadrupole coupling constants χ D for N–D bonds in triethylammonium-based protic ionic liquids (PILs). This approach was first introduced by Wendt and Farrar for O–D bonds in molecular liquids, and is based on the linear relationship between the deuteron quadrupole coupling constants χ D, and the proton chemical shifts δ 1 H, as obtained from DFT calculated properties in differently sized clusters of the compounds. Thus the measurement of δ 1 H provides an accurate estimate for χ D, which can then be used for deriving reorientational correlation-times τ ND, by means of NMR deuteron quadrupole relaxation time measurements. The method is applied to pure PILs including differently strong interacting anions. The obtained χ D values vary between 152 and 204 kHz, depending on the cation–anion interaction strength, intensified by H-bonding. We find that considering dispersion corrections in the DFT-calculations leads to only slightly decreasing χ D values. The determined reorientational correlation times indicate that the extreme narrowing condition is fulfilled for these PILs. The τ c values along with the measured viscosities provide an estimate for the volume/size of the clusters present in solution. In addition, the correlation times τ c, and the H-bonded aggregates were also characterized by molecular dynamics (MD) simulations.