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Determination of LFER Descriptors of 30 Cations of Ionic Liquids—Progress in Understanding Their Molecular Interaction Potentials
Author(s) -
Cho ChulWoong,
Jungnickel Christian,
Stolte Stefan,
Preiss Ulrich,
Arning Jürgen,
Ranke Johannes,
Krossing Ingo,
Thöming Jorg
Publication year - 2012
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201100872
Subject(s) - taft equation , chemistry , ionic liquid , polarizability , hydrogen bond , free energy relationship , molar refractivity , solvation , acetonitrile , alkyl , high performance liquid chromatography , chromatography , organic chemistry , molecule , quantitative structure–activity relationship , stereochemistry , substituent , reaction rate constant , kinetics , physics , quantum mechanics , catalysis
In order to understand molecular interaction potentials of 30 cations of ionic liquids (ILs), the well‐known linear free energy relationship concept (LFER) was applied. The LFER descriptors for the excess molar refractivity and the molar volume were calculated in silico and for hydrogen‐bonding acidity and basicity, and the polarizability/dipolarity of IL cations were experimentally determined through high performance liquid chromatography (HPLC) measurements. For the study, three different columns (RP‐select B, Cyan, and Diol) and buffered mobile phases, based on two organic solvents acetonitrile (ACN) and methanol (MeOH), were selectively combined to the HPLC separation systems RP‐select B‐ACN, RP‐select B‐MeOH, Cyan‐MeOH, Diol‐ACN, and Diol‐MeOH. By measuring the retention factors of 45 neutral calibration compounds and calculating LFER descriptors of three cations in the HPLC systems, the system parameters, including an ionic z coefficient, were determined. Conversely, the LFER descriptors of 30 ionic liquid cations were determined, based on the parameters of five systems and their retention factors in the HPLC systems. The results showed that the type of head group, alkyl chain length and further substituents of the cation have a significant influence on the dipolarity/polarizability and the hydrogen‐bonding acidity, and functionalized groups (hydroxyl, ether, and dimethylamino) lead to hydrogen‐bonding basicity of the cation. The characterization of cationic LFER descriptors opens up the chance for a more quantitative understanding of molecular interaction potentials and physicochemical properties of ILs.