Polynuclear Clusters in Biology - Structure, Reactivity

生物体中各种底物的氧化和还原对于维持生命的过程至关重要。多电子转移过程虽然在性质上不太频繁，但也同样重要。后者包括：氮气在固氮酶中的6E-还原为氨，亚硫酸盐和亚硝酸盐还原酶中亚硫酸盐的6E-还原为硫化物和亚硝酸盐为氨，以及光合作用中2H20的4E-氧化为O2。这项建议涉及a)参与多电子还原的金属酶和b)活跃在氧化过程中的非卟啉、非铁/S铁中心的合成类似物的合成和研究。具体地说：Fe/M/S(M=Mo，V)的合成、结构、光谱性质和反应活性。Fe/M/S团簇有望作为Fe/M/S中心的合成类似物出现在固氮酶和替代钼的含钒或铁的交替固氮酶中。将要合成的新型Fe/S簇合物被设计为固氮酶P-簇合物的模型。合成了含有pi受体配体的Fe/S簇合物的超分子组装，并研究了它们在双金属活化和催化还原氮气中的可能作用。第一排元素的多核、混合配体、羧酸盐-儿茶酚络合物将作为催化各种底物多电子氧化的酶中活性中心的结构和反应模型进行研究。这些化合物中的儿茶酚配体作为氧化等价物的存储位置的功能将被确定。

The oxidation and reduction of various substrates in living organisms are of fundamental importance to life sustaining processes. Multi-electron transfer processes, although less frequent in nature are of equally great importance. Included among the latter are: the 6e-reduction of N2 to ammonia in nitrogenase, the 6e-reduction of sulfite to sulfide and of nitrite to ammonia in sulfite and nitrite reductases respective And the 4e- oxidation of 2H20 to O2 in photosynthesis. This proposal is concerned with the synthesis and study of synthetic analogs for a) metalloenzymes involved in multi-electron reduction and b) the non-porphyrin, non-Fe/S, iron centers active in oxidation processes. Specifically,: the synthesis, structures, spectroscopic properties and reactivitys of Fe/M/S (M=Mo,V) proposal. The Fe/M/S clusters are expected to sere as synthetic analogs for the Fe/M/S centers in the nitrogenases and alternate nitrogenases that contain vanadium or iron in place of molybdenum. The new types of Fe/S clusters that will be synthesized are designed as models for the P- clusters of nitrogenase. Superamolecular assemblies with attended Fe/S clusters containing pi acceptor ligands will be synthesized., and their possible function in the bimetallic activation and catalytic reduction of dinitrogen will be investigated. Multi-nuclear, mixed-ligand, carboxylate-catecholate complexes of first row elements will be studied as structure and reactivity models for the active sites in enzymes that catalyze the multi-electron oxidation of various substrates. The function of the catecholate ligands in these compounds, as storage sites of oxidizing equivalents, will be determined.