The whole photochromic reaction, photocolouration, thermal bleaching and photodegradation, of a quinolone derivative has been kinetically monitored by product-by-product NMR spectroscopy. The mechanism of reactions has been established from quantitative kinetic data analysis. (c) 2006 Elsevier Ltd. All rights reserved.
NMR structural elucidation of photochromic quinolone photoproducts
UV irradiation of 3-benzoyl-2-benzyl-6,7-difluoro-1-propyl-1H-quinolin-4-one leads to the formation of a mixture of photoproducts, with different evolutions. The structure of each of them has been obtained by one- and two-dimensional multinuclear NMR experiments. Two photoenols, which are thermally reversible, have been identified. All of the other photoproducts have been assigned to degradation. Based on the structural identification and the photochemical and thermal evolution of samples, a plausible mechanism is proposed. (c) 2005 Elsevier Ltd. All rights reserved.