Quantum efficiencies of merocyanine formation,(ΦA), have been measured for several
naphthoxy-spiro-indolines,(NOSIs) in a variety of solvents as well as in several polyurethane
matrices having different glass-transition temperatures. In toluene solution ΦA values range
from 0.74 to 0.33 with those compounds substituted with electron-donating substituents in
the 6′-position on the oxazine ring giving the highest yields. Quantum yields for
merocyanine formation are also sensitive to change of solvent, being the highest in toluene …

Naphthoxazine-spiro-indolines (NOSIs) can exist in a colourless and a coloured form. These
compounds can interconvert between these two forms either photochemically or thermally
and are resilient to degradation even after repeated cycles of colouration and bleaching.
Absorption spectra of both the stable colourless form and the energetically less stable
coloured form have been measured. Several NOSI compounds have been shown to
photoconvert to the coloured form with an efficiency of between 0.06–0.74, depending upon …