Yamamoto Katsuya, Mutoh Katsuya, Abe Jiro
Department of Chemistry, School of Science and Engineering , Aoyama Gakuin University , 5-10-1 Fuchinobe , Chuo-ku, Sagamihara, Kanagawa 252-5258 , Japan.
J Phys Chem A. 2019 Mar 14;123(10):1945-1952. doi: 10.1021/acs.jpca.8b12384. Epub 2019 Mar 5.
Fast photochromic molecules have received much interest in the potential application as a real-time switching trigger in material and biological chemistry. Pentaarylbiimidazole (PABI) and phenoxyl-imidazolyl radical complex (PIC) are one of the fast photochromic molecules based on imidazolyl radicals. Because the photochromic reaction of these fast photochromic molecules proceeds from the optically forbidden S state, it is difficult to estimate the excitation energy to induce the photochromic reactions by spectroscopic techniques. In this study, we performed the electrochemical measurements for PABI and PIC to investigate the electronic properties and to determine the S-S transition energies. In addition, we also revealed that the electrochemical reduction of PABI and PIC generates the radical anion which spontaneously shows the C-N bond breaking reaction to produce the radical species. The initial photochromic dimer is reproduced by the reversible oxidation of the anion species. This characteristic photochromic and electrochromic properties can be applicable to the photowritable electrochromic devices with high spatial resolution.
快速光致变色分子在材料和生物化学领域作为实时切换触发器的潜在应用中受到了广泛关注。五芳基联咪唑（PABI）和苯氧基 - 咪唑基自由基配合物（PIC）是基于咪唑基自由基的快速光致变色分子之一。由于这些快速光致变色分子的光致变色反应从光学禁阻的S态开始，通过光谱技术很难估计诱导光致变色反应的激发能。在本研究中，我们对PABI和PIC进行了电化学测量，以研究其电子性质并确定S - S跃迁能。此外，我们还发现PABI和PIC的电化学还原会生成自由基阴离子，该阴离子会自发地发生C - N键断裂反应以产生自由基物种。通过阴离子物种的可逆氧化可以重现初始的光致变色二聚体。这种独特的光致变色和电致变色性质可应用于具有高空间分辨率的光写入电致变色器件。
