Effect of host-guest complex formation on the fluorescence of 6-methoxy-1-methyl-quinolinium cation with 4-sulfonatocalix[4]arene: Utilization as a fluorescent probe for the study of difenzoquat binding

József G. Harangozó, Zsombor Miskolczy, László Biczók, Veronique Wintgens, Cédric Lorthioir

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The complexation of the highly fluorescent 6-methoxy-1-methyl-quinolinium (C1MQ) and the widely used herbicide, difenzoquat (DFQ), with 4-sulfonatocalix[4]arene (SCX4) macrocycle was studied by isothermal titration calorimetry, fluorescence and NMR spectroscopy in aqueous solutions at 298 K. Both guests produced 1:1 complexes with SCX4, but the binding affinity of C1MQ was more than one order of magnitude larger than that of DFQ in neutral medium. The higher stability of C1MQ-SCX4 complex originated from the significant enthalpy gain upon its formation. The encapsulation of C1MQ in SCX4 in the ground state resulted in an efficient fluorescence quenching due to electron transfer from the host to the excited guest. The marked difference in the fluorescence quantum yields for free and bound C1MQ was used to detect the competitive complexation of DFQ in SCX4.

Original languageEnglish
Pages (from-to)377-384
Number of pages8
JournalJournal of Inclusion Phenomena and Macrocyclic Chemistry
Issue number3-4
Publication statusPublished - Apr 1 2015



  • Calorimetry
  • Competitive binding
  • Fluorescence quenching
  • Host-guest complex
  • Thermodynamics

ASJC Scopus subject areas

  • Food Science
  • Chemistry(all)
  • Condensed Matter Physics

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