{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,19]],"date-time":"2025-10-19T18:20:59Z","timestamp":1760898059262,"version":"build-2065373602"},"reference-count":29,"publisher":"Wiley","issue":"23","license":[{"start":{"date-parts":[[2011,4,19]],"date-time":"2011-04-19T00:00:00Z","timestamp":1303171200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Chemistry A European J"],"published-print":{"date-parts":[[2011,5,27]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>A symmetric bis(flavylium) constituted by two 7\u2010hydroxyflavylium moieties linked by a methylviologen bridge was synthesized. The thermodynamic and kinetics of the network of chemical reactions involving bis(flavylium) and the model compound 7\u2010hydroxy\u20104\u2032\u2010methylflavylium was completely characterized by means of direct and reverse pH jumps (stopped flow) and flash photolysis. Both compounds follow the usual pH\u2010dependent network of chemical reactions of flavylium derivatives. The equilibrium species of the model compound are the flavylium cation (acidic species) and the <jats:italic>trans<\/jats:italic>\u2010chalcone (basic species) with an apparent p<jats:italic>K<\/jats:italic>\u2032<jats:sub>a<\/jats:sub>=2.85. In the case of the bis(flavylium) it was possible to characterize by <jats:sup>1<\/jats:sup>H\u2005NMR spectroscopy three species with different degrees of isomerization: all flavylium, flavylium\u2010<jats:italic>trans<\/jats:italic>\u2010chalcone, and all <jats:italic>trans<\/jats:italic>\u2010chalcone. Representation of the time\u2010dependent mole fraction distribution of these three forms after a pH jump from equilibrated solutions of all\u2010flavylium cation (lower pH values) to higher pH values, shows that formation of <jats:italic>trans<\/jats:italic>\u2010chalcone is not completely stochastic (two independent isomerizations), the isomerization of one flavylium showing a small influence on the isomerization of the other. The radical of the methyl viologen bridge is formed upon reduction of the bis(<jats:italic>trans<\/jats:italic>\u2010chalcone) with dithionite. The system is reversible after addition of an oxidant in spite of the occurrence of some decomposition.<\/jats:p>","DOI":"10.1002\/chem.201003726","type":"journal-article","created":{"date-parts":[[2011,4,19]],"date-time":"2011-04-19T09:28:16Z","timestamp":1303205296000},"page":"6359-6368","source":"Crossref","is-referenced-by-count":9,"title":["Synthesis and Characterization of a Symmetric Bis(7\u2010hydroxyflavylium) Containing a Methyl Viologen Bridge"],"prefix":"10.1002","volume":"17","author":[{"given":"Ana M.","family":"Diniz","sequence":"first","affiliation":[]},{"given":"Carlos","family":"Pinheiro","sequence":"additional","affiliation":[]},{"given":"Vesselin","family":"Petrov","sequence":"additional","affiliation":[]},{"given":"A. 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