Hirumi Yohei, Tamaki Kento, Namikawa Tomotaka, Kamada Kenji, Mitsui Masaaki, Suzuki Kengo, Kobayashi Kenji
Department of Chemistry, Graduate School of Science, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529 (Japan), Fax: (+81) 54-238-4933.
Chem Asian J. 2014 May;9(5):1282-90. doi: 10.1002/asia.201400042. Epub 2014 Feb 25.
The self-assembled boronic ester cavitand capsule 3 quantitatively and tightly encapsulates 2,6-diacetoxy-9,10-bis(arylethynyl)anthracene derivatives 4 a-4 c as highly fluorescent cruciform guests to form complexes 4 a@3, 4 b@3, and 4 c@(3)2. The structural features of capsule 3, which possesses two polar bowl-shaped aromatic cavity ends and four large equatorial windows connected by dynamic boronic ester bonds, made it possible to encapsulate cruciform 4 with protection of the reactive anthracene core inside the capsule and with two protruding arylethynyl groups, the π-conjugated arms of compound 4, through two of the equatorial windows of the capsule. Thus, complexes 4 a@3, 4 b@3, and 4 c@(3)2 show greater resistance to photochemical reactions in solution and fluorescence quenching in the powder state compared to free guests 4. In addition to the improved photostability, restriction of the free rotation of the arylethynyl groups of guests 4 upon encapsulation results in sharpening of the UV/Vis absorption peaks with a red-shift and a significant increase in some of the two-photon-absorption peaks of complexes 4 a@3, 4 b@3, and 4 c@(3)2 compared with free guests 4.
自组装硼酸酯穴状配体胶囊3能定量且紧密地包封2,6 - 二乙酰氧基 - 9,10 - 双（芳基乙炔基）蒽衍生物4 a - 4 c，这些衍生物作为高荧光十字形客体，形成配合物4 a@3、4 b@3和4 c@(3)2。胶囊3具有两个极性碗状芳香腔末端以及通过动态硼酸酯键相连的四个大的赤道窗口，其结构特征使得它能够包封十字形客体4，将反应性蒽核保护在胶囊内部，并且使化合物4的π共轭臂——两个突出的芳基乙炔基通过胶囊的两个赤道窗口伸出。因此，与游离客体4相比，配合物4 a@3、4 b@3和4 c@(3)2在溶液中对光化学反应以及在粉末状态下对荧光猝灭表现出更强的抗性。除了光稳定性提高外，客体4的芳基乙炔基在包封后自由旋转受限，导致配合物4 a@3、4 b@3和4 c@(3)2的紫外/可见吸收峰变尖锐且发生红移，并且其二光子吸收峰中的一些相比游离客体4有显著增加。
