| Room temperature ionic liquids （RTILs）, which have received a great deal ofattention due to their unique properties such as low vapor pressure, high thermalstability, wide electrochemical windows, and have a wide variety of potentialapplications in biochemistry, pharmaceutical chemistry, organic synthesis,separation, electrochemical, catalytic. RTILs considered as an important direction ofthe development of green chemistry and have become a very active issue of frontiersof science. In recent years, RTILs have inter to a new stage and direction of thedevelopment of more greener and more functional. Functionalized ionic liquids havea wide applications such as fuel cells, surface active agent, organic reaction media.While protic ionic liquids （PILs） are today emerging as important materials with anamazing diversity in properties and applications, not much is known about thedetailed interaction mode and the proton transfer mechanism.The amino acid ionic liquids [HPro]+[Sac]-and [HProC1]+[Sac]-wassystematically studied by DFT/B3LYP and MP2methods with6-311+G（d,p） basisset. The stable geometries and interaction modes of the cation, anion, ionic pair,neutral pair, as well as the dimmer [HPro]2+[Sac]2-and [HProC1]2+[Sac]2-wereobtained and characterized. In the single [HPro]+[Sac]-and [HProC1]+[Sac]-units,proton transfer from cation to anion can be observed and testified by the TS and IRCcalculations. The lower energy barriers indicated that there exists the dynamicbalance between the ionic pairs and neutral pairs. The interaction intensity betweenthe fragments will significantly be weakened after H-transfer reaction. In the dimmer,proton transfer does not occur.In many cases these calculations have only study on a single ion or ion pair thatis often ignored Cooperativity in ionic liquids. So we using the DFT/B3LYP at6-311++G**level obtained the stable geometries of [HPro]2+[NO3]2-and[HProC1]2+[NO3]2-. By the computations of the total interaction binding energy forthe dimer [HPro]2+[NO3]2-and [HProC1]2+[NO3]2-and the AIM analysis was alsoperformed to analyze the interactions between the various fragments in the twoion-pairs coexisting system. We found that there is not occur proton transfer in thedimer and the structures of ion-pair are all ionic. This result will enrich theinvestigations that the proline cation based amino acid ionic liquid whether occurproton transfer. The components are stabilized by completely ionic-ionic interactionin [HProC1]2+[Sac]2-, and by jointly ionic-ionic and neutral-zwitterionic interactionsin [HPro]2+[Sac]2-. The proton transfer, the existence of zwitterion, and theesterification may play important roles in the physicochemical property change ofILs, which have been discussed. The H-bond chemical nature in the single ion-pairand dimmer were analyzed by the theory of atoms in molecules AIM.Using of the molecular dynamics （MD） simulation description the[ProC1]+[NO3]-in the supplementary AMBER99force filed ues the Tinker pack.Obtained the density, Ï,1.356g/cm3at300K and1.341g/cm3at330K,respectively. And compare with the density of conventional ionic liquid. In this work, we implement with the TINKER package obtained the molar evaporation enthalpy,isobaric heat content, radial distribution function, and so on. In the liquid phase,[HproC1]+[NO3]-ILs is stabilized by [HProC1]+and [NO3]-ion pairs, that may beused as a good electrolyte. |
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