On the Formation of a Protic Ionic Liquid in Nature

Abstract

The practical utility of ionic liquids (ILs) makes the absence (heretofore) of reported examples from nature quite puzzling, given the facility with which nature produces many other types of exotic but utilitarian substances. In that vein, we report here the identification and characterization of a naturally occurring protic IL. It can be formed during confrontations between the ants S. invicta and N. fulva. After being sprayed with alkaloid-based S. invicta venom, N. fulva detoxifies by grooming with its own venom, formic acid. The mixture is a viscous liquid manifestly different from either of the constituents. Further, we find that the change results as a consequence of formic acid protonation of the N centers of the S. invicta venom alkaloids. The resulting mixed-cation ammonium formate milieu has properties consistent with its classification as a protic IL.

Brønsted acidity of bio-protic ionic liquids: the acidic scale of [AA]X amino acid ionic liquids

“…3 With the development of study, ILs are now considered not only as important alternative green media (solvents) and high efficiency catalysts, but as a new type of multifunctional materials for energy, industry, and medicine applications. 6 A distinct characteristic of PILs is their supposed Brønsted acidity. Most of them can be easily obtained by one-step protonation reactions without any by-product.…”

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

“…[23][24][25][26][27] Moreover,w hen other inorganic salts, such as Mg(NO 3 ) 2 ,C a(NO 3 ) 2 ,a nd Al(NO 3 ) 2 ,a re dissolved into PILs, the metal cations( Mg 2 + ,C a 2 + ,a nd Al 3 + )a re more likely to reside in polar domains. [14,15,72,100,101] This arrangement is also favoredb yL i + ,w hich is found close to the polar groups and is strongly associated with the nitrate ions. [43,47] Also in EAN, the lithium ion is knownt ob es olvated by af irst shell of nitrate ion, which screen it from the resto ft he liquid.…”

Widespread Chemical Detoxification of Alkaloid Venom by Formicine Ants

“…However, we do know alkaloids are a target of detoxification behavior. Formic acid protonates the fire ant venom piperidine alkaloids forming a protic ionic liquid with very different physical properties from its precursor (Chen et al 2014). Formic acid will likely do the same for structurally related but chemically diverse alkaloids of other Solenopsis and Monomorium ants (Jones et al 1982), thus creating the possibility that a wide variety of naturally occurring ionic liquids arise from interactions between these ants and formicines.…”

“…Although it is not yet demonstrated how formic acid alters the bioactivity of fire ant venom, formic acid protonates the nitrogen in fire ant venom alkaloids forming a protic ionic liquid with distinct physical properties (Chen et al 2014). Among changes to the venom including the denaturation of associated venom enzymes and an increase in viscosity, the formate salt of the alkaloid is more polar and less lipophilic, which may reduce the ability of the protonated alkaloid to penetrate the waxy cuticle or cell membranes (Meinwald 2014).…”