Substituent effect on photochromism of indolinospirooxazines

The photochromic reactions of five indolinospirooxazine derivatives ( II, III, V and VII) were examined using nanosecond laser flash photolysis techniques. Photolysis of II–V leads to the formation of long-lived photomerocyanines (PMCs), whereas the only detectable product in the photolysis of CII is a short-lived, charge-separated, twisted species (CT intermediate). The results show that the substituent in the 2′ position of the oxazine ring has a decisive role on the photochromic reaction products and all of the substituents influence the absorption maxima of the photoproducts of indolinospirooxazines. A proposed potential energy surface model has been established to explain these phenomena. Moreover, the characteristics of the absorption spectra of the PMCs and CT intermediate are discussed.