New Spiropyrans Showing Crystalline-State Photochromism

Abstract

Photochromic molecules are of great potential importance for optoelectronic devices. This communication presents the preparation of two new spiropyrans that display the first reported crystalline-state photochromism. UV irradiation of the pale yellow form produces the highly colored red form, both in the solid state and in solution. Equilibrium probably proceeds via the open and closed forms shown in the Figure for one of the spiropyrans.