B. Vangemert et al., PHOTOCHROMISM OF DIARYLNAPHTHOPYRANS, Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, 246, 1994, pp. 67-73
A series of 3,3-diaryl-3H-naphtho[2,1-b]pyrans were prepared and their
photochromic properties measured in plastic matrix. The influence of
a variety of substituents on color, intensity, and fade were studied.