Kingo Uchida

Publications (53) View all

• Article: Potential energy surfaces and quantum yields for photochromic diarylethene reactions.

  Shinichiro Nakamura, Kingo Uchida, Makoto Hatakeyama
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  ABSTRACT: Photochromic diarylethenes (DAEs) are among the most promising molecular switching systems for future molecular electronics. Numerous derivatives have been synthesized recently, and experimental quantum yields (QYs) have been reported for two categories of them. Although the QY is one of the most important properties in various applications, it is also the most difficult property to predict before a molecule is actually synthesized. We have previously reported preliminary theoretical studies on what determines the QYs in both categories of DAE derivatives. Here, reflecting theoretical analyses of potential energy surfaces and recent experimental results, a rational explanation of the general guiding principle for QY design is presented for future molecular design.
  Molecules 01/2013; 18(5):5091-103. · 2.39 Impact Factor
• Article: Photoinduced Formation of Superhydrophobic Surface on which Contact Angle of a Water Droplet Exceeds 170° by Reversible Topographical Changes on a Diarylethene Microcrystalline Surface.

  Naoki Nishikawa, Hiroyuki Kiyohara, Shingo Sakiyama, Seiji Yamazoe, Hiroyuki Mayama, Tsuyoshi Tsujioka, Yuko Kojima, Satoshi Yokojima, Shinichiro Nakamura, Kingo Uchida
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  ABSTRACT: A superhydrophobic surface on which the contact angle of a water droplet exceeds 170° was reversibly produced by alternate irradiation with UV and visible light. Superhydrophobicity is due to the formation of densely generated sub-micrometer sized needle-shaped crystals (less than 0.2~0.3 micrometer diameter and 10 micrometer long) at 30 °C, which is much lower than the eutectic temperature of either isomers of the diarylethene. Below eutectic temperature, the generated crystals were much smaller than those generated above eutectic temperature. These smaller crystals more effectively enhanced the superhydrophobicity.
  Langmuir 12/2012; · 4.19 Impact Factor
• Article: Photochromism of 2-Thienylperfluorocyclopentene Derivatives: Substituent Effect on the Reactive Carbon Atoms.

  Yuto Tatsumi, Jun-Ichiro Kitai, Waka Uchida, Koji Ogata, Shinichiro Nakamura, Kingo Uchida
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  ABSTRACT: In this work, we prepared a new 1,2-bis(3-cyanothiophen-2-yl)perfluorocyclopentene with electro-withdrawing cyano groups at both reactive carbon atoms. Furthermore, we studied the substituent effects of the reactive carbon atoms on the photochromic properties of 1,2-bis(3-R-substituredthiophen-2-yl)perfluorocyclopentene derivatives by comparing the absorption wavelengths and quantum yields of the derivatives having R=cyano, methyl, and methoxy groups. The absorption bands of the closed-ring isomers generated by UV irradiation shifted to longer wavelengths with an increase in the electron-donating characteristic of the substituents. The closed-ring isomer having cyano groups at both reactive carbon atoms has an absorption band at 427 nm (λmax), while those of methyl and methoxy derivatives have bands at 432 and 481 nm respectively. The derivative with cyano groups shows the largest cycloreversion quantum yield (0.45), and this yield decreased with an increase in the substituents' donating characteristic. Theoretical calculation explains that the excited state of the closed-ring isomer with cyano groups has the highest energy, since there is no barrier to ring opening on the excited potential surface.
  The Journal of Physical Chemistry A 10/2012; · 2.95 Impact Factor
• Article: Photochromism of a diarylethene having an azulene ring.

  Jun-ichiro Kitai, Takao Kobayashi, Waka Uchida, Makoto Hatakeyama, Satoshi Yokojima, Shinichiro Nakamura, Kingo Uchida
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  ABSTRACT: Diarylethene derivatives incorporating an azulene ring at the ethene moiety were synthesized. One derivative having thiazole rings showed the expected coloration reaction by excitation at 313 nm (to a higher singlet state) but not when excited at 635 nm (S(0) to S(1) excitation). The system demonstrates that the cyclization reaction can be controlled by selective excitation at different wavelengths of the absorption spectrum. On the other hand, another derivative having thiophene rings did not show any photochromism. The results clearly show the importance of the coplanarity of the system for the photoisomerization.
  The Journal of Organic Chemistry 03/2012; 77(7):3270-6. · 4.45 Impact Factor
• Article: Water-soluble argatroban for antithrombogenic surface coating of tissue-engineered cardiovascular tissues.

  Yasuhide Nakayama, Saori Yamaoka, Masashi Yamanami, Megumi Fujiwara, Masami Uechi, Keiichi Takamizawa, Hatsue Ishibashi-Ueda, Marie Nakamichi, Kingo Uchida, Taiji Watanabe, Keiichi Kanda, Hitoshi Yaku
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  ABSTRACT: Argatroban is a powerful synthetic anticoagulant, but due to its water-insoluble nature, it is unsuitable for use as a coating material to reduce the thrombogenic potential of natural or tissue-engineered blood-contacting cardiovascular tissues. On the other hand, anionic compounds could adsorb firmly onto connective tissues. Therefore, in this study, an anionic form of argatroban was prepared by neutralization from its alkaline solution, dialysis, and freeze-drying. The subsequently obtained argatroban derivative could be easily dissolved in water. Analysis of the surface chemical composition showed that the water-soluble argatroban (WSA) could be adsorbed on the entire surface of tissue-engineered connective tissue sheets composed mainly of collagen. Adsorption was achieved on immersion of the tissue-engineered connective tissue sheet in a saline/WSA solution for only 30 s without any change in the mechanical properties of the tissue-engineered sheets. Complete surface adsorption (ca., 1 mg/cm(2) ) was obtained at WSA concentrations of over 5 mg/mL. WSA adsorption was maintained for at least 7 days with rinsing. Blood coagulation was significantly prevented on the WSA-adsorbed surfaces in acute in vitro experiments. The coating was applied to in vivo tissue-engineered vascular grafts (biotubes) or tri-leaflet tissues (biovalves) under development, ensuring a high likelihood of nonthrombogenicity of their blood-contacting surfaces with high patency, at least in the subchronic phase. It appears that WSA satisfies the initial requirements for a biocompatible aqueous coating material for use in natural or tissue-engineered tissues.
  Journal of Biomedical Materials Research Part B Applied Biomaterials 09/2011; 99(2):420-30. · 2.15 Impact Factor