S. Aldoshin et al., A PHOTOCHROMIC PYRIDO-ANNULATED 2,2-DIPHENYLCHROMENE, Acta crystallographica. Section C, Crystal structure communications, 51, 1995, pp. 141-143
A photochromic pyrido-annulated chromene, 3,3-diphenylpyrano[5,6-f]qui
noline, C24H17NO, has been studied. The photoreactive C-sp3-O bond len
gth is longer than the standard values observed for oxygen-containing
heterocycles as a result of steric interactions between the two phenyl
groups.