Triphilic ionic-liquid mixtures: fluorinated and non-fluorinated aprotic ionic-liquid mixtures

We present here the possibility of forming triphilic mixtures from alkyl- and fluoroalkylimidazolium ionic liquids, thus, macroscopically homogeneous mixtures for which instead of the often observed two domainspolar and nonpolarthree stable microphases are present: polar, lipophilic, and fluorous ones. The fluorinated side chains of the cations indeed self-associate and form domains that are segregated from those of the polar and alkyl domains. To enable miscibility, despite the generally preferred macroscopic separation between fluorous and alkyl moieties, the importance of strong hydrogen bonding is shown. As the long-range structure in the alkyl and fluoroalkyl domains is dependent on the composition of the liquid, we propose that the heterogeneous, triphilic structure can be easily tuned by the molar ratio of the components. We believe that further development may allow the design of switchable, smart liquids that change their properties in a predictable way according to their composition or even their environment

Probing Liquid-Ordered and Disordered Phases in Lipid Model Membranes: A Combined Theoretical and Spectroscopic Study of a Fluorescent Molecular Rotor

An integrated theoretical/experimental strategy has been applied to the study of environmental effects on the spectroscopic parameters of 4-(diphenylamino)phtalonitrile (DPAP), a fluorescent molecular rotor. The computational part starts from the development of an effective force field for the first excited electronic state of DPAP and proceeds through molecular dynamics simulations in solvents of different polarities toward the evaluation of Stokes shifts by quantum mechanics/molecular mechanics (QM/MM) approaches. The trends of the computed results closely parallel the available experimental results thus giving confidence to the interpretation of new experimental studies of the photophysics of DPAP in lipid bilayers. In this context, results show unambiguously that both flexible dihedral angles and global rotations are significantly retarded in a cholesterol/DPPC lipid matrix with respect to the DOPC matrix, thus confirming the sensitivity of DPAP to probe different environments and, therefore, its applicability as a probe for detecting different structures and levels of plasma membrane organization

Effect of alkyl chain length in protic ionic liquids: an AIMD perspective

In this study we have explored, by means of ab initio molecular dynamics, a subset of three different protic ionic liquids (ILs). We present both structural and dynamical information of the liquid state of these compounds as revealed by accurate ab initio computations of the interactions. Our analysis figures out the presence of a strong hydrogen bond network in the bulk state, that is more stable in those ILs characterised by a longer alkyl side chain. Indeed it becomes more long-lasting passing from ethyl ammonium to butyl ammonium, owing to the hydrophobic effects stemming from alkyl chain contacts. Furthermore, the relative free energy landscape of the cation-anion interaction exhibits a progressively deeper well as the side chain of the cation gets longer. The hydrogen bond interaction, as already mentioned in previous works, leads to loss of degeneracy of the asymmetric stretching vibrations of the nitrate anions. The resulting frequency splitting between the two normal modes is about 90 cm(-1)

X-RAY SCATTERING AND MOLECULAR DYNAMICS STUDY OF LIQUID 1-ALKYL-3-METHYLIMIDAZOLIUM-CHLORIDES

We report the results from a X-Ray scattering study of imidazolium-based ionic liquid containing the chloride anion. The systems studied were the series of 1-alkyl-3-methylimidazolium-chlorides ([Rmim][Cl]) with R = butyl, [bmim][Cl], R = hexyl, [hmim][Cl] and R= octyl, [omim][Cl]. The structure of these liquids was also investigated through molecular dynamics. Simulations were performed using OPLS-AA force field in NVT ensemble. The measured diffraction patterns are compared with the theoretical spectra obtained from model geometries derived from molecular dynamics trajectories. This comparison provides both a tool for interpretation of experiments and a way to validate the computational protocol. Using our model, we also determined the local structure of the liquid through radial distribution functions. The mutual positions of the cation-anion units as well as the conformation of the alkyl chain of the cation were investigated in the series. The local structure and the conformation of the alkyl chain of the cation for this series of ionic liquids were compared with the results of the series 1-alkyl-3-methylimidazolium-hexafluorophosphates ([Rmim][PF6]). The comparison shades light on the role played by the nature of the anion and by its dimension