Syntheses of Dendrimer-type Model Complexes of Non-heme Enzyme Having an Ability on Alkane Oxidation

甲烷单氧合酶（MMO）是一类非血红素金属酶，因其在温和条件下对烷烃生成醇具有较高的氧合能力而备受关注。树状大分子是一种具有规则分支结构的球形单分子，类似于胶细胞，并表现出特有的行为。虽然我们已经开发出了很好的烷烃氧合催化剂，但催化体系存在催化剂仅在氯化溶剂中表现出高活性的缺陷。将树突引入到具有高烷烃氧化催化能力的钌配合物中，催化剂的溶解度可以自由控制，实现了优异的MMO模型。树枝状钌配合物已被合成。一种具有四齿配体三（吡啶基甲基）胺（TPA），另一种具有三齿配体三吡啶和双齿配体联吡啶。将苯醚型树突引入其吡啶基。制备了第一代、第二代和第三代树状大分子，发现它们对烷烃氧合具有催化能力。在目前的催化剂中，假设关键中间体是五配位的物质。一般来说，钌配合物具有光化学活性，如在辐照下解离机制下的异构化和/或配体取代。初步实验表明，制备的钌配合物具有光化学异构化和/或配体取代活性，量子产率良好。此外，在氯化溶剂中辐照时，还观察到可能的五配位种的形成。五配位中间体与吡啶n -氧化物反应得到了与文献报道的氧化铕配合物具有相似紫外光谱的新产物。进一步的研究正在进行中。

Methanemonooxygenase (MMO), one of the Non-heme metalloenzyme, draws much attention due to its high ability on oxygenation of alkanes giving alcohols under mild conditions. Dendrimers having a structure with regularly branching form are spherical single molecular, which resembles to micells, and show characteristic behavior. Although we have already developed good catalysts for alkane oxygenations, the catalytic system had a defect that the catalysts showed high activity only in chlorinated solvents. Introducing dendrons to our ruthenium complexes having high catalytic ability on alkane oxygenation, the solubility of the catalyst is able to be freely controlled and realizes excellent models of MMO.Dendrimer-type ruthenium complexes have been synthesized. One has tetradentate ligand, tris (pyridylmethyl) amine (TPA), and the other has both terdentate ligand, terpyridine, and, bidentate ligand, bipyridine. Dendrons of benzylether type were introduced to their pyridyl groups. First, second, and third generation of the dendrimers were prepared and it was found that they have catalytic ability on alkane oxygenation.In the present catalysts the key inetermediate is assumed to be a five-coordinated species. In general, ruthenium complexes are known to show photochemical activity such as isomerization and/or ligand substitution under irradiation with dissociative mechanism. Preliminary experiments revealed that the ruthenium complexes prepared above showed an activity on photochemical isomerization and/or ligand substitution with good quantum yield.Further, formation of possible five-coordinated species was observed on irradiation of the complexes in chlorinated solvent. The reaction of the five-coordinated intermediate and pyridine N-oxide gave new spieces showing similar UV spectra to those of oxoruthenium complexes reported in literatures. Further studies are in progress.