Photochromic cyclization/cycloreversion

Dithienylethene and derivatives. l,2-Di(2,5-dimethylthien-3-yl)cyclopentene and its derivatives are generally termed dithienylethenes or diarylethenes. Their photochromic properties with the reversible cyclization/cycloreversion are fascinating for chemist and material scientists and have been widely applied to photoswitch, optical memory, etc. in molecular devices and in nanotechnology. Therefore, many researchers are seeking possibilities to move the frontiers. In the last two years many novel dithienylethenes have been prepared and their photochromie properties were investigated. 

In solution, 10a showed typical photochromic behavior on irradiation with UV and visible light (Fig. 9.4). Although the radical moiety has a weak absorption in the region from 550 to 700 nm, this did not prevent the photochromic reaction. Almost 100 % photochemical conversions were observed in both the cyclization from the open-ring isomer 10a to the closed-ring isomer 10b and the cycloreversion from 10b to 10a. For the practical use of photochromic devices, high conversion is one of the most important characteristics. 

The compound was found to have excellent photochromic and fluorescence properties in solution. The photochromic kinetics showed the cyclization processes is zero order and the cycloreversion is first order. 

Some selected examples of 1,2-diarylethenes were shown in this review. Miyasaka and Irie et al. revealed the three-photon cyclization and two-photon cycloreversion of diarylethens (223) by a near-infrared femtosecond laser pulse at 1.28 pm. They also found single-molecule fluorescence photoswitching of a diarylethene-perylenebisimide dyad (225)." " Photomechanical effects of two-component cocrystal (226) composed of 1,2-diarylethene derivative and perfluoronaphthalene or hydrogen-bonded diarylethene-imidazoline crystalline (227) were examined. A variety of photochromic reactions of 1,2-diarylethenes in crystalline states were reported by Iiie et al. ... 

Mori K, Ishibashi Y, Matsuda H, Ito S, Nagasawa Y, Nakagawa H, Uchida K, Yokojima S, Nakamura S, Irie M, Miyasaka H (2011) One-color reversible control of photochromic reactions in a diarylethene derivative three-photon cyclization and two-photon cycloreversion by a near-infrared femtosecond laser pulse at 1.28 pm. J Am Chem Soc 133 2621-2625... 

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