Spirooxazines photodegradation

Spirooxazines - a family of compounds proven quite useful because of their resistance to photodegradation, commonly called fatigue ... 

Indolinospirooxazines are inherently more fatigue resistant than the spiropyr-ans. As measured by the quantum yield for photodegradation, the spironaphthox-azines are two or three orders of magnitude more photostable than the spirobenzopyrans. 37 From the point of view of industrial applications, spirooxazines are reported to be stabilized even further by various protective methods. 

The main focus of this chapter is on two well-studied series of photochromic compounds, spiropyrans and spirooxazines, and the comparison of their photo-reactive excited states and molecular structures. The discussion of their photodegradation takes into account the results obtained from spectrophotometric measurements together with the identification of the fragments resulting from photodegradation. Different mechanisms are proposed for the photooxidation reaction. The experimental apparatus and procedures for photodegradation studies are also described. 

Photodegradation is a function of the light flash energy and irradiation wavelength. By increasing the flash energy, photocoloration is improved whereas photostability decreases. For unfiltered light, = 20-37 for most of the spirooxazines studied. Colorability dropped by a factor of ca. 2 when a Wood... 

Topics which have formed the subjects of reviews this year include photoinduced organic synthesis, photoisomerisations involving super-cyclophanes, regioselec-tive and stereoselective [2+2] photocycloadditions, position- and stereoselective photocyclisation, the photochemistry of indoles, five-membered heterocyclic compounds of the indigo group, pyrazoles and isothiazoles, and heterocyclic N-oxides, photochromic reactions of naphthopyran derivatives, photodegradation reactions of photochromic spirooxazines and 2H-chromenes, ° and chiral photo-chromic compounds. ... 

Pardo, R., Zayat, M., and Levy, D. (2012) Stability against photodegradation of a photochromic spirooxazine dye embedded in amino-functionalized sol-gel hybrid coatings. /. Sol-Gel Sci Technoi, 63, 400-407. 

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