X-ray diffraction measurements for a diarylethene single crystal for time-resolved femtosecond X-ray diffraction

Photoreactions in organic compounds are very basic reactions in biology and chemistry, and have also been applied to engineering such as for optical memory and optical switch. Diarylethene is one of the photo reactive artificial organic compounds that are expected to find use in various optical applications. So far, several papers have showed photoreactions in diarylethenes occur in two stages; excitation in less than a few hundreds of femtosecond and relaxation in several picoseconds, with optical pump-prove measurements. However, the whole mechanism of the photoreaction has not been clarified yet because of the difficulty in observing molecular movements with atomic-scale spatial resolution in femtosecond-to-picosecond time scale, which is inevitable to elucidate the whole mechanism of the photoreaction. Time-resolved femtosecond X-ray diffraction (FXD), which satisfies both femtosecond-to-picosecond time resolution and atomic-scale spatial resolution, is considered to be an effective method to observe molecular movements during photoreactions directly. Here we conducted static X-ray diffraction (XRD) measurements for single crystals we performed of 1,2-bis(3,5-dimethyl-2-thienyl)perfluoro-cyclopentene, which is a diarylethene derivative. These XRD results suggest that the single crystals are satisfied with the necessary conditions for FXD. (author)