多孔手性三齿羧酸配位聚合物的制备及催化性能的研究

The design and synthesis of chiral coordination polymers (CCPs) have been extensively studied in recent years, not only because of their intriguing topological structure, but also due to their potential properties in chiral catalysis. In this proposal, four series of eight novel tridentate chiral carboxylic acid ligands are planned to be synthesized, based on which, a series of CCPs could be constructed by the methods of crystal engineering. The chiral ligands proposed in this project have a configuration with separated "twigs". Such configuration is prone to form CCPs with open pores more easily than linear ligands. This project intends to study the effects of reaction conditions on the size and structure of the pores of CCPs and their catalytic properties. The structures of the CCPs constructed by the ligands with different linkers are also going to be compared and investigated, such as O atom acting as a linker in the ligand of L1a and –NH group as a linker in L1b. Based on the relationship and difference of the ligands, the chiral catalytic mechanisms of these CCPs are also planned to be discussed. This project would provide valuable experimental data for the investigation of porous CCPs construction and their chiral catalytic properties.

近年来，有关手性配位聚合物（Chiral Coordination Polymers，CCPs）的设计和合成的研究发展迅速。这是因为CCPs不仅具有优美的拓扑结构，又具有潜在的手性催化性能。本项目拟合成四系列八种新颖的三齿手性羧酸配体，并按照晶体工程学的研究方法制备系列CCPs。本项目所设计的手性配体分子具有分开的“枝杈”状构型，研究表明此种结构特征较常见的线性分子更易构筑具有开放孔道的配位聚合物。本项目拟研究反应条件对CCPs孔道结构的影响，并研究此系列CCPs的手性催化性能。探讨含有O原子的L1a配体分子与含有-NH基团的L1b在构筑CCPs时的区别及联系，并利这两种配体的相关性，研究它们所构成的CCPs的手性催化模式和机理。本项目将对具有开放孔道的CCPs的构筑及其催化性能的研究提供有价值的实验数据。

本项目设计并合成了2个系列总计5对不同的手性三齿羧酸类配体，所有配体的结构通过核磁共振氢谱、红外光谱、CD谱图及X-光单晶衍射等方法得以确认。将上述配体分别同稀土、过渡金属离子作用，获得了近60个手性配位聚合物及其单晶，所有手性配位聚合物的结构均经X-光单晶衍射法得以表征和确认。发现含氮类化合物作为辅助配体可以对所构筑的手性配合物的结构进行调节，辅配体的长度对手性配位聚合物的结构具有一定的影响。以不对称Henry反应、羟醛缩合反应及硫醚氧化反应作为参照反应，考察了上述手性配合物的不对称催化活性。发现某些手性配位聚合物对不同尺寸和空阻的底物分子具有一定的选择性，对不同尺寸的反应底物具有选择性，从而产生立体选择性。通过对产物的ee值测试发现，某些手性配位聚合物对某类不对称反应展现非常好的催化活性，其对映体过量值可高达98%。催化剂重复性研究发现当催化剂循环5次后的收率和ee值没有发生明显的变化。粉末X-光衍射分析结果同时也表明，配合物在催化反应后，骨架结构并未发生很明显的变化，说明该类配合物可用作有前途的不对称合成催化剂使用。同时对合成获得的手性配位聚合物的光学性质进行了研究，发现大多数手性配位聚合物展现不同强度的二阶非线性光学活性，表明该类化合物也可能成为潜在的光学材料应用。