【作者】 孙洪飞；

【导师】 孙立成； 王梅；

【作者基本信息】 大连理工大学 ， 应用化学， 2008， 博士

【摘要】 非血红素铁氧化酶的化学模拟是近年来生物无机化学领域的研究热点之一。近年来随着生物技术、各种光谱手段及晶体学的发展,已解析出多种非血红素铁氧化酶活性中心的晶体结构。在这些结构中,都存在组氨酸,其中的咪唑环与铁配位。由此可见咪唑环类配体在非血红素铁氧化酶体系中的重要作用。迄今对非血红素铁氧化酶活性中心结构的化学模拟大多选择非环状的N₄配体与铁配位,其中吡啶环类配体广泛被应用。此外由于非血红素铁氧化酶能够利用分子氧或H₂O₂等“绿色”氧化剂,在温和条件下高效高选择性地催化烷烃、烯烃和酚等众多有机底物的氧化反应,这对于开发绿色环保氧化工艺具有重要意义。基于以上的研究背景,本论文采用含咪唑环类非环状N₄配体对非血红素铁氧化酶的活性中心进行了化学模拟,对配体进行化学修饰,设计合成了一系列非血红素铁氧化酶模型配合物,并研究了铁配合物对环己烷、环己烯、乙苯、苯乙烯、1-辛烯及金刚烷的催化氧化活性和选择性。所得模型配合物的晶体结构表明,模型配合物都具有六配位八面体构型,催化数据显示该类配合物对有机底物催化活性中等,催化结果低于同类含TPA（TPA=tris（2-pyridylmethyl）amine）配体的模型配合物。其中配合物[FeL⁴Cl₂]（ClO₄）（Fe4a,L⁴=N,N-二（2-吡啶甲基）-N-（2-苯并咪唑甲基）胺）显示了较高的活性和选择性,以H₂O₂为氧化剂氧化环己烯的转化率达到83.8%,以^tBuOOH（过氧叔丁醇）为氧化剂氧化金刚烷的3°/2°达到19.9,表明在以上体系中高价态铁氧中间体为主要氧化物种。综上,苯并咪唑类配体的引入使其在非血红素铁氧化酶活性中心结构模拟上与天然酶更为接近,但是其仿生催化效果却不十分理想。利用所得的模型配合物[Ru（L⁴）（BPY）]（PF₆）₂（Ru4a）和[Ru（L⁴-H）（BPY）]（PF₆）（Ru4b）,我们进一步研究了质子偶合电子转移反应,构建了一个质子偶合电子转移模型。NMR和MS研究发现,配体L⁴中的N-H键的质子可以发生可逆的去质子化/质子化反应,并且在此过程中配合物结构没有改变。通过CV研究发现,中心金属Ru（Ⅱ/Ⅲ）的氧化还原电位从0.69V降低到0.26V,Pourbaix曲线的斜率为53.6（接近59）,因此该质子偶合的氧化还原过程中包含一个电子与一个质子。此外,对质子偶合电子转移反应的动力学进行了初探,光谱电化学的研究结果表明可以采用闪光光解的方法来研究此模型的动力学;配合物Ru4a对光敏剂Ru（BPY）₃（PF₆）₂有明显的淬灭作用。更多还原

【Abstract】 In the past decade, the research on non-heme iron oxygenases has emerged as a hot project in bioinorganic field. Several crystal structures of non-heme iron oxygenases were determined with the development of biology techniques, various spectroscopic techniques and crystallography. Crystal structure revealed that imidazole in histidine coordinates to the non-heme oxygenase active site in all proteins, which shows the ligands containing imidazole unit are important in non-heme iron oxygenases. Many non-ringed N₄ ligands were used in functional synthetic models, especially the ligands containing a pyridine moiety. Under mild conditions, the bio-inspired catalysts based on non-heme iron oxygenases can selectively and efficiently catalyze oxidation reactions of a large range of substrates such as alkanes, alkenes and phenols by using "green" oxidants. It may give a promising way to substitute present oxidation processes.Encouraged by these achievments, in this thesis, the work is focused on mimicking the structre of non-heme iron oxygenases using the N₄ ligands with benzimidazole unit. A series of iron complexes were synthesized as functional models of non-heme iron oxygenases, their catalytic properties for the oxidation of hydrocarbons were investigated. Crystal structures showed that all iron centers contain a distorted octahedral coordination gemometry. Catalytic results indicated that the activity of model complexes was lower than the iron complexes containing TPA （TPA = tris（2-pyridylmethyl）amine） . Fe4a exhibited high activities（83.8%） and high regioselectivities（3°/2°= 19.9）. The model complex structures are close to the active site of natural enzymes, but catalytic results were not satisfactory.Proton coupled electron transfer （PCET） reaction was also investigated using the model complexes Ru4a and Ru4b, and a proton coupled electron transfer model was created. The NH group of the ligand L⁴ readily undergoes a reversible protonation/deprotonation process, which is confirmed by spectroscopic and electrochemical evidences. The reversible protonation/deprotonation regulates the oxidation potential of the Ru^Ⅱ/Ru^Ⅲredox couple in the range of 430 mV without changing the framework of the ruthenium complex. The kinetics of the PCET was also investigated by spectroelectrochemistry and flash photolysis spectrophotometer, but Ru4a quenched the exited state of Ru（BPY）₃（PF₆）₂.更多还原