Oxidation in Dark Reactions of Spirooxazines

Malatesta el al.47 have shown that thermal dark reactions yield the same intermediate oxidation product(s) as those formed during photodegradation as a result of electron-transfer processes from SO or its MC form to a suitable electron acceptor EA, such as 7,7,8,8-tetracyanoquinodimethane (TCNQ, 316). 

When CuCl2 was used as oxidizing (EA) agent, a complex salt of similar structure was isolated in which the anion was CuCl2-. This salt showed no conductivity. The existence of a thermal degradation route of the type reported above renders even more complex the task of designing a spirooxazine endowed with high stability with respect to photoexcitation. From what has been reported 

H[urr 26l Crystal structure of the TtNQ-j/317 complex (TCNQ = .T,B.8.-ttUzcyafniKniinodi-m ethane) TCNQ/TCNQ couples alternate along the crysi l e axis, farming helical substructure. (Reprinted from Ref. 47 with permiMiom of the American Chemical Society.  

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