Molecular Solvent Effects Research Articles

Molecular solvent effect on the acidity constant of protic ionic liquids

In this work how the microscopic properties of a molecular solvent affect the chemical environment of the protic ionic liquids (PILs) was analyzed. Using Reichardt’s dye as indicator of acidity, new acidity constant values for eight PILs (pKaPILs) were determined by spectrophotometric titration. Modifying the character hydrogen bonding donor of the molecular solvent it is possible to handle the PIL acid strength. Thus, we can turn basic PILs into acidic ones thereby the molecular solvent could be used as ‘additive’ for PILs, which allowed us to tune PILs design.

Behavior of Nitroxide Biradicals with Acetylene Bridges in Organic Solvents and Ionic Liquids

Intramolecular electron spin exchange (IESE) in two nitroxide biradicals, R6–C≡C–C≡C–R6 (1) and R6–C≡C–p-C6H4–C≡C–R6 (2), is studied as a function of temperature and solvent properties. The effect of molecular solvents and ionic liquids (ILs, [1-methyl-3-butylimidazolium]+[PF6]−, bmimPF6, and [1-methyl-3-octylimidazolium]+[BF4]−, omimBF4) on the IESE in magnetically diluted solutions is investigated. Changes in electron paramagnetic resonance spectra are analyzed and the thermodynamic parameters of these changes are calculated. Geometry optimization and D-tensor calculations of biradicals 1 and 2 were carried out on the DFT/UB3LYP/cc-pVdz and DFT/ROPBE/N07D levels of theory. The probable differences in biradical behavior are discussed.

The effect of molecular solvents on the viscosity, conductivity and ionicity of mixtures containing chloride anion-based ionic liquid

Chloride anion-based ionic liquids (ILs) have unique importance among various ILs. Nevertheless, they are usually very viscous, and the study on their mixtures with molecular solvent is important for their practical application. In this work, the viscosities and conductivities of the binary mixtures of 1-butyl-3-methylimidazolium chloride and several protic/aprotic solvents were measured, and the underlying information about intermolecular interaction and microscopic structure was discussed. The result showed that the molecular solvents which have relatively high dielectric constant and hydrogen-bond acidity will be more efficient in promoting the dissociation of chloride anion-based ILs and improving the transport properties of corresponding applications.

Fundamental aspects of electrostatic interactions and charge renormalization in electrolyte systems

The consistent inclusion of ion-ion correlations and molecular solvent effects in electrolyte theory can be expressed in a physical formalism, where the particles acquire a renormalized charge density and where they interact electrostatically via a generalized screened Coulomb potential. The latter usually decays for large distances r like a Yukawa function exp(-κr)/r, where 1/κ is the decay length (normally different from the Debye length), but, for smaller r, the screened Coulomb potential is a more complicated function. The resulting electrostatic theory, “Yukawa electrostatics”, differs in many important aspects from ordinary (unscreened) Coulomb electrostatics. In the present paper, we give illustrations and explanations of some important differences between Coulomb and Yukawa electrostatics. The effective “Yukawa charge” of a particle differs from the ordinary Coulombic charge. Furthermore, contributions from multipoles of all orders contribute, in general, to the leading asymptotic term in the potential for large r, which decays like exp(-κr)/r. Thus, the electrostatic potential from, for example, an electroneutral molecule with an internal charge distribution has generally the same range as the potential from an ion. Some implications of these facts are pointed out. The presentation is based on exact statistical mechanical analysis where all particles are treated on the same fundamental level, but the main focus lies on physical consequences and interpretations of the theory.

Forces between like-charged walls in electrolyte solution: Molecular solvent effects at the McMillan–Mayer level

The force between two like-charged walls immersed in electrolyte solution is obtained for models that include solvent effects at the McMillan–Mayer (MM) level. In these models the solvent is not represented by discrete particles but exerts its influence through solvent-averaged ion–ion potentials of mean force which serve as effective potentials. This simplification allows the numerical solution of accurate anisotropic integral equation theories, and the anisotropic hypernetted-chain (AHNC) approximation is used in the present calculations. It is shown that the MM results may differ significantly from those of the primitive model (PM) which treats the solvent as a dielectric continuum. Most interestingly, we find that at the MM level the force between like-charged walls at small separations and with realistic surface charges can be attractive for monovalent counterions. This attraction is due to solvent effects on the effective counterion–counterion interaction and not to the correlated charge fluctuations that give rise to the attractions found for divalent counterions in the PM case. The possible relevance of our observations in the interpretation of experimental force measurements is briefly discussed.

Path integral's formulation of the molecular solvent effects

With the formalism of the path-integral into molecular-orbital theory, we introduce the quaturn fluctuation into the molecular ground state. As a consequence, a non-linear formulation of the molecular orbitals is obtained. Then, we connect the non-linear term of the effective Hamiltonian with the solvent effects of the environment surrounding the molecular system, and explain this mechanism.