Polynuclear Clusters in Biology - Structure, Reactivity

生物体中各种基质的氧化和还原对生命维持过程至关重要。多电子转移过程虽然在自然界中不太频繁，但同样重要。后者包括：固氮酶中N_2还原为氨的6 e-还原，亚硫酸盐还原为硫化物的6 e-还原，亚硝酸盐还原为氨的6 e-还原，光合作用中2H_2O氧化为O_2的4 e-还原。该建议涉及a）参与多电子还原的金属酶和B）在氧化过程中具有活性的非卟啉、非Fe/S、铁中心的合成类似物的合成和研究。具体地说，研究了Fe/M/S（M=Mo，V）体系的合成、结构、光谱性质和反应活性。Fe/M/S簇有望作为固氮酶中Fe/M/S中心的合成类似物以及含有钒或铁代替钼的交替固氮酶。设计合成的新型Fe/S团簇作为固氮酶P-团簇的模型。合成了含有π受体配体的Fe/S簇的超分子组装体。并探讨了它们在催化剂活化和二氮催化还原中的可能作用。多核，混合配体，第一行元素的羧酸-儿茶酚复合物将被研究为催化各种底物的多电子氧化的酶中的活性位点的结构和反应模型。在这些化合物中的儿茶酚配体的功能，作为氧化等价物的存储站点，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.