EDXD experiments in liquid phase - ionic liquids and molecular liquids
EDXD experiments on room temperature molten salts (ionic liquids) made up of different anions and cations are carried out.
The growing awareness of the pressing need for greener, more sustainable technologies has attracted attention regarding the use of alternative reaction media that circumvent the matters associated with traditional volatile organic solvents. Ionic liquids are simple liquids composed entirely of ions. They are generally salts of organic cations e.g. tetraalkylammonium, alkylpyridinium, 1,3-dialkylimidazolium, tetraalkylphosphonium and inorganic anions. Room temperature ionic liquids (RTIL) exhibit certain properties that make them attractive media for performing green catalytic reactions. They have essentially no vapour pressure and are thermally robust with liquid range of e. g. 300°C. Polarity and hydrophilicity can be tuned by a suitable combination of cation and anion, which has earned them the award ‘designer solvents’. Ionic liquids have been extensively studied in the last few years as media for organic
synthesis and catalysis. The major goal of the project is to analyze thoroughly the structures of pure ionic liquids and the interaction of the liquid with solutes, using a technique (energy dispersive X-ray diffraction) which has proved to be an excellent tool to study pure liquids and solutions in detail. It can give a picture (more or less "fine-grained" depending on the particular system and other physical observables, like temperature) of the spatial arrangement of the particles and the mutual interactions between them. The structure functions/radial distribution functions obtained from EDXD measurements are interpreted with statistical models (molecular dynamics simulations) and "static" quantochemical models.
Since last year, the research has been focussed on a new type of ionic liquids, composed of choline (cation) and aminoacid/carboxylic acid (anion). These systems are composed of bio-compatible ions, are almost atoxic and can be obtained from renewable sources. In choline-acid moltens salts very strong hydrogen bond interactions are present, and the simulation with classical molecular dynamics methods is rather inaccurate and require ri-parametrized force fields (e. g. with scaled charges, explicit polarization, etc). For this reason, I am currently carrying out ab initio molecular dynamics (DFT).