IRON AND MOLYBDENUM COMPLEXES: ENZYME ACTIVE SITES

本研究计划涉及的合成，结构， 特定铁和钼的光谱和反应特性 配合物 新的Fe/S簇将被合成，预计 作为某些3Fe中Fe 3S 3或Fe 3S 4位点的合成类似物 蛋白质如乌头酸酶、D. gigas FdII、A、vinelandii FdI等。 从[Fe 6S 6L 6]2-，3-簇合物中可以得到新的Fe/S簇合物 最近在我们的实验室里发现并鉴定了。 后者将 完全用各种末端配体（L）和它们的 结构将通过X射线晶体学确定。 的目标之一 该建议是合成具有Fe：Mo：S比的Fe/Mo/S聚集体 接近6：1：8或9。 这个比例目前被认为是可能的比例。 固氮酶中Fe/Mo/S位点。 一个成功的模拟 固氮酶活性位点应该允许理解的催化 在生物系统中将二氮转化（还原）为氨。 这种反应也可能有助于我们理解小分子的 通常通过含催化金属的位点进行分子活化。 该提案的另一个具体目标是综合和完整 混合末端配体铁氧还蛋白活性位点类似物的表征 络合物如[Fe 4S 4LnLprime 4-n]2-，3-和[Fe 2S 2LnLprime 4-n]-2，3-， L = RS-、RO-和其它单负性单齿配体和L' -双齿配体 或具有0或N供体原子的三齿酶螯合配体。 这些集群是 有望作为固氮酶中P-簇的模型， 柠檬酸盐结合的Fe_4S_4簇。 稳定[Fe 4S 4]3+的尝试 通过替换1或2个生物型配体 (PhS-，Ph 0-）与已知的具有“有机金属”的合成类似物 配体C5 H5-及其衍生物。 这些新的混合末端配体簇是 预期经历双电子氧化还原反应，因此可能 对于小底物分子的还原是重要的。

This research proposal is concerned with the synthesis, structures, spectroscopic and reactivity properties of specific iron and molybdenum complexes. New Fe/S clusters will be synthesized, that are expected to serve as synthetic analogues of the Fe3S3 or Fe3S4 sites in certain 3Fe proteins such as aconitase, D. gigas FdII, A, vinelandii FdI, etc. These new Fe/S clusters will be obtained from the [Fe6S6L6]2-,3- clusters recently discovered and characterized in our laboratories. The latter will be completely characterized with various terminal ligands (L) and their structures will be determined by X-ray crystallography. One of the aims of this proposal is to synthesize Fe/Mo/S aggregates with a Fe:Mo:S ratio approaching 6:1:8 or 9. This ratio is presently accepted as possible ratio for the Fe/Mo/S site in nitrogenase. A successful analog for the nitrogenase active site should allow for an understanding of the catalytic conversion (reduction) of dinitrogen to ammonia in biological systems. This reaction also is potentially useful for our understanding of small molecule activation by catalytic metal containing sites in general. Another specific goal of this proposal is the synthesis and complete characterization of mixed-terminal ligand ferredoxin active site analog complexes such as [Fe4S4LnLprime4-n]2-,3- and [Fe2S2LnLprime4-n]-2,-3 with L = RS-, RO- and other uninegative monodentate ligands and L' - bidentate or tridentase chelate ligands with 0 or N donor atoms. These clusters are expected to serve as models for the P-clusters in nitrogenase and the citrate bound Fe4S4 cluster in aconitase. Attempts to stabilize [Fe4S4]3+ cores will be made by replacing 1 or 2 of the biological type ligands (PhS-, Ph0-) from known synthetic analogues with the "organometallic" ligand C5H5- and derivatives. These new mixed terminal ligand clusters are expected to undergo two-electron redox reactions and as such may be important for the reduction of small substrate molecules.