title: Flavylium network of chemical reactions in confined media: modulation of 3',4',7-trihydroxyflavilium reactions by host-guest interactions with cucurbit[7]uril.
abstract: In moderately acidic aqueous solutions, flavylium compounds undergo a pH-, and in some cases, light-dependent array of reversible chemical reactions. This network can be described as a single acid-base reaction involving a flavylium cation (acidic form) and a mixture of basic forms (quinoidal base, hemiketal and cis and trans chalcones). The apparent pK'a of the system and the relative mole fractions of the basic forms can be modulated by the interaction with cucurbit[7]uril. The system is studied by using (1) H NMR spectroscopy, UV/Vis spectroscopy, flash photolysis, and steady-state irradiation. Of all the network species, the flavylium cation possesses the highest affinity for cucurbit[7]uril. The rate of interconversion between flavylium cation and the basic species (where trans-chalcone is dominant) is approximately nine times lower inside the cucurbit[7]uril.
authors.affiliation: REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Monte de Caparica (Portugal).
authors.forename: Nuno
authors.initials: N
authors.lastname: Basílio
authors.forename: Fernando
authors.initials: F
authors.lastname: Pina
mesh_terms: D002412:Cations / Q000737:chemistry; D055598:Chemical Phenomena; D005419:Flavonoids / Q000737:chemistry*; D047028:Macrocyclic Compounds / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D010782:Photolysis; D014466:Ultraviolet Rays; D000099246:Cucurbit(n)urils
chemical_list: D002412:Cations; D005419:Flavonoids; D047028:Macrocyclic Compounds; D000099246:Cucurbit(n)urils
keywords: cucurbiturils; flavylium ions; host-guest systems; phytochemistry; uv/vis spectroscopy