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Vendilo A.,Fine Chemicals Research Center | Popov K.,Fine Chemicals Research Center | Lajunen M.,University of Oulu | Chistov V.,Fine Chemicals Research Center | And 4 more authors.
Polyhedron | Year: 2014

Thermodynamic data for cesium complexes formation with 18-crown-6 (18C6, L) in five hydrophobic room temperature ionic liquids (RTIL): trioctylmethylammonium salicylate ([TOMA][Sal]), tetrahexylammonium dihexylsulfosuccinate ([THA][DHSS]), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([BMIM][N(Tf)2]), 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([HMIM][N(Tf)2]) as well as with 12-crown-4 (12C4, L) and 15-crown-5 (15C5, L) in [BMIM][N(Tf)2] are measured with NMR 133Cs technique at 27-50 °C. Only [Cs(18C6)]+ complexes are found for [TOMA][Sal], [THA][DHSS], [BMIM][PF6], while in [BMIM][N(Tf) 2] and [HMIM][N(Tf)2] both [Cs(18C6)]+ and [Cs(18C6)2]+ species are formed. For 12C4 and 15C5 only [CsL]+ species are registered in [BMIM][N(Tf)2]. For [BMIM][N(Tf)2] the log K1 values are steadily increasing: 12C4 < 15C5 < 18C6. A comparative study of [Cs(18C6)]+ stability in RTILs is estimated to be in the range between water and acetonitrile with constants increasing in the order [THA][DHSS] < [TOMA][Sal] < [BMIM][PF6] < [BMIM][N(Tf)2] < [HMIM][N(Tf)2]. It is demonstrated that unlike hydrophilic RTIL the entropy change with an exception of [BMIM][PF6], promotes complex formation while the corresponding enthalpy change is either positive or gives rather small contribution to the complex stability. © 2014 Elsevier Ltd. All rights reserved.

Popov K.I.,Fine Chemicals Research Center | Vendilo A.G.,Fine Chemicals Research Center | Chistov V.,Fine Chemicals Research Center | Ronkkomaki H.,Finnish Institute of Occupational Health | And 3 more authors.
Polyhedron | Year: 2013

Thermodynamic data for lithium complexes formation with 15-crown-5 (15C5, L) and 18-crown-6 (18C6, L) in a hydrophobic room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulphonyl]imide ([BMIM][N(Tf)2]) are measured with NMR 7Li technique at 27-57 °C. For 15C5 and 18C6 only LiL+ complexes are found. The stability of lithium complexes in RTIL is estimated to be in the range between water and acetonitrile. The following values for logK(Li + L) and ΔHo(Li + L) at 25 °C are determined: 1.66 (0.03), ∼0 kJ/mol for 15C5 and 2.0 (0.1), -17.0 (0.5) kJ/mol for 18C6, respectively. Unlike the situation with molecular solvents the lithium complex with 15C5 in [BMIM][N(Tf)2] is entropy stabilized. The polarity of [BMIM][N(Tf)2] fits well the existing empirical solvent polarity scale for molecular solvents characterizing the polarity of this RTIL as rather normal instead of "superpolar". © 2013 Elsevier Ltd. All rights reserved.

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