title: Multistate/multifunctional behaviour of 4'-hydroxy-6-nitroflavylium: a write-lock/read/unlock/enable-erase/erase cycle driven by light and pH stimulation.
abstract: We have investigated the network of reactions observed for the photochromic 4'-hydroxy-6-nitroflavylium compound in aqueous solutions upon pH changes (including pH jump and stopped flow experiments) and light excitation. The changes observed in the NMR and UV/Vis spectra allowed identification of ten different forms in which this compound can be transformed depending on the experimental conditions. Equilibrium and kinetic constants have been determined. Compared with other members of the flavylium family, 4'-hydroxy-6-nitroflavylium is characterized by a large cis-->trans isomerization barrier, and a very efficient hydration reaction. These peculiar features allow writing, reading, storing and erasing photonic information on 4'-hydroxy-6-nitroflavylium by a novel cyclic process that involves the following steps: write-lock/read/unlock/enable-erase/erase.
authors.affiliation: Departamento de Química, Centro de Química-Fina e Biotecnologia-REQUIMTE, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Monte de Caparica, Portugal.
authors.forename: Margarida C
authors.initials: MC
authors.lastname: Moncada
authors.forename: A Jorge
authors.initials: AJ
authors.lastname: Parola
authors.forename: Carlos
authors.initials: C
authors.lastname: Lodeiro
authors.forename: Fernando
authors.initials: F
authors.lastname: Pina
authors.forename: Mauro
authors.initials: M
authors.lastname: Maestri
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Balzani
mesh_terms: D000098:Acetophenones / Q000737:chemistry* / Q000528:radiation effects*; D000475:Alkenes / Q000737:chemistry* / Q000528:radiation effects*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008027:Light; D015394:Molecular Structure; D009574:Nitro Compounds / Q000737:chemistry* / Q000528:radiation effects*; D010084:Oxidation-Reduction; D010777:Photochemistry; D013237:Stereoisomerism
chemical_list: C495930:4'-hydroxy-6-nitroflavylium; D000098:Acetophenones; D000475:Alkenes; D009574:Nitro Compounds