A Photochromic Diarylethene Compound

Diarylethenes are typical photochromic [3] molecules, in which the thermodynamically stable colorless open-ring isomer is converted to the colored closed-ring isomer upon irradiation (see, for example. Fig. 4.10), whereas the reverse reaction is either thermally or photochemicaUy activated [27, 28]. 

2-bis(5-(4-ethynylphenyl)-2-methylthiophen-3-yl)perfluorocyclopentene diarylethene derivative (1), shown in Fig 4.10, has usefiil spectroscopic properties, since it covers a wide spectral range, and is thermally stable in both isomeric forms [28]. Therefore, the photochemical behaviour as well as the fatigue resistance properties of 1 have been recently studied in detail by us [29] since its absorption spectrum extends in the visible up to about 700 nm and very simple practical procedures are required by photochromic actinometers, this system has also been proposed as a new chemical actinometer [29]. We report here, as an example, the experimental conditions and the actinometers used in this research, the main results obtained and the procedure suggested for the use of this compound as actinometer. 

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