Photo- and Thermochromic Spiropyrans 42.* The Effect of Structural Factors on the Photochromic Properties of Indolinospiro-Pyrans Containing a Condensed Furan Fragment

Syntheses are reported for a series of N-substituted indolinospiropyrans containing a fused furan fragment in the benzopyran part of the molecule. The structure of these compounds was established by IR and multinuclear NMR spectroscopy. A study was carried out on the effect of the fused benzene ring and bulky N-benzyl substituent on the photochromic properties of these compounds in solution and in a polymer matrix. Dynamic NMR spectroscopy was used to study the thermally induced isomerization of the N-benzyl derivative.