Phptotophysics and kinetics of naphthopyran derivatives,part 4: Investigation of [3H]‐naphthopyran kinetics considered as an ABC(2k, 6ϕ) system yielding a monoexponential trace

The elucidation of 3H]‐naphthopyran photochromic kinetics has been dealt with in this investigation by approximating the photocoloring traces as monoexponential. The experimental data have been analyzed, and 13 defining equations of the reactive dynamics have been established. These have been solved simultaneously as a system of nonlinear equations depending on the extinction coefficients and the six possible quantum yields of this ABC type system. The results of this new approach predict that both colored species are directly photochemically produced from the starting material. The most photochemically reactive photoisomer is the most thermally stable and is also the one characterized by the lowest extinction coefficient of the visible absorption band. The mechanism predicted for 3,3‐diphenyl‐3H‐naphtho2,1‐b]pyran in toluene at 30°C obeys ABC(1k,6?) kinetics. © 2006 Wiley Periodicals, Inc. J Chem Kinet 38: 431–438, 2006