Abstract (EN):
By employing 1H NMR spectroscopy and molecular simulations, we provide an explanation for recent
observations that the aqueous solubilities of ionic liquids exhibit salting-out to salting-in regimes upon addition
of distinct inorganic salt ions. Using a typical ionic liquid [1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)
imide], we observed the existence of preferential specific interactions between the low electrical
charge density (“apolar moiety”) parts of the ionic liquid cation and the inorganic salts. These a priori
unexpected interactions become increasingly favorable as one moves from salting-out to salting-in effects.
More specifically, this interpretation is validated by distinct aqueous solution 1H NMR data shifts in the ionic
liquid cation upon inorganic salt addition. These shifts, which are well noted in the terminal and preterminal
hydrogens of the alkyl chain appended to the imidazolium ring, correlate quantitatively with solubility data,
both for cases where the nature of inorganic salt is changed, at constant concentration, and for those where
the concentration of a given inorganic salt is varied. Molecular simulations have also been performed permitting
us to garner a broader picture of the underlying mechanism and structure of this complex solvation phenomenon.
These findings can now be profitably used to anticipate solution behavior upon inorganic salt addition well
beyond the specificity of the ionic liquid solutions, i.e., for a diversity of distinct solutes differing in chemical
nature.
Idioma:
Inglês
Tipo (Avaliação Docente):
Científica
Contacto:
jcoutinho@ua.pt