Seo Joobeom, Matsuda Ryotaro, Sakamoto Hirotoshi, Bonneau Charlotte, Kitagawa Susumu
Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
J Am Chem Soc. 2009 Sep 9;131(35):12792-800. doi: 10.1021/ja904363b.
The design of pore properties utilizing flexible motifs and functional groups is of importance to obtain porous coordination polymers with desirable functions. We have prepared a 3D pillared-layer coordination polymer, {[Cd(2)(pzdc)(2)L(H(2)O)(2)].5(H(2)O).(CH(3)CH(2)OH)}(n) (1, H(2)pzdc = 2,3-pyrazinedicarboxylic acid; L = 2,5-bis(2-hydroxyethoxy)-1,4-bis(4-pyridyl)benzene) showing (i) a rotatable pillar bearing ethylene glycol side chains acting as a molecular gate with locking/unlocking interactions triggered by guest inclusion between the side chains, (ii) framework flexibility with slippage of the layers, and (iii) coordinatively unsaturated metal centers as guest accessible sites through the removal of the water coligands. The framework clearly shows reversible single-crystal-to-single-crystal transformations in response to the removal and rebinding of guest molecules, the observation of these processes has provided fundamental clues to the understanding of the sorption profiles. The X-ray structures indicate that the 3D host framework is retained during the transformations, involving mainly rotation of the pillars and slippage of the layers. The structure of dried form 2, Cd(2)(pzdc)(2)L, has no void volume and no water coligands. Interestingly, the adsorption isotherm of water for 2 at 298 K exhibits three distinct steps coinciding with the framework functions. Compound 2 favors the uptake of CO(2) (195 K) over N(2) (77 K) and O(2) (77 K). Above all, we report on a molecular gate with a rotational module exhibiting a locking/unlocking system which accounts for gate-opening type sorption profiles.
利用柔性基序和官能团设计孔隙特性对于获得具有理想功能的多孔配位聚合物至关重要。我们制备了一种三维柱状层状配位聚合物{[Cd(2)(pzdc)(2)L(H₂O)(2)].5(H₂O).(CH₃CH₂OH)}(n) (1，H₂pzdc = 2,3 - 吡嗪二甲酸；L = 2,5 - 双(2 - 羟基乙氧基)-1,4 - 双(4 - 吡啶基)苯)，该聚合物表现出：(i) 带有乙二醇侧链的可旋转支柱，其作为分子门，通过侧链间客体包合引发锁定/解锁相互作用；(ii) 具有层滑动的骨架柔性；(iii) 通过去除水配体形成可被客体接近的配位不饱和金属中心。该骨架在客体分子的去除和重新结合时明显表现出可逆的单晶到单晶转变，对这些过程的观察为理解吸附曲线提供了基本线索。X射线结构表明，三维主体骨架在转变过程中得以保留，主要涉及支柱的旋转和层的滑动。干燥形式2 Cd(2)(pzdc)(2)L 的结构没有空隙体积且没有水配体。有趣的是，2在298 K时对水的吸附等温线呈现出与骨架功能相符的三个不同步骤。化合物2在195 K时对CO₂的吸附优于在77 K时对N₂和O₂的吸附。最重要的是，我们报道了一种具有旋转模块的分子门，其展示了一种锁定/解锁系统，该系统解释了开门型吸附曲线。
