The Catalytic Z to E Isomerization of Stilbenes in a Photosensitizing Porous Coordination Network
The Catalytic Z to E Isomerization of Stilbenes in a Photosensitizing Porous Coordination Network
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DOI：
10.1002/anie.201001902
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发表时间：
2010-01-01
影响因子：
16.6
通讯作者：
Fujita, Makoto
中科院分区：
文献类型：
--
作者：
Ohara, Kazuaki;Inokuma, Yasuhide;Fujita, Makoto
三（4-吡啶基）三嗪配体(1)是自组装配位笼（[1]）和配位网（[1]）的重要有机组成部分由于其刚性的平面性、三角形形状和商业可用性，配体1通常被使用，它极度缺乏电子，并且在吡啶基臂的配合下，1可以变得具有电和光化学活性。在基于三嗪的宿主中，客体与1的最低未占据分子轨道（LUMO）的相互作用有规律地产生主-客体电荷转移配合物，并且光辐射可以诱导有效的能量转移[3]，或者在某些情况下，光诱导电子转移。我们假设由1和ZnI2生成的网络2在固态下可以表现出类似的光化学反应；因此，我们研究了二苯乙烯在配位网络2中的光诱导异构化（方案1a）。包合在2孔内，(Z)-二苯乙烯在可见光照射下选择性异构化为(E)-二苯乙烯（方案1b）；在λex= 313nm处，没有得到典型的光稳态Z/E平衡比（Z/E= 92: 8）。由于客体分子可以自由地从2的孔扩散到溶液中，2的晶体有效地催化了单向的Z！二苯乙烯在环己烷中的异构化反应。本文所采用的多孔网络配合物[{(ZnI2) 3(1) 2}·x (C6H5NO2)] n （2, x% 5.5）是按照所报道的方法制备的将合成的网络2浸泡在(Z)-二苯乙烯（3a）环己烷溶液中，晶体立即由淡黄色变为亮黄色。元素分析表明，每单位含有约1个(Z)-3a分子，分子式为[{(ZnI2) 3(1) 2}·x （（Z)-3a）·y（环己烷）]n (2), x% 1.1, y% 1.0）。紫外/可见漫反射光谱在约450 nm处显示出一个新的、宽的电荷转移（CT）带。由于在配体1和(Z)-3a的甲苯溶液中没有观察到该CT带，因此1与锌（II）离子的配位和
The tris (4-pyridyl) triazine ligand (1) is an important organic building block for self-assembled coordination cages [1] and networks.[2] Typically employed because of its rigid planarity, triangular shape, and commercial availability, ligand 1 is extremely electron-deficient and, upon coordination of the pyridyl arms, 1 can become electro-and photochemically active. Guest interactions with the low-lying lowest unoccupied molecular orbital (LUMO) of 1 in triazine-based hosts regularly generate host–guest charge-transfer complexes, and photoirradiation can induce efficient energy transfer [3] or, in some cases, photoinduced electron transfer.[4]We hypothesized that network 2, which is generated from 1 and ZnI2, could display similar photochemistry in the solid state; thus we examined the photoinduced isomerization of stilbene within coordination network 2 (Scheme 1 a). Enclathrated within the pores of 2,(Z)-stilbene selectively isomerized to (E)-stilbene under visible light irradiation (Scheme 1b); the Z/E equilibrium ratio typical for the photostationary state (Z/E= 92: 8 at λex= 313nm) was not obtained. As guest molecules can freely diffuse from the pores of 2 into the solution, crystals of 2 efficiently catalyzed the one-way Z! E isomerization of stilbene in cyclohexane. The porous network complex [{(ZnI2) 3 (1) 2}· x (C6H5NO2)] n (2, x% 5.5) employed in this work was prepared according to the reported procedure.[5] When the as-synthesized network 2 was soaked in a solution of (Z)-stilbene (3a) in cyclohexane, the crystals immediately turned from pale to bright yellow. Elemental analysis showed the inclusion of approximately one molecule of (Z)-3a per unit with a formula of [{(ZnI2) 3 (1) 2}· x ((Z)-3a)· y (cyclohexane)] n (2о, x% 1.1, y% 1.0). The diffuse reflectance UV/Vis spectrum showed a new, broad charge-transfer (CT) band at approximately 450 nm. Since this CT band was not observed in a solution of ligand 1 and (Z)-3a in toluene, coordination of 1 to zinc (II) ions and