Effects of Substituents on the Indoline Ring on the Negative Photochromic Properties of Spirobenzopyran Derivatives

Novel substituted -6,8-dinitro-l′,3′,3′-trimethylspiro[2H-1-benzopyran-2,2′-indoline] derivatives have been synthesized in high yields, and their properties are investigated. The absorption maxima of the ring-open forms and the negative photochromic properties of spirobenzopyrans significantly depend on the substituents in the indoline ring and on the nature of the solvent used.