Inherently Chiral" Ionic Liquids:New Media for Chiral Voltammetry

In "inherently chiral" molecular materials the coincidence of the stereogenic element with the molecular portion responsible for their specific properties was shown to result in outstanding enantioselectivity as electrode surfaces.We successfully experimented this concept in designing chiral organic semiconductors employed as highly stereoselective electrode surfaces. In this work inherently chiral ionic liquids ICILs 1 have been prepared starting from 3,3'-bicollidine, which can be synthesized from inexpensive reagents, separated into stable enantiomers by crystallization of the diastereeomeric salts with D- and L-O,O-dibenzoyltartaric acids, and converted into long-chain dialkyl salts with melting points below room T. All the steps of the sequence have been scaled up to several tenths of grams. Both the new inherently chiral ILs and shorter family terms (solid at room T), employed as low concentration additives in commercial achiral ionic liquids, afford outstanding enantiodiscrimination of the oxidation peaks of structurally different chiral probes (L- and D-DOPA and their methyl esters, (R)- and (S)-N,N-dimethyl-1-ferrocenylethylamines and the antipodes of a chiral oligothiophene) on achiral electrodes, comparable to that obtained on inherently chiral electrodes and regularly increasing with additive concentration.