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Séminaire LCP de Enrico Bodo (La Sapienza - Italie)


Séminaire LCP de Enrico Bodo (La Sapienza - Italie)

VENDREDI 17 NOVEMBRE 2017 à 14 h 00 en salle Magat, bât. 349 “Proton Mobility in Protic Ionic Liquids : testing new materials for electrochemistry through accurate ab-initio computations” par Enrico Bodo (Université de Rome La Sapienza - Italie)

Résumé

Ionic liquids (ILs) are salts made by bulky, sterically mismatched molecular ions that possess a low melting point because the electrostatic interactions are weakened by charge delocalization and lattice formation frustrated by geometric effects. In contrast to traditional organic solvents, ILs possess negligible flammability and volatility and represent a new class of "green" solvents that are inherently safer than conventional solvents. A Protic Ionic Liquid (PIL) is formed through an acid base reaction. When the difference of pKa between the acid and the conjugate acid of the base is large (>10 pKa units) the ensuing liquid is completely ionized. In this case, the acidic proton is transferred quantitatively from the acid to the base during the synthesis reaction and turns out to be strongly bound to the latter. Subsequent proton transfer is therefore not possible. Conduction in these liquids is therefore due to ion drift (Walden mechanism) and inversely proportional to the liquid viscosity. In order to have a larger conductivity one has to find a way to promote the formation of different charge carriers. One possibility is to have proton transfer from one molecular ion to another. Compounds where amino acids in their deprotonated (anionic) form are combined with inorganic cations such as [Ch][Asp] and [Ch][Cys] might have these features. The former has a weak acid terminal, while the latter has a weak basic proton attached to the sulphur atom. We will show evidences of a non-ordinary behavior of these two materials that have been obtained by carefully validated ab-initio and classical molecular dynamics simulations [1,2].

[1] Marco Campetella, Maria Montagna, Lorenzo Gontrani, Eleonora Scarpellini and Enrico Bodo, Unexpected Proton Mobility in the bulk phase of Cholinium-based Ionic Liquids. New Insights from Theoreti- cal Calculations
Phys. Chem. Chem. Phys., 19, 11869 - 11880, (2017)
[2] M. Campetella, E. Bodo*, M. Montagna, S. De Santis and L. Gontrani Theoretical study of ionic liquids based on the cholinium cation. Ab initio simulations of their condensed phases, J. Chem. Phys. 144, 104504 (2016)

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