Cyclization from Higher Excited States of Diarylethenes Having a Substituted Azulene Ring.

The cyclization reaction of diarylethenes having an azulene ring occurs only via higher excited states. Novel diarylethenes having an azulene ring with a strong donor or acceptor were synthesized and examined in these reactions. A derivative having an electron-donating 1,3-benzodithiol-2-ylidenemethyl group at the 1-position of the azulene ring showed photochromism, whereas neither a derivative having a π-conjugated electron-donating group at the 3-position of the azulene ring nor derivatives having a π-conjugated electron-withdrawing group at the 1- or 3-position of the azulene ring showed any photochromism.

Photoinduced macroscopic morphological transformation of an amphiphilic diarylethene assembly: reversible dynamic motion.

Self-assembled microstructures of an amphiphilic diarylethene featuring an alkyl chain and triethylene glycol groups showed a photoinduced reversible morphological change in water. Reversible photoisomerization of the core diarylethene gave rise to a reversible morphological transformation between colorless microspheres and colored fibers. When colorless microspheres were irradiated with UV light, colored fibers were formed, and when the colored fibers were irradiated with visible light, the spheres were restored to their original positions where the spheres originally existed.

Photochromism of 1,2-bis(2-thienyl)perfluorocyclopentene derivatives: substituent effect on the reactive carbon atoms.

In this work, we prepared a new 1,2-bis(3-cyanothiophen-2-yl)perfluorocyclopentene with electro-withdrawing cyano groups at both reactive carbon atoms. Furthermore, we studied the substituent effects of the reactive carbon atoms on the photochromic properties of 1,2-bis(3-R-substituted thiophen-2-yl)perfluorocyclopentene derivatives by comparing the absorption wavelengths and quantum yields of the derivatives having R = cyano, methyl, and methoxy groups. The absorption bands of the closed-ring isomers generated by UV irradiation shifted to longer wavelengths with an increase in the electron-donating characteristic of the substituents.

Photochromism of a diarylethene having an azulene ring.

Diarylethene derivatives incorporating an azulene ring at the ethene moiety were synthesized. One derivative having thiazole rings showed the expected coloration reaction by excitation at 313 nm (to a higher singlet state) but not when excited at 635 nm (S(0) to S(1) excitation). The system demonstrates that the cyclization reaction can be controlled by selective excitation at different wavelengths of the absorption spectrum.