HETEROCYCLO-ANNULATED SPIROOXAZINES AND 2H-CHROMENES - 2 COMPLEMENTARY SERIES OF PHOTOCHROMIC COMPOUNDS

Our purpose was to prepare heterocyclo-annulated spirooxazines and 2H- chromenes in order to extend the scale of the main photochromic proper ties (spectro-kinetical and photodegradation parameters) and to charac terize the influence of the nature and positions of heteroatoms. - Nit rogenated six-ringed systems have very slight influence on k(Delta), l ambda(max) and colorability of the photomerocyanines but an interestin g power of enhancing the resistance to the fatigue. On the other hand the polyheteroatomic five-ringed systems present a broadening of the v isible absorption spectrum but the photodegradation behaviour is not s o satisfying. - The replacement of the indoline moiety by hindered aza heterocyclic systems has also an interesting effect on the visible abs orption and for) the thermal bleaching kinetics. - The accumulation of benzene nuclei and nitrogen atoms especially in the case of a 7-8 ann ulation on the spirobenzoxazine skeleton shifts the photochromic equil ibrium toward a permanent merocyanine, the transoid structure of which has been studied by X-Ray diffraction, H-1 NMR and dipole moment. All these data are in agreement with a quinoid or polyenic electron distr ibution. As a conclusion, the heterocyclic annulation is a good means for modulating the photochromic properties and can be coupled also to the effect of substitutents.