Towards grey coloring photochromic materials using vinylidene-naphthofurans

Abstract A series of substituted vinylidene-naphthofurans were prepared from 2-naphthols. These compounds show both acido- and photochromism, at room temperature, developing different colorations that can be switched back to the initial uncolored state by the addition of base or removal of the light source. The introduction of electron-donating substituents in the right position leads to a significant bathochromic shift providing compounds that can generate brown/grey colors. These photoactive dyes were dispersed in polymeric materials proving photochromic materials that switch between the uncolored/colored states, in a few minutes, at room temperature.