Nanochannel-promoted polymerization of substituted acetylenes in porous coordination polymers.
Nanochannel-promoted polymerization of substituted acetylenes in porous coordination polymers.
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DOI：
10.1002/anie.200600333
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发表时间：
2006-06
影响因子：
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通讯作者：
T. Uemura;R. Kitaura;Y. Ohta;M. Nagaoka;S. Kitagawa
中科院分区：
文献类型：
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作者：
T. Uemura;R. Kitaura;Y. Ohta;M. Nagaoka;S. Kitagawa
聚（取代乙炔）的电子和光学性质也受到了广泛的关注，如导电材料，非线性光学，聚合物传感器和分子电子学中的组件。[4]特别是，通过使用几种类型的催化剂，为了提高催化剂的活性，减少环状三聚体副产物的生成，（取代的苯），并控制立体结构（顺式和反式链序列），因为聚乙烯的特性（取代的乙炔），如共轭长度，超结构和加工性，可以通过改变取代基和立构规整性进行精确调节。[4，5]此外，基于这种π-共轭聚合物的定义明确的纳米结构的设计和理解是当代聚合物和固态科学中最具挑战性的目标之一，因为它们未来将应用于创建基于纳米分子的器件。[6]最近，我们首次展示了PCP纳米通道作为聚合领域的用途，[7]这不仅导致了受控反应，而且还导致了纳米通道结构中有序的单一聚合物链的新模型系统。[8]在本研究中，我们在[Cu 2（pzdc）2（L）] n的一维特定纳米通道中进行了取代乙炔的可控和选择性聚合（1个; pzdc=吡嗪-2，3-二羧酸酯，L=柱配体）[2b，9]，其中碱性羧酸酯氧原子作为孔壁上的催化相互作用位点。（吡嗪）] n（1a），与一维通道（4.0 6.0 2）具有基本的表面氧原子作为特定的吸附位点乙炔分子（HC CH），作为一个结果的双氢键相互作用。[2b]HC CH分子被牢固地固定在1a（1a'HC CH）的受限纳米通道中，这导致HC CH分子的氢原子与羧酸根氧原子之间的电子离域。[2b]此外，与金属氧化物通常的情况一样，即使在室温下，在固体表面的这种刘易斯碱位点上也已经实现了每个HC CH分子提取一个质子。[10]这些事实启发我们假设，在1的通道中引入更多的单取代乙炔（即带有吸电子取代基的乙炔）将通过C3 OH键解离产生反应性乙炔化物物种，这将随后引发取代乙炔的阴离子聚合。此外，窄的纳米通道结构将引导选择性朝向具有反式加成的聚合，因为对于形成三取代苯和顺式聚合物的禁止性空间需求。因此，我们进行了甲基丙炔酸酯（MP）的聚合在纳米通道[Cu 2（pzdc）2（4，4 '-bipyridine）] n（1b;通道尺寸8.2 6.0 2）。在本实验中，纯MP与天蓝色配合物1b在室温下反应12小时，得到深绿色粉末复合物（1b'polyMP）。[11]在1b'polyMP的固态UV/维斯反射光谱中，在450 nm附近存在额外的吸收，这可归因于π共轭polyMP（图1a）。的
Much attention has also been directed to the electronic and optical properties of poly (substituted acetylenes) for a wide range of applications such as conducting materials, nonlinear optics, polymer sensors, and components in molecular electronics.[4] In particular, the controlled polymerization of substituted acetylenes by using several types of catalysts (such as metal complexes, anions, cations, radicals) has been investigated with the aim of increasing catalytic activity, decreasing the formation of cyclic trimer by-products (substituted benzenes), and controlling the stereostructure (the cis and trans chain sequence) because the characteristic properties of poly (substituted acetylenes), such as conjugation length, supra-structures, and processability, can be precisely adjusted by changing the substituents and stereoregularity.[4, 5] In addition, the design and understanding of well-defined nanostructures based on such π-conjugated polymers is one of the most challenging goals in contemporary polymer and solid-state sciences for their future application in the creation of nanosized molecule-based devices.[6] Recently, we first demonstrated the use of PCP nanochannels as a field of polymerization,[7] which lead not only to a controlled reaction but also to new model systems for wellordered single polymer chains in the nanochannel structures.[8] In this study, we have performed controlled and selective polymerizations of substituted acetylenes in onedimensional specific nanochannels of [Cu2 (pzdc) 2 (L)] n (1; pzdc= pyrazine-2, 3-dicarboxylate, L= pillar ligands)[2b, 9] with basic carboxylate oxygen atoms as catalytic interaction sites on the pore walls.A pillared-layer microporous compound,[Cu2 (pzdc) 2-(pyrazine)] n (1a), with one-dimensional channels (4.0 6.0 2) has basic surface oxygen atoms that act as specific adsorption sites for acetylene molecules (HC CH), as a consequence of a double hydrogen-bonding interaction.[2b] The HC CH molecule is strongly fixed in the confined nanochannel of 1a (1a'HC CH), which results in electron delocalization between the hydrogen atoms of the HC CH molecule and the carboxylate oxygen atoms.[2b] In addition, as is often the case with metal oxides, abstraction of one proton per HC CH molecule has been realized on such Lewis base sites of solid surfaces, even at room temperature.[10] These facts inspired us to postulate that the introduction of moreacidic monosubstituted acetylenes (ie, acetylenes bearing an electron-withdrawing substitution group) in the channels of 1 would produce reactive acetylide species by CÀH bond dissociation, which would subsequently initiate anionic polymerization of the substituted acetylenes. Moreover, the narrow nanochannel structure would direct the selectivity towards a polymerization with trans addition because of the prohibitive steric demand for the formation of trisubstituted benzenes and cis polymers. Thus, we carried out the polymerization of methyl propiolate (MP) in the nanochannel of [Cu2 (pzdc) 2 (4, 4’-bipyridine)] n (1b; channel size 8.2 6.0 2). In this experiment, the reaction of neat MP with the sky-blue complex 1b for 12h at room temperature provided a dark-green powder composite (1b'polyMP).[11] In the solid-state UV/Vis reflection spectrum of 1b'polyMP there is an additional absorption around 450 nm, which can be attributed to the π-conjugated polyMP (Figure1a). The