An NMR investigation of the merocyanine dyes generated by protolysis of some novel spironaphthopyranoindoles

Two novel amino-substituted spiroindolinonaphthopyrans have been synthesised. Whilst these compounds exhibit no observable photochromic properties at ambient temperature, protonation gives stable, intensely coloured dyes. 1H nmr spectroscopy has been used to establish the configuration of these dyes.