Empirical Parameters for Solvent Acidity, Basicity, Dipolarity, and Polarizability of the Ionic Liquids [BMIM][BF₄] and [BMIM][PF₆]

Abstract

The empirical solvent scales for polarizability (SP), dipolarity (SdP), acidity (SA), and basicity (SB) have been successfully used to interpret the solvatochromism of compounds dissolved in organic solvents and their solvent mixtures. Providing that the published solvatochromic parameters for the ionic liquids 1-(1-butyl)-3-methylimidazolium tetrafluoroborate, [BMIM][BF4] and 1-(1-butyl)-3-methylimidazolium hexafluorophosphate, [BMIM][PF6], are excessively widespread, their SP, SdP, SA, and SB values are measured herein at temperatures from 293 to 353 K. Four key points are emphasized herein: (i) the origin of the solvatochromic solvent scales--the gas phase, that is the absence of any medium perturbation--; (ii) the separation of the polarizability and dipolarity effects; (iii) the simplification of the probing process in order to obtain the solvatochromic parameters; and (iv) the SP, SdP, SA, and SB solvent scales can probe the polarizability, dipolarity, acidity, and basicity of ionic liquids as well as of organic solvents and water-organic solvent mixtures. From the multiparameter approach using the four pure solvent scales one can draw the conclusion that (a) the solvent influence of [BMIM][BF4] parallels that of formamide at 293 K, both of them miscible with water; (b) [BMIM][PF6] shows a set of solvatochromic parameters similar to that of chloroacetonitrile, both of them water insoluble; and (c) that the corresponding solvent acidity and basicity of the ionic liquids can be explained to a great extent from the cation species by comparing the empirical parameters of [BMIM](+) with those of the solvent 1-methylimidazole. The insolubility of [BMIM][PF6] in water as compared to [BMIM][BF4] is tentatively connected to some extent to the larger molar volume of the anion [PF6](-), and to the difference in basicity of [PF6](-) and [BF4](-).

Photophysical properties and fluorosolvatochromism of D–π–A thiophene based derivatives

“…Catalán 62,63 has modied Kamlet-Ta relationship to be four parametric equation by splitting Kamlet-Ta dipolarity/ polarizability parameter (p*), into solvent polarizability (SP) and dipolarity (SdP) according to the following equation:…”

Properties of ionic liquid mixtures of [NH2e‐mim][BF4] and [bmim][BF4] as absorbents for CO2 capture

“…. Previous studies reported the densities of [NH 2 e‐mim][BF 4 ] and [bmim][BF 4 ] at 298 K to be 1420 kg·m −3 and 1117 kg·m −3 , respectively. As shown in Fig.…”

The Role of Hydrogen Bonding in Paracetamol–Solvent and Paracetamol–Hydrogel Matrix Interactions

“…and the position of the long-wavelength absorption (ν a ) and fluorescence (ν f ) maxima of PAR, ACT, and NEA. One the other hand, Kamlet and Taft [43,44] and also Catalán [45,46] developed multiparameter relationship for the description of the solvent effects (specific (aciditybasicity) and non-specific (polarity/polarizability)) on the luminescent characteristics (absorption and emission spectra, quantum yield, fluorescence lifetime etc.). In the present study, the Catalán model was chosen, because it allows to more detailed description, i.e., solvent polarity parameter has been separated by Catalán and co-workers into two independent parameters: solvent polarizability and dipolarity.…”

“…where SP and SdP parameters describe non-specific contributions regarding solvent polarizability and solvent dipolarity, respectively. The SA and SB parameters describe specific contributions regarding solvent's hydrogen bond donor strength and hydrogen bond acceptor strength, respectively [45,46]. In Equation ( 2), the relative contribution of the each solvent parameter (SP, SdP, SA, SB) to spectroscopic property (x) can be described by the regression coefficients: s SP , s SdP , a SA , b SB .…”