abstract
The interaction of imidazolium-based ionic liquids with alpha- and beta-cyclodextrins was investigated by electrospray ionization mass spectrometry with variable collision induced dissociation energy and quantum chemical gas-phase calculations. The center-of-mass energy at which 50 % of a precursor ion decomposes (E-cm,E-1/2) was determined for the isolated [cyclodextrin + cation](+) or [cyclodextrin + anion](-) adduct ions of imidazolium-based ionic liquids with different alkyl chain lengths combined with a large set of anions, such as chloride, bromide, bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, methanesulfonate, dicyanamide, and hydrogensulfate. Moreover, both symmetric and asymmetric imidazolium cationic cores were evaluated. The relative interaction energies in the adduct ions were interpreted in terms of the influence of cation/anion structures and their inherent properties, such as hydrophobicity and hydrogen bond accepting ability, in the complexation process with the cyclodextrins. The trends observed in the mass spectral data together with quantum-chemical calculations suggest that in the gas phase, cations and anions will preferentially interact with the lower or upper rim of the cyclodextrin, respectively, as opposed to what has been reported in condensed phase where the formation of an inclusion complex between ionic liquid and cyclodextrin is assumed.
keywords
ELECTROSPRAY MASS-SPECTROMETRY; HOST-GUEST COMPLEXATION; BETA-CYCLODEXTRIN; SUPRAMOLECULAR CHEMISTRY; MOLECULAR RECOGNITION; ALPHA-CYCLODEXTRIN; AQUEOUS-SOLUTIONS; NONCOVALENT INTERACTIONS; INORGANIC ANIONS; WATER
subject category
Biochemistry & Molecular Biology; Chemistry; Spectroscopy
authors
Fernandes, AM; Schroder, B; Barata, T; Freire, MG; Coutinho, JAP
our authors
Bernd Schroder
Post-doc Fellowship
Mara Guadalupe Freire Martins
Coordinating ResearcherGroups
G4 - Renewable Materials and Circular Economy
G5 - Biomimetic, Biological and Living Materials
Projects
acknowledgements
Thanks are due to Fundacao para a Ciencia e a Tecnologia (FCT, Portugal) and European Union, QREN, FEDER, and COMPETE for funding the QOPNA research unit (project PEst-C/QUI/UI0062/2011) and CICECO (Pest-C/CTM/LA0011/2011). B.S. acknowledges the award of a FCT post-doctoral grant (SFRH/BPD/38637/2007) and the FCT project (PTDC/AAC-AMB/121161/2010). T.B. acknowledges a FCT BII grant, M.G.F. acknowledges a FCT postdoctoral grant SFRH/BPD/41781/2007.