Development of cryptand molecules of multiple ligation with allosteric binding behavior

这项工作旨在了解隐体样卟啉的新结合模式的机制方面，以及实现变构结合的结构因素。制备了一系列由6个吡咯和3个六元杂芳香化合物组成的隐状卟啉类化合物，并研究了它们与客体分子的多重结合行为。含有3个和2个吡啶的隐基分别与3个和2个羧酸结合，在CH_2Cl_2中滴定实验，观察到理想的正同向变构结合行为。在乙腈中观察到1 - 1或1 - 2主客体比的中间配合物，表明基于多个氢键的变构结合在极性溶剂中是不利的。在吡咯上含有不同空间体积的烷基取代基的三个密码基。-位用于研究醇的结合行为。紫外-核磁共振实验表明，CDCl_3的干溶液具有正变构结合行为。在吡啶旁边有一个庞大的异丁基取代基，增加了平衡常数。在桥头堡加入氰基取代基的隐体极大地提高了隐体样卟啉类化合物的稳定性，扩大了其变构结合的范围。

This work aimed at understanding the mechanistic aspect in the novel binding mode of cryptand-like porphyrinoids and also the structural factors that enables allosteric binding. A number of the cryptand-like porphyrinoids made of six pyrroles and three six-membered(hetero) aromatics were prepared and their multiple binding behavior of guest molecules was investigated. The cryptands containing three and two pyridines bind three and two carboxylic acids, respectively, where ideal positive homotropic allosteric binding behavior was observed through the titration experiments in CH_2Cl_2. The intermediate complexes of a one-to-one or a one-to-two host-guest ratio were observed in acetonitrile to show that allosteric binding based on multiple hydrogen bondings is unfavorable in polar solvents. Three cryptands containing alkyl substituents of a different steric bulk at the pyrrole.-positions were used to study binding behavior of alcohols. VT-NMR experiments on the dry CDCl_3 solution of a mixture of cryptand and alcohol revealed positive allosteric binding behavior. A bulky iso-butyl substituent next to the pyridine increased equilibrium constants. Cryptand with the cyano substituents at the bridgehead greatly improved the stability of the cryptand-like porphyrinoid, which expands the scope of allosteric binding.