预组织特性配体的设计合成及其对放氧复合物OEC的仿生学研究

认识光合系统II(Photosystem II, PSII)中放氧复合物(Oxygen-Evolving Complex, OEC)的水氧化机理以及通过仿生学途径研发功能与其类似的小分子器件，可以为替代化石燃料的清洁能源的发展提供一个新的选择，是人工光合作用的一个重要追求目标。本项目着重于模拟天然金属酶预组织多肽骨架对核心金属簇活性的调控作用，设计与合成一系列C3对称的以三蝶烯为核心的预组织多齿配体。研究该配体对OEC的杂核[Mn4CaO5]簇的仿生学促进机制，提出以递进的方式，逐步构建起从立方同核[Mn4O4]簇到立方杂核[Mn3CaO4]簇直至非对称的[Mn4CaO5]簇体系，从而实现对OEC核心锰簇的几何结构的可控调制。以此类预组织配体得到的杂核锰钙簇配合物为平台，研究其在高氧化态下O-O键生成机理及氧转移过程，并最终获得高活性的水氧化。

Understanding the water oxidation mechanism within the oxygen-evolving complex (OEC) of photosystem II (PSII) as well as developing functional small-molecular machine via biomimetic modeling can provide a unique option towards clean and environmentally benign energy source over fossil fuels, which are essential components in artificial photosynthesis. Our proposal focuses on mimicking the preorganization character of the polypeptide framework in natural metalloenzyme as well as its ability in tuning the chemical behavior and reactivity of the metallic core. A series of preorganized, C3-symmetric, polydentate ligands based on unprecedented triptycene backbone are designed and will be synthesized in this project. Towards our goal in the modeling of the [Mn4CaO5] core of OEC, our strategy is to gradually construct manganese clusters from homonuclear cubic [Mn4O4] to heteronuclear cubic [Mn3CaO4], until unsymmetrical [Mn4CaO5] cluster. With the successful employment of this controllable fashion, we wish to eventually replicate the topological structure of the OEC metallic core. Along with our modeling study, we will also use the obtained manganese-calcium clusters as structurally stable platforms in the study of O-O bond formation mechanism as well as oxygen transfer process under oxidative environment. Eventually, we wish to achieve high efficient water oxidation catalysis via this novel biomimetic approach.