Novel compounds producing a photochromic spiropyran on heating

The synthesis and properties of merocyanine-pyrrole adducts, which are irreversible and quantitatively reverted to the original photochromic spiropyran and pyrrole by a thermal reaction, are described. The merocyanine-pyrrole adducts were synthesized by the reaction of 1',3',3'-trimethyl-6-nitrospiro [2H-1 -benzopyran-2,2'-indoline] derivatives with 1-pyrrolylpotassium in THF at room temperature. Though, these compounds are amorphous solids and stable at room temperature, by partial heating at 130 degreesC in a polymer matrix him, they quantitatively decomposed to the original spiropyran remaining in the matrix such as the polymer film and to pyrrole missing from the matrix due to the vaporization. Therefore, photochromic patterns will be formed in the polymer film. (C) 2001 Elsevier Science B.V. All rights reserved.