Models of the Photosynthetic Oxygen-Evolving Complex

在化学部化学催化计划资助的这个项目中，佛罗里达大学的乔治·克里斯托教授合成并研究了与放氧复合物（OEC）有关的化合物。OEC存在于植物和某些细菌中，25亿多年来一直利用阳光作为能源将水转化为氧气。因此，OEC负责生产和维持所有呼吸生命所依赖的大气氧气。OEC太脆弱，无法从天然来源中分离出来;因此研究人员正在寻求在实验室中合成OEC，以研究其特性以及如何制造氧气。Christou实验室将合成OEC的模型化合物，并研究它们催化水转化为氧气的能力。这项研究对目前利用和储存太阳能的努力产生了更广泛的影响。它还为研究生创造了获得合成和专门技术（如水氧化的磁化学和电催化）高级培训的机会。 研究的目标是合成和研究Mn 4Ca/氧簇作为模型的OEC，使用最近开发的方法，使混合Mn/Ca立方烷化合物。将合成具有螯合物诱导的、模拟肽支架对OEC的作用的结构扰动的衍生物，以及具有不同氧化态的锰和具有锶而不是钙的衍生物，Sr是可以在OEC中取代Ca并保留显著活性的唯一金属。通过磁性测量，并通过EPR和X-射线光谱的化合物的表征将提供在OEC的研究中有用的基准。拟议中的工作将使测试目前的假设的精确水平的OEC的结构畸变和其对OEC的性能的影响，有关是否Sr取代的OEC是isostructural与钙的形式，以及有关的起源的明显不同的，电子性能的OEC在一个给定的氧化水平，并取决于生成条件。OEC模型和其他合成Mn化合物也将被探索作为功能模型，即作为水氧化为氧气的电催化剂，建立在发现某些Mn羧酸盐簇具有低过电位的活性的基础上。

In this project funded by the Chemical Catalysis Program of the Chemistry Division, Professor George Christou of the University of Florida synthesizes and studies compounds related to the oxygen-evolving complex (OEC). The OEC is found in plants and certain bacteria, and for over 2½ billion years has been converting water to oxygen gas using sunlight as an energy source. Hence the OEC is responsible for the production and maintenance of the atmospheric oxygen on which all respiring life depends. The OEC is too fragile to be isolated from natural sources; therefore researchers are seeking to synthesize the OEC in the laboratory to study its properties and how it makes oxygen. The Christou lab will synthesize model compounds for OEC and study their ability to catalyze conversion of water to oxygen. This research has broader impacts on current efforts to harness and store solar energy. It also creates opportunities for graduate students to acquire advanced training in synthesis and specialized techniques such as magnetochemistry and electrocatalysis of water oxidation. The goal of the research is to synthesize and study Mn4Ca/oxo clusters as models of the OEC, using recently developed methodologies to make mixed Mn/Ca cubane compounds. Derivatives with chelate-induced, structural perturbations that mimic the effect of the peptide scaffold on the OEC will be synthesized, as will be derivatives with manganese in different oxidation states and with strontium instead of calcium, Sr being the only metal that can replace Ca in OEC with retention of significant activity. The characterization of the compounds by magnetic measurements, and by EPR and X-ray spectroscopy will provide benchmarks useful in the study of OEC. The proposed work will enable the testing of current hypotheses about the precise level of structural distortion of the OEC and its influence on the properties of OEC, about whether the Sr-substituted OEC is isostructural with the Ca form, and about the origin of the distinctly different, electronic properties of the OEC at a given oxidation level and depending on generation conditions. The OEC models and other synthetic Mn compounds will also be explored as functional models, namely as electrocatalysts for water oxidation to oxygen, building on the discovery of such activity with low overpotential by certain Mn carboxylate clusters.