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

本课题对双核过渡金属-活性氧配合物的结构、理化性质和反应活性进行了系统的研究，旨在揭示生物体系和催化氧化反应中的双氧活化机理。以下是对结果的总结。(1)研究了一系列双齿、三齿和四齿胺配体负载的Cu (I)配合物与分子氧的反应，探讨了配体对活性氧中间体结构和理化性质的影响。(2)首次发现了（μ-η^2: η^2-过氧）二铜络合物对酚类化合物与儿茶酚的定量氧化反应。包括动力学和产物分析在内的详细机理研究表明，（μ-η^2: η^2-过氧）二铜（II）配合物通过过氧物质对苯酚的亲电攻击将酚类化合物氧合为儿茶酚。更多的环在过氧中间体和底物之间的二元配合物中，为酪氨酸酶的酚酶活性提供了宝贵的见解。(3)详细研究了由（μ-η^2: η^2-过氧）diccopper （II）配合物经O-O键均解得到的双（μ-氧）diccopper （III）配合物的形成机理和反应活性。研究发现，双（μ-氧）二铜（III）配合物的分解引起分子内脂族配体羟基化反应。在外部底物如10-甲基- 9,10 -二氢吖啶（AcrH_2）和1,4 -环己二烯（CHD）与吡啶乙胺双齿配体负载的双（μ-氧）二铜（III）配合物的C-H键活化过程中，一种新的铜-活性氧中间体如（μ-氧）（μ-氧自由基）二铜（III）的形成被认为是从底物中提取氢原子的实际反应物质。(4)首次系统地研究了一系列双[2-（2-吡啶基）乙基]胺配体负载的双（μ-氧）二镍（III）配合物的光谱特征、形成机理和反应活性，以期进一步阐明非血红素过渡金属配合物的双氧活化机理。(5)铜离子与结构相关的含二硫基的三种双核配体反应，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，三种配合物中有两种都是二铜(I)，保留了母体配体的二硫化物基团，但二硫化物基团与两种亚铜离子的配位方式有显著差异。与这两种配合物相比，第三种配合物具有双（μ-硫代）二铜（II）核，被认为是细胞色素c氧化酶（CcO）和氧化亚氮还原酶（NOR）的Cu_A电子转移位点的良好模型。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