On the photochromic activity of some diphenyl-3H-naphtho[2,1-b]pyran derivatives: synthesis, NMR characterisation and spectrokinetic studies

The synthesis, NMR and mass spectrometric characterisation of a several novel compounds of the naphthopyran family containing either halogen or phosphonate substituents are reported. All of the compounds exhibited photochromic properties in solution and their thermal bleaching after exposure to polychromatic light was monitored using UV-vis spectrophotometry. The bleaching of the merocyanines from these compounds involved two first-order processes, the first of these being more relevant than the second. The effects of substituents upon bleaching kinetics are discussed.