@article {6749, title = {Photochemistry of 3,4{\textquoteright}-dimethoxy-7-hydroxyflavylium chloride - Photochromism and excited-state proton transfer}, journal = {Journal of the Chemical Society-Faraday Transactions}, volume = {92}, year = {1996}, note = {

ISI Document Delivery No.: UN958Times Cited: 31
Cited Reference Count: 17
Pina, F Benedito, L Melo, MJ Parola, AJ Bernardo, A
Melo, Maria Joao/C-8594-2011; Pina, Fernando/C-8161-2011; Parola, A. Jorge/F-4048-2010
Parola, A. Jorge/0000-0002-1333-9076
Royal soc chemistry
Cambridge

}, month = {1996}, pages = {1693-1699}, abstract = {

The synthetic compound 3,4{\textquoteright}-dimethoxy-7-hydroxyflavylium chloride gives rise, in aqueous solution at moderately acidic pH, to a pH-dependent equilibrium between the flavylium cation, hemiacetal, (Z)-chalcone and a small amount of quinonoidal base. The distribution, as a function of pH, of the molar fractions of the several species present in solution have been calculated on the basis of H-1 NMR and pH jump experiments monitored by stopped-flow and conventional UV-VIS spectrophotometry, and highperformance liquid chromatography (HPLC). The compound shows interesting photochemical properties: (i) at pH 4.0 it presents a photochromic effect that converts (Z)-chalcone into hemiacetal, the reaction being reversible in the dark and (ii) excited-state proton transfer is observed between the flavylium cation and quinonoidal base. An appropriate formalism to quantify the experimental results has been developed. The formalism allows determination of the pH-dependent molar fraction distribution of the several anthocyanin forms present at equilibrium, as well as predicting the distribution of the molar fractions prior to equilibrium.

}, isbn = {0956-5000}, url = {://WOS:A1996UN95800007}, author = {Pina, F and Benedito, L and Melo, MJ and A. J. Parola and Bernardo, A.} }