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Interaction between the π-System of Toluene and the Imidazolium Ring of Ionic Liquids: A Combined NMR and Molecular Simulation Study

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journal contribution
posted on 08.01.2009, 00:00 by Thibaut Gutel, Catherine C. Santini, Agílio A. H. Pádua, Bernard Fenet, Yves Chauvin, José N. Canongia Lopes, François Bayard, Margarida F. Costa Gomes, Alfonso S. Pensado
The solute−solvent interactions and the site−site distances between toluene and ionic liquids (ILs) 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide [BMMIm][NTf2] and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIm][NTf2] at various molar ratios were determined by NMR experiments (1D NMR, rotating-frame Overhauser effect spectroscopy (ROESY)) and by molecular simulation using an atomistic force field. The difference in behavior of toluene in these ILs has been related to the presence of H-bonding between the C2−H and the anion in [BMIm][NTf2] generating a stronger association (>20 kJ·mol−1) than in the case of [BMMIm][NTf2]. Consequently, toluene cannot cleave this H-bond in [BMIm][NTf2] which remains in large aggregates of ionic pairs. However, toluene penetrates the less strongly bonded network of [BMMIm][NTf2] and interacts with [BMMIm] cations.