Refractive index changes of amorphous diarylethenes containing 2,4-diphenylphenyl substituents

Photochromic diarylethene derivatives containing 2,4-diphenylphenyl substituents formed stable amorphous solids and showed reversible solid-state photochromism. Refractive indices of the amorphous films changed reversibly with the photochromic reactions as much as Deltan = 0.028 at 817 nm. Changes in both absorption band and static polarizability contributed to the large refractive index modulation.