Inclusion complex formation of ionic liquids and other cationic organic compounds with cucurbit[7]uril studied by 4',6-diamidino-2-phenylindole fluorescent probe

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The encapsulation of 4',6-diamidino-2-phenylindole (DAPI) in the cucurbit[7]uril (CB7) cavity was studied by absorption, fluorescence, and NMR spectroscopic methods in aqueous solution. The profound change in the fluorescence characteristics was attributed to the formation of a very stable 1:1 inclusion complex. Three independent methods provided (1.1 ±0.1) x 107 M-1 value for the binding constant. DAPI proved to be an excellent fluorescent probe for the investigation of the competitive binding of ionic liquids, surfactants, and biologically important compounds to CB7. The equilibrium constant of l-alkyl-3-methylimidazolium inclusion was found to go through a maximum as the aliphatic chain length was increased, reaching the highest value for the hexyl derivative. The variation of the anion had a small effect. Among cationic surfactants containing a dodecyl tail, the stability of CB7 complex diminished with the growing hydrophobicity of the head group.

Original languageEnglish
Pages (from-to)1645-1651
Number of pages7
JournalJournal of Physical Chemistry B
Issue number6
Publication statusPublished - Feb 12 2009


ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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