heynderickx arnault CINaM

Diarylethenes having perfluorocyclopentene moieties may be promising candidates for these practical applications owing to their excellent characteristics regarding degradation even in the presence of air during photocyclisation. Various diarylethenes can undergo more than 10000 cycles of coloration-bleaching before significant evidence of fatigue. It is worthwhile to note that the thermal stability of the colored closed-ring isomers is dependent on the type of the aryl groups. When the aryl groups are furan, thiophene, selenophene or thiazole rings, the closed form are stable and do not return to the open-ring isomer even at 80°C.
On the other hand, photogenerated closed-ring isomers of diarylethenes with pyrrole, indole or phenyl rings undergo thermally reversible reaction. Other parameters such as bulky substituents, strong electron-withdrawing substituents can assist the thermal reversibility.

In that context, the synthesis of new dipyrrolylperfluorocyclopentenes and their photochromic properties having different p-conjugated chain lengths have been investigated.

Pr. Corinne Moustrou and Dr. Arnault Heynderickx successed in the preparation of eighteen dipyrrolylethenes using a palladium-catalyzed Suzuki reaction , Sonogashira-Hagihara or Wittig-Horner reaction reaction.

A preliminary studie has shown the photochromic behavior of most of them and the impact of substitutions pattern on the half-life time of the colored form.

Fig.1 UV-Vis absorption spectra change of 4 (3.10-5 M in EtOAc) measured at room temperature at different stages of the photochromic reaction. Irradiation (l = 336 nm) intervals are every 2 minutes. (a) starting from open-ring isomer, (b) after irradiation for 2 minutes, (c) 4 minutes, (d) 6 minutes, (e) Photostationary state under irradiation, (f) 30 minutes after irradiation was stopped or after irradiation with 735 nm light for 5 minutes, starting from the photostationnary state.