单核铁(Ⅲ)双卟啉配合物在溶液中的构象平衡及其对环己烷羟化反应的催化活性的影响

Conformation Equilibrium of Iron(Ⅲ) metal free Porphyrin Dimers and Its Effect on Catalytic Activity for Cyclohexane Hydroxylation

合成及表征了一系列以柔韧碳氢链相连不同长度的ｐ／ｐ型单核铁（Ⅲ）双卟啉配合物，以可见光谱首次观察到该系列配合物在氯仿溶液中开放式及闭合式构象的平衡，发现６８０ｎｍ处吸收峰强度与这种构象平衡有关，烷氧链越长，该吸收峰强度越大．利用该类配合物模拟了细胞色素Ｐ４５０单加氧酶对环己烷的羟化作用，催化结果表明，在以分子氧为氧源及还原剂存在的温和条件下，该类配合物的催化活性显著高于单核铁卟啉（ＦｅＴＰＰＣｌ），随着柔韧碳氢链长度的增加，双卟啉的催化活性依次增加．高的催化活性与双卟啉配合物在溶液中的构象平衡，即闭合式构象引起的立体位阻及电子转移有关．

A series of iron(Ⅲ) metal free porphyrin dimers covalently linked with -O(CH 2) n O- chain( n =2～5) have been synthesized and characterized. By using UV Visible spectra, an equilibrium of two different conformations of porphyrin dimers, open and closed, in chloroform solution has been observed for the first time. The intensity of adsorption band 680 nm may be related to the conformation equilibrium, the longer the length of the alkoxy chain, the stronger the intensity of band 680 nm is present. As a new model catalytic system of cytochrome P450, all these dimers have higher catalytic activities than the corresponding mono iron(Ⅲ) porphyrin, and their catalytic activities increase gradually with the increase of the length of flexible chain. The higher catalytic activities may be related to the steric hindrance and intramolecular electron transfer of the porphyrin dimers caused by the conformation equilibrium.