Multistate/multifunctional systems. A thermodynamic, kinetic, and photochemical investigation of the 4′-dimethylaminoflavylium compound

Ana Roque, Carlos Lodeiro, Fernando Pina, Mauro Maestri, Stephane Dumas, Paolo Passaniti, Vincenzo Balzani

Research output: Contribution to journalArticle

55 Citations (Scopus)

Abstract

The 4′-dimethylaminoflavylium ion in aqueous solution undergoes an intricate network of chemical reactions controlled by pH and light excitation. It is shown that nine different forms are involved, including two species that are not present in previously investigated compounds of the flavylium family. The thermodynamic and kinetic constants of the equilibria and interconversion processes have been obtained by pH jump (included stopped-flow) experiments. The photochromic properties exhibited by the trans/cis chalcone forms have been investigated. The peculiar aspect of 4′-dimethylaminoflavylium, as compared to previously investigated compounds of the same family, is a close to planarity structure, as demonstrated by the X-ray analysis on the parent 4′-aminoflavylium compound (2.3° torsion angle between the benzopyrylium and benzene ring). The results obtained show that the flavylium cation is strongly stabilized by the electron-donor character of the dimethylamino substituent on the benzene ring. The donor-acceptor interaction makes both the protonation of the amino group and the hydration of the flavylium cation difficult, with consequences on the tautomerization and cis/trans isomerization reactions. The multistate/multifunctional properties of 4′-dimethylaminoflavylium have been discussed in the frame of write-lock-read-unlock-erase cycles.

Original languageEnglish
Pages (from-to)987-994
Number of pages8
JournalJournal of the American Chemical Society
Volume125
Issue number4
DOIs
Publication statusPublished - 29 Jan 2003

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