Host-Guest Complexes of Flavylium Cations and Cucurbit[7]uril: The Influence of Flavylium Substituents on the Structure and Stability of the Complex

Nuno Basílio, Vesselin Petrov, Fernando Pina

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

The host-guest complexes formed from six differently substituted flavylium cations and cucurbit[7]uril (CB7) have been characterized by UV/Vis absorption, fluorescence emission and 1H NMR spectroscopy. It was observed that all flavylium cations form 1:1 inclusion complexes with association constants that depend on the nature and position of the substituents. The results indicate that CB7 displays higher affinity for more hydrophobic flavylium compounds and for those bearing amino substituents. 1H NMR spectroscopy was used to elucidate the structure of the complexes. While for 7-hydroxyflavylium and 4-methyl-7-hydroxyflavylium the phenyl group (ring B) is included within the host's cavity leaving the benzopyrilium group (rings A and C) outside, in 4′,7-dihydroxyflavylium and 3′,4′,7-trihydroxyflavylium the macrocycle shuttles between rings A and B. For compounds with amino substituents it was found that CB7 is attracted towards these groups regardless of their position in ring A or B. In addition, it was observed that the dimethylamino group tends to be positioned near the carbonyl-decorated portal while the diethylamino motif prefers the hydrophobic cavity of CB7.

Original languageEnglish
Pages (from-to)1779-1785
Number of pages7
JournalCHEMPLUSCHEM
Volume80
Issue number12
DOIs
Publication statusPublished - 1 Dec 2015

Keywords

  • cucurbiturils
  • flavylium compounds
  • host-guest systems
  • molecular recognition
  • NMR spectroscopy

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