Faculty of Chemistry and Chemical Technology, University of Ljubljana, SI-1000 Ljubljana, Slovenia.
Phys Chem Chem Phys. 2011 Oct 21;13(39):17588-98. doi: 10.1039/c1cp21371g. Epub 2011 Sep 5.
Ion association of the ionic liquid [bmim][Cl] in acetonitrile and in water was studied by dielectric spectroscopy for salt concentrations c ≤ 1.3 M at 298.15 K and by measurement of molar electrical conductivities, Λ, of dilute solutions (c ≤ 0.006 M) in the temperature range 273.15 ≲ T/K ≤ 313.15. Whilst acetonitrile solutions of [bmim][Cl] exhibit moderate ion pairing, with an association constant of K°(A) ≈ 60 M(-1) and increasing with temperature, [bmim][Cl] is only weakly associated in water (K°(A) ≈ 6 M(-1)) and ion pairing decreases with rising temperature. Only contact ion pairs were detected in both solvents. Standard-state enthalpy, entropy and heat capacity changes of ion association were derived, as well as the activation enthalpy of charge transport and the limiting conductivity of the cation, λ(∞) (bmim). These data, in conjunction with effective solvation numbers obtained from the dielectric spectra, suggest that the solvation of bmim is much weaker in water than in acetonitrile.
在 298.15 K 下，通过介电光谱法研究了离子液体 [bmim][Cl] 在乙腈和水中的离子缔合，盐浓度 c ≤ 1.3 M；通过测量稀溶液（c ≤ 0.006 M）在 273.15 ≲ T/K ≤ 313.15 温度范围内的摩尔电导率 Λ。虽然 [bmim][Cl] 在乙腈溶液中表现出中等程度的离子对缔合，缔合常数 K°(A) ≈ 60 M(-1) 并随温度升高而增加，但 [bmim][Cl] 在水中仅弱缔合（K°(A) ≈ 6 M(-1))，且随着温度的升高，离子对缔合程度降低。在两种溶剂中都只检测到接触离子对。推导了离子缔合的标准态焓、熵和热容变化，以及电荷传输的活化焓和阳离子的极限电导率 λ(∞) (bmim)。这些数据，结合介电光谱获得的有效溶剂化数，表明 bmim 在水中的溶剂化作用比在乙腈中弱得多。
