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Moreover, whereas in 2\u2010phenyl\u20102\u2010benzopyrylium compounds <jats:bold>B<\/jats:bold> and <jats:bold>Cc<\/jats:bold> are generally elusive species whose kinetic processes in aqueous solutions occur on the sub\u2010second timescale, in the present compound these species equilibrate on a timescale four orders of magnitude lower. Complete characterization of the equilibrium and kinetics of the reaction network could thus be achieved by <jats:sup>1<\/jats:sup>H\u2005NMR spectroscopy and UV\/Vis spectrophotometry. The network of chemical reactions exhibits <jats:italic>cis<\/jats:italic>\u2013<jats:italic>trans<\/jats:italic> photoisomerization, as well as photochromism between the hemiketal and the chalcone\u2010type species. The irradiation of <jats:bold>Ct<\/jats:bold> in MeOH\/H<jats:sub>2<\/jats:sub>O (1:1) at 365\u2005nm produces <jats:bold>B<\/jats:bold> almost quantitatively through two consecutive photochemical reactions: <jats:bold>Ct<\/jats:bold>\u2192<jats:bold>Cc<\/jats:bold> photoisomerization followed by <jats:bold>Cc<\/jats:bold>\u2192<jats:bold>B<\/jats:bold> photo ring closure with a global quantum yield of 0.02. On the other hand, irradiation of <jats:bold>B<\/jats:bold> at 254\u2005nm leads to a photostationary state composed by 80\u2009% <jats:bold>Ct<\/jats:bold> and 20\u2009% <jats:bold>B<\/jats:bold>, with a quantum yield of 0.21.<\/jats:p>","DOI":"10.1002\/chem.200901884","type":"journal-article","created":{"date-parts":[[2009,11,13]],"date-time":"2009-11-13T11:57:46Z","timestamp":1258113466000},"page":"545-555","source":"Crossref","is-referenced-by-count":18,"title":["Hydroxypyridinechromene and Pyridinechalcone: Two Coupled Photochromic Systems"],"prefix":"10.1002","volume":"16","author":[{"given":"Yoann","family":"Leydet","sequence":"first","affiliation":[]},{"given":"A. 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