Solvation of Inorganic Nitrate Salts in Protic Ionic Liquids

Abstract

The bulk nanostructure of several inorganic salt solutions in protic ionic liquids is elucidated using neutron diffraction and empirical potential structure refinement (EPSR) modelling. The protic ionic liquids studied are ethylammonium nitrate (EAN) and ethanolammonium nitrate (EtAN), which are mixed with either LiNO 3 , Mg(NO 3 ) 2 , Ca(NO 3 ) 2 , or Al(NO 3 ) 3 , at 1:10 or 1:30 solute:solvent mol:mol ratios. The models show inorganic metal ions are solvated within the polar domains of the nanostructure, and can induce significant differences in bulk solvent nanostructure from that of the pure ionic liquids. For EtAN, the uncharged groups aggregate and form an apolar domain in spite of the cation's reduced amphiphilicity because the TRANS rotamer is favoured when an inorganic salt is added.

Mapping the Free Energy of Lithium Solvation in the Protic Ionic Liquid Ethylammonuim Nitrate: A Metadynamics Study

“…Therefore, there is a clear competition between the lithium coordination with 3, and 4 nitrates respectively. It was previously reported [47] that every Li + cation is solvated by approximately four nitrates, and this is in line with our simulations.…”

“…Moreover, when other inorganic salts, like Mg(NO 3 ) 2 , Ca(NO 3 ) 2 , and Al(NO 3 ) 2, are dissolved into PILs, the metal cations (Mg 2+ , Ca 2+ , and Al 3+ ) are more likely to reside in polar domains [14,15,72,100,101] . This arrangement is also favored by the Li + , which is found close to the polar groups and is strongly associated with the nitrate ions [43,47] . Also in EAN, the Li ion is known to be solvated by a first shell of nitrates, which screen it from the rest of the liquid.…”

Simulations of room temperature ionic liquids: from polarizable to coarse-grained force fields

“…This important finding is now commonly used to interpret the solvation properties of RTILs towards many species, such as nitrate ions 52,53 or acidic (SO 2 , CO 2 ) gases. 54,55 It was also ex- Although the CL&P (and related) force fields have led to a deep understanding of the structure of RTILs, they generally fail to predict the transport properties.…”

Does Addition of an Electrolyte Influence the Rotational Diffusion of Nondipolar Solutes in a Protic Ionic Liquid?

“…The presence of Li + and extra NO 3 − ions in the polar domain disrupts packing in the nonpolar domain and produces a weak structure-breaking effect. 12 It has also been inferred that Li + ions in the polar domains progressively erode the hydrogen bonding network of the protic ionic liquid and decrease the extent of hydrogen bonding of the mixtures. As a consequence, orientational disorder is induced in the polar domains and this effect is more pronounced in the case of protic ionic liquids with longer alkyl chains where a lower degree of hydrogen bonding prevails.…”