Novel photochromic spirocyclic compounds of thienopyrroline series: 1: Spiropyrans

Novel spiropyrans of the thienopyrroline series have been synthesized and their photochromic properties studied and compared with those of the indoline analogues. As compared with the indoline analogues, the absorption bands of the cyclic forms of the thienopyrroline spiropyrans are shifted to the blue spectral region, whereas those of the ring-opened forms are shifted to the red region. The merocyanine isomers of the thienopyrroline spiropyrans demonstrate greater thermal stability than their indoline analogues. At the same time thienopyrroline spiropyrans are more photodegradable and less fatigue resistant than the indoline congeners.