Spectral and Physical Properties of Spiroindolinonaphthoxazines

The spectrum of the ring-opened form of the parent spiroindolinonaphthoxazine (1.11) has at 590 mn. Spiroindolinonaphthoxazines also show a negative solva-tochromic shift, the absorption moving hypsochromically (20-60 nm) in less polar solvents (e.g. toluene versus ethanol), the converse of what happens with spiroin-dolinobenzopyrans (see section 1.2.2.2). 

Introduction of dialkylamino substituents in the 6 -position of the spiroindolinonaphthoxazine (1.11) causes a hypsochromic shift in the absorption maximum of the coloured state and also an increase in its intensity. This hypsochromic shift can also be increased by introducing electron-withdrawing groups into the 5-position of (1.11), whilst electron-donating groups move the absorption maximum in the opposite direction. The data for these effects are given in Table 1.3. 

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