Substitution on the Naphthoxazine Ring Moiety

Hovey et al.3 reported an enhancement in photochromic response by the addition of a methoxy group in the 9 -position or a bromine in the 8 -position, as shown in Table 2.1. Although dramatically improving the photochromic response, these substituents had little effect on the position of the visible absorption band. 

A more interesting result arises from attaching an amino group on the 6 -position of NISO. The addition of an alicyclic amino group in the 6 -position (see 

The presence of a methoxy group in the 5 -position (compound 3) causes a shift in the thermal equilibrium between the uncolored and colored species toward the colored species. 

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