Synthesis of Photochromic Lactone-Fused Naphthopyrans With Extended Visible Light Absorption

The synthesis of new photochromic lactone-fused naphthopyrans substituted with arylethenyl groups is discussed. Brief exposure of solutions of these colorless compounds to the UV light results in the generation of intense hues, which spontaneously return to the uncolored state within seconds after removing the light source. As anticipated, introducing the ethenyl bonds caused a bathochromic shift in the absorption spectrum of the opened colored photoisomers, however, due to non-uniform absorption across the visible spectrum, the perceived color ranged from red to brownish-red.