Artificial anion selective ion channels with single-file multiple anion-recognition sites are rare. Here, we have designed, by hypothesis, a small molecule that self-organizes to form a barrel rosette ion channel in the lipid membrane environment. Being amphiphilic in nature, this molecule forms nanotubes through intermolecular hydrogen bond formation, while its hydrophobic counterpart is stabilized by hydrophobic interactions in the membrane. The anion selectivity of the channel was investigated by fluorescence-based vesicle assay and planar bilayer conductance measurements. The ion transport by a modified hopping mechanism was demonstrated by molecular dynamics simulation studies.

We have investigated the liquid phase of an ionic liquid (IL), methylammonium formate (MAF), through the first principles molecular dynamics simulations using van der Waals (vdW) corrected exchange and correlation functionals of the density functional theory. The simulations were carried out to obtain a comparative study of various properties of the MAF using two different generalized gradient approximation functionals (Becke− Lee−Yang−Parr (BLYP) and Perdew−Burke−Ernzerhof (PBE)) along with three types of dispersion corrections (D2, D3, and dispersion-corrected atom-centered one-electron potentials), and two values of the plane-wave cutoff (300 and 600 Ry). We have evaluated the effects of various electronic parameters in describing the hydrogen-bonded structure and dynamical properties of MAF by performing 10 sets of molecular dynamics simulations. Thermodynamic properties are found to be sensitive to the details of electronic structure calculations. Our results of PBE functionals with the semiempirical vdW method provide the best agreement with experimental density. The overall density predictions match the cohesive energy trends, and the calculations incorporating dispersion forces exhibit enhanced intermolecular interactions within the hydrogen-bonded IL framework. All of the vdW-corrected BLYP functionals, mainly the dispersion-corrected atom-centered one-electron potential (DCACP) method, illustrate a well-defined structure of liquid MAF. To look into the dynamical perspective of the hydrogen-bond descriptions, we elucidate two possible mechanistic pathways of the hydrogen-bond jump events between the counterions. The hydrogen-bond breaking and forming mechanism along with the collision dynamics can be best described by incorporating dispersion interactions alongside the exchange and correlation functionals within the Kohn−Sham scheme. The rattling dynamics of ions are observed for dispersion-corrected functionals. Hence, an accurate representation of the delicately balanced interactive forces within ionic liquids is a necessary step toward a better description of its thermophysical and structural properties along with the associated ionic dynamics.

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We examine the hydrogen bond jump mechanism in ionic liquid, ethyl ammonium nitrate (EAN), using classical molecular dynamics simulations. Hydrogen bond jump in EAN can occur through two different nondiffusive rotational jump mechanisms: N–H bond of ethyl ammonium can switch its hydrogen bond between two oxygen atoms of the same nitrate ion or it can break its hydrogen bond with the oxygen of a nitrate ion to form a new hydrogen bond with the oxygen atom of another nitrate ion. We observe the average magnitude of the jump angle of 30° in the first mechanism, whereas the jump angle for the second mechanism is 70°. The in-plane rotation of nitrate ion facilitates the H-bond switch in the first mechanism, whereas the rotation of the ammonium group of cation around the C–N bond facilitates the H-bond switch in the second mechanism. The jump angle observed in the second mechanism qualitatively agrees with experimentally observed large jump angle. We also investigate the effect of temperature on this nondiffusive rotational dynamics of ionic liquid to observe the changes in the jump angle and its distributions.

Solvation free energies of methylated nucleobases were calculated in pure and hydrated 1-ethyl-3-methylimidazolium acetate, [Emim][Ac], ionic liquid, and pure water using classical molecular dynamics simulations using multistate Bennett’s acceptance ratio method. The calculated solvation free energies in pure water were compared with the previous experimental and theoretical findings and found to be in agreement. We observe that the solvation free energy of methylated nucleobases is more in the pure ionic liquid compared to that in the pure water and on changing the mole fraction of water in the ionic liquid, the solvation free energy decreases gradually. Comparing the Coulombic and van der Waals contribution to the solvation free energy, electrostatic contribution is more compared to that of the latter for all nucleobases. To obtain the atomistic details and explain the solvation mechanism, we calculated radial distribution functions (RDFs), spatial distribution functions (SDFs), and stacking angle distribution of cations to the nucleobases. From RDFs and SDFs, we find that the acetate anions of the ionic liquid are forming strong hydrogen bonds with the amine hydrogen atoms of the nucleobases. These hydrogen bonds contribute to the major part of the Coulombic contribution to the solvation free energy. Stacking of cations to the nucleobases is primarily due to the van der Waals contribution to the solvation free energy.