Chemistry of Macrocyclic Polyamine Complexes

该有机和大分子化学项目资助了Cynthia Burrows教授的研究，旨在表征质子化大环多胺的结合和催化特性。这项工作属于“主客”化学的一般领域，并构成了人工化学系统中酶结合和催化复制的“仿生”方法。大环多胺可以参与阳离子和阴离子络合现象。18元环大小的四胺在水介质中易于四质子化，其高正电荷密度使其能够与各种有机和无机阴离子形成强缔合配合物。在这种情况下，Burrows小组将研究具有官能化侧链的光学活性大环精胺类似物。磷酸酯和羧酸盐将在各种介质中进行研究，以确定强关联的重要参数。含有咪唑基团的大环被设计为磷酸酯水解的潜在催化剂。十四元环大小的四胺与过渡金属阳离子形成稳定的配合物，尤其是二价钴、镍和铜离子。像卟啉一样，环胞体稳定某些金属的高氧化态。Burrows最近发现了第一个镍催化的烯烃环氧化反应，其中环环环是镍（III）氧化态可及性的关键。为了进一步改变金属的反应性和研究烯烃不对称环氧化的可能性，目前正在研究带有垂坠连接基团的光学活性旋环。这些研究将加深对分子识别复合物和催化的分子间相互作用的理解。

This grant in the Organic and Macromolecular Chemistry Program supports research by Prof. Cynthia Burrows, which is aimed at characterizing the binding and catalytic properties of protonated macrocyclic polyamines. This work falls in the general area of "host- guest" chemistry and constitutes a "biomimetic" approach to replication of enzyme binding and catalysis in man-made chemical systems. Macrocyclic polyamines can participate in both cation and anion complexation phenomena. Tetraamines of 18-membered ring size are easily tetra-protonated in aqueous media, and their high positive charge density accounts for their ability to form strong association complexes with various organic and inorganic anions. In this context, the Burrows group will investigate optically active macrocyclic spermine analogs which possess functionalized side chains. Phosphate esters and carboxylates will be studied in various media in order to define the parameters important for strong association. Macrocycles bearing a pendant imidazole group have been designed as potential catalysts for phophate ester hydrolysis. Tetraamines of 14-membered ring size (cyclams) form stable complexes with transition metal cations, especially divalent cobalt, nickel, and copper ions. Like porphyrins, the cyclams stabilize high oxidation states of certain metals. Burrows has recently discovered the first nickel-catalyzed olefin epoxidations in which cyclam is the key to accessibility of the Nickel(III) oxidation state. Optically active cyclams bearing pendant ligating groups are under study in order to further modify the reactivity of the metal and to investigate the potential for asymmetric epoxidation of olefins. These studies will enhance understanding of intermolecular interactions in molecular recognition complexes and catalysis.