Theoretical study of ionic liquids based on the cholinium cation. Ab initio simulations of their condensed phases

We have explored by means ofab initiomolecular dynamics the homologue series of 11 differentionic liquids based on the combination of the cholinium cation with deprotonated amino acidanions. We present a structural analysis of the liquid states of these compounds as revealed byaccurateab initiocomputations of the forces. We highlight the persistent structural motifs thatsee the ionic couple as the basic building block of the liquid whereby a strong hydrogen bondingnetwork substantially determines the short range structural behavior of the bulk state. Other minordocking features of the interaction network are also discovered and described. Special cases alongthe series such as Cysteine and Phenylalanine are discussed in the view of their peculiar propertiesdue to zwitterion formation and additional long-range structural organization