Diarylethene

The dihydrophenanthrene intermediate has never been isolated, but it has been detected spectroscopically in pump-probe experiments by virtue of its long wavelength optical absorption band.

Following the Woodward–Hoffmann rules, the photochemical 6π cyclization takes place in a conrotatory fashion, leading to products with an anti configuration of the methyl substituents.

[7] This approach also has the advantage that the thermal (disrotatory) ring closure can not take place because of steric hindrance between the substitution groups.

More recently, based on recent findings showing that by-product formation most likely occurs exclusively from the lowest singlet excited state,[9][10] a superior fatigue resistance of dithienylethenes upon visible-light excitation has been achieved by attaching small triplet-sensitizing moieties to the diarylethene core via a π-conjugated linkage.

Moreover, these two isomers differ from one another not only in their absorption spectra but also in various physical and chemical properties, such as their refractive index, dielectric constant, and oxidation-reduction potential.

This allows for the electronic communication between functional groups attached to the far ends of the diarylethene to be switched on and off using UV and visible light.