The effect of tributylphosphate and tributyl phosphine oxide on hydrogen bonding interactions between water and the 1-ethyl-3-methylimidazolium cation in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Abstract

We have used attenuated total reflectance FTIR and NMR spectroscopies to study the hydrogen bonding interactions of tributylphosphate (TBP) and tributylphosphine oxide (TBPO) with the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][Tf2N]) in the presence and absence of water. Our results indicate that the addition of TBP or TBPO to a solution containing low concentrations of water in [EMIM][Tf2N] disrupts existing water–water hydrogen bonding interactions as well as those between water and the imidazolium ring protons. Significant shifts in the 1H NMR signal for imidazolium ring protons upon addition of TBP or TBPO suggest that terminal PO oxygen atoms engage in hydrogen bonding interactions with these protons. Results from 2H NMR, 17O NMR and ATR-FTIR spectra indicate that TBP and TBPO engage in hydrogen bonding interactions with water in the ionic liquid. Our results show that addition of water and TBP or TBPO can have a significant influence on [EMIM][Tf2N] hydrogen bonding interactions, and thus potentially affect the physical and chemical properties of this ionic liquid.