Photodegradation of Spirooxazines

From the results reported in the preceding tables, one can state that photochromes having the heterocyclic indoline moiety perform better in terms of both color-ability and fatigue resistance. It is interesting to compare the behavior of 

Tuhte 7. Sxihsiiiuertt l-flectH m the Plmiodegradalhtn (V,n and Cotorahility ( , ,) of Spiiolhcnzodithiolanc-bcnzopyians) tn Toluene (5 10 M unless Otherwise Indicated  

We have seen that photocolorability has been defined as the apparent extinction coefficient eapp= o/[SO]/, where 0is the maximum absorbance after the first flash, [SO] is die concentration of spirooxazine, and l is the pathlength. The parent spirooxazine 8 exhibits absorption at 294 nm, 319 nm, and 350 run with a shoulder 

Colorability is a function of the light flash energy. It was shown that photodecoloration induced by visible light was weak and did not affect color-ability appreciably. For most of the spirooxazines studied, colorability was higher for more dilute solutions (Eapp= 17,500 for [SO] =2 x 10 SM and eaDP = 11,700 for [SO]0 = 2 x indicating the deactivation, at higher 

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 

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