Photochromism of Diarylethenes in DNA-Quaternary Ammonium Ion Complex

The DNA-quaternary ammonium ion complex (DNA-QAIC) is known to form transparent self-standing films. In this article, we have clarified that DNA-QAIC films can be the transparent matrices of photochromic reactions of diarylthenes. The conversion ratio of the diarylethenes to the colored form without hydroxyl groups were almost the same as in solution. Although the diarylethenes with hydroxyl groups can be easily incorporated in DNA-QAIC films, the conversion ratio to the colored forms was much less than that when they were in solution. When 1, 2-bis (2-hydroxymethy1-3-benzothienyl) perfluorocyclopentene was either incorporated in the film or dissolved in chloroform in the presence of DNA-QAIC, no photochromic reaction was observed. It was suggested, from the 1HNMR study, that the conformation of the diarylethene was fixed to a non-cyclizable conformation. In general, a part of the molecule was considered to be intercalated between the DNA base pairs.