Fine Tuning of Structure and Reactivity of Dinuclear Transition Metal Active Oxygen Complexes

本研究对双核过渡金属-活性氧配合物的结构、物化性质和反应活性进行了系统的研究，旨在揭示生物体系中氧的活化机理以及催化氧化反应的机理。研究结果如下：(1)研究了一系列双齿、三齿和四齿胺类配体与分子氧的反应，探讨了配体对活性氧中间体结构和物化性质的影响。(2)首次发现了(μ-η^2：η^2-Peroxo)双铜(II)配合物定量氧化苯酚为邻苯二酚。详细的机理研究，包括动力学和产物分析表明，(μ-η^2：η^2-Peroxo)二铜(II)络合物将酚类化合物氧化成儿茶酚的过程是通过过氧基对苯酚…的亲电攻击进行的在过氧基中间体和底物之间的二元络合物中有更多的TE环，为了解酪氨酸酶的酚酶活性提供了有价值的信息。(3)详细研究了由(μ^2：μ-η^2-Peroxo)二铜(II)络合物通过O-O键均裂得到的双(η^2：η^2-过氧基铜)络合物的形成机理和反应活性。研究发现，双(μ-氧代)二铜(III)络合物的分解导致分子内脂肪族配体羟化反应。在10-甲基-9，10-二氢吖啶(AcrH_2)和1，4-环己二烯(CHD)等外部底物与吡啶乙胺双齿配体负载的双(μ-氧代)二铜(III)配合物的C-H键活化中，形成新的铜-活性氧中间体，如(μ-氧代)(μ-氧基)二铜(III)，(4)首次系统地研究了一系列双[2-(2-吡啶)乙基]胺配体负载的双(μ-氧)镍(III)配合物的光谱特征、形成机理和反应活性，以进一步揭示非血红素过渡金属配合物活化氧的机理。(5)在铜离子与结构相关的三种含二硫基的二核配体的反应中，得到了三种不同类型的双核铜配合物。配合物的晶体结构表明，三个配合物中有两个是保留了母体配体的二硫键的二铜(I)，但二硫键对两个铜离子的配位方式明显不同。与这些配合物相比，第三个配合物中含有一个双(μ-硫代)二铜(II)核，它被认为是细胞色素C氧化酶(CCO)和一氧化二氮还原酶(NOR)铜A电子转移中心的良好模型。较少

In this research project, structure, physicochemical property, and reactivity of dinuclear transition metal-active oxygen complexes have been systematically investigated in order to shed light on the dioxygen activation mechanism in not only biological systems but also catalytic oxygenation reactions. Followings are summary of the results.(1) Reactions of Cu (I) complexes supported by a series of bidentate, tridentate, and tetradentate amine ligands with molecular oxygen have been investigated to explore the ligand effects on the structure and physicochemical properties of the active oxygen intermediates.(2) Quantitative oxygenation of phenols to catechols by a (μ-η^2 : η^2-peroxo) dicopper (II) complex have been found for the first time. Detailed mechanistic studies including kinetics and product analysis implicated that the oxygenation of phenolates to catechols by the (μ-η^2 : η^2-peroxo) dicopper (II) complex proceeds via an electrophilic attack of the peroxo species to the phenola … More te ring in a binary complex between the peroxo intermediate and the substrate, providing valuable insight into phenolase activity of tyrosinase.(3) Formation mechanism and reactivity of a bis (μ-oxo) dicopper (III) complex that could be derived from a (μ-η^2 : η^2-peroxo) dicopper (II) complex via the O-O bond homolysis have been investigated in detail. It has been found that the bis (μ-oxo) dicopper (III) complex decomposes leading to intramolecular aliphatic ligand hydroxylation reaction. In the C-H bond activation of external substrates such as 10-methyl-9, 10-dihydroacridine (AcrH_2) and 1, 4-cyclohexadiene (CHD) with the bis (μ-oxo) dicopper (III) complex supported by a pyridylethylamine bidentate ligand, formation of a new copper-active oxygen intermediate, such as (μ-oxo)(μ-oxyl radical) dicopper (III), has been implicated as an actual reactive species for hydrogen atom abstraction from the substrates.(4) The first systematic studies on spectroscopic features and the formation mechanism as well as the reactivity of the bis (μ-oxo) dinickel (III) complexes supported by a series of bis [2-(2-pyridyl) ethyl] amine ligands have been carried out in order to shed light further on the dioxygen activation mechanism by non-heme transition-metal complexes.(5) Three different types of dinuclear copper complexes have been obtained in the reactions of cuprous ions and structurally related three dinucleating ligands containing a disulfide group in it. The crystal structures of the complexes reveal that two of the three complexes are dicopper (I) retaining the disulfide group of the parent ligands, but that the coordination mode of the disulfide group to the two cuprous ions are significantly different. In contrast to those complexes, the third one has a bis (μ-thiolato) dicopper (II) core in it which is regarded as a good model of the Cu_A electron-transfer site of cytochrome c oxidase (CcO) and nitrous oxide reductase (NOR). Less