HIGH PHOTODEGRADABILITY OF SPIRO[FLUORENE-[2H]-CHROMENES]

The photodegradation of photochromic compounds in spiro[fluorene-[2H]- chromene] series in toluene has been studied by continuous irradiation . We have shown that the resistance to the photodegradation is a funct ion of the introduced heterocycle, As in spiro[indoline-naphthoxazine] series, the chromenes heteroannelled by a benzofurane or a pentamethy lene pattern present a dramatic decrease of their resistance to the ph otodegradation, Then, comparatively to the diaryl-[2H]-chromenes, the increasing flatness of the open forms issued from the spiro[fluorene-[ 2H]chromenes] leads to a lower stability in connection with a bathochr omic shift and the apparition of an additional band in the visible spe ctrum.