Effect of Substitution of the Change of Refractive Index in Dithienylethenes: An Ellipsometric Study.

An ellipsometric study was carried out in order to investigate the photoinduced change of the refractive index (Δn) of a series of diarylethenes across the entire spectral range 260–1700 nm. This technique allowed examination of the influence of the resonance conditions on the refractive index. Changing the chemical design of diarylethenes by introducing electron-donating or electron-withdrawing substituents in 5,5′-positions of thiophyene allowed derivation of some correlations between chemical structure and Δn. A strong donor substituent directly linked to the 5,5′-position of the diarylethene moiety gave rise to an increase in the change of the refractive index. 1,2-bis(2-methyl-5-formyl-3-thienyl)perfluorocyclopentene phenyl hydrazone showed a large and stable Δn of 0.005 at 1.5 μm and appeared to be a good candidate for the development of telecommunication devices.