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首页> 外文学位 >Small molecule mimics of hydrogenase enzymes: Synthesis, protonation, and electrocatalysis.
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Small molecule mimics of hydrogenase enzymes: Synthesis, protonation, and electrocatalysis.

机译：氢化酶的小分子模拟物：合成，质子化和电催化。

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摘要

In nature, H2 is processed by enzymes called hydrogenases, which catalyze the reduction of protons to dihydrogen, as well as the reverse reaction. The active sites of the two most prevalent hydrogenases contain NiFe or FeFe cores, bound to thiolates, cyanide, and carbon monoxide ligands. These enzymes are also rich in Fe-S clusters to allow the necessary redox chemistry of hydrogen oxidation and production. Both enzymes operate at rates and overpotentials comparable with the best synthetic Pt catalysts. Due to growing concern over the climate effects of burning fossil fuels, there is a push to replace these fuels with carbon free alternatives, one option being H2. However, this would require catalysts for H2 production that are based on cheap, easily accessible metals. This problem inspired extensive research on the development of functional small molecule mimics of the hydrogenase enzymes. The work presented herein is motivated by the goal of understanding the mechanism of hydrogenase enzymes, in order to design better catalysts for hydrogen production. Chapter 1 presents an overview of current methods for the production of H2, including methods used in industry, as well as heterogeneous and homogeneous metal catalysts.;Chapter 2 describes the protonation of complexes of the type Fe2(xdt)(CO)4(dppv)2 (xdt= pdt, 1,2-propanedithiolate, or adtNH= azadithiolate; dppv= cis-1,2-bis(diphenylphosphino)ethylene, which form terminal hydrides that are stable at 0 °C for ~ 30 minutes and then isomerize to the corresponding bridging hydrides. Fe2(adtNH)(CO)4(dppv)2 undergoes protonation with weak acids, whereas, the pdt analogue requires strong acid; the difference being attributed to the presence of a pendant base in Fe2(adtNH)(CO)4(dppv)2, which is initially protonated and then relays the proton to the Fe center.;Chapter 3 describes the redox and catalytic properties of the terminal and bridging hydrides of Fe2(xdt)(CO)2(dppv)2. For both the adtNH and the pdt derivatives, the terminal hydride species are reduced at ~150 mV more mild potentials than the corresponding bridging hydrides. The voltammetry of [t-H Fe2(adtNH)(CO)2(dppv)2]+ is strongly affected by relatively weak acids and proton reduction catalysis proceeds at 5000 s-1 with an overpotential (the deviation from the thermodynamic reduction potential of the acid) of 0.7 V.;Chapter 4 describes the development of a new synthesis of complexes of the type (diphosphine)Ni(xdt)(CO)3, in which Fe(CO)4I2 condensed with Ni(xdt)(diphosphine), forming a NiIIFeII ?-iodide intermediate, which is then reduced to form the neutral NiFe complex. With this new synthetic method in hand, we synthesized of new derivatives, varying in the identity of the dithiolate, the diphosphine, and the ligands on the Fe center.;Chapter 5 describes the synthesis of new ferrous dicarbonyl dithiolato diphosphine complexes containing chelating diphosphine and dithiolate ligands. A new building block method for the synthesis of substituted diiron complexes of the type Fe2(xdt)(CO)4(diphosphine), by reaction of Fe(xdt)(CO)2(diphosphine) complexes with an Fe(0) tricarbonyl source, is described.;Chapter 6 describes the synthesis of bimetallic CpCo complexes of the type, (C5H5)Co(xdt)Co(C5H5) (xdt= pdt, 1,2-propanedithiolate; edt, 1,2 ethanedithiolate, and tdt= 3,4-toluenedithiolate), in an effort to synthesize more electron rich model complexes, by replacing the Fe(CO)3 unit with CpCo. These complexes undergo protonation to form bridging hydride species, which catalyze the reduction of protons, albeit at modest rates and fairly high overpotentials. (Abstract shortened by UMI.).
机译：实际上，H2是通过称为氢化酶的酶来处理的，该酶催化质子还原为二氢以及逆反应。两种最普遍的氢化酶的活性位点包含结合到硫醇盐，氰化物和一氧化碳配体上的NiFe或FeFe核心。这些酶还富含Fe-S团簇，以进行必要的氢氧化和氧化还原化学反应。两种酶均以与最佳合成Pt催化剂相当的速率和超电势运行。由于人们越来越关注燃烧化石燃料对气候的影响，因此人们正在寻求用无碳替代品替代这些燃料，其中一种选择是氢气。然而，这将需要基于廉价，易于获得的金属的H2生产催化剂。这个问题激发了对氢化酶功能小分子模拟物开发的广泛研究。本文提出的工作是出于理解氢化酶的机理的目的，以便设计出更好的制氢催化剂。第1章概述了目前生产H2的方法，包括工业上使用的方法以及非均相和均相金属催化剂。;第2章介绍了Fe2（xdt）（CO）4（dppv）型配合物的质子化）2（xdt = pdt，1,2-丙二硫代磺酸盐或adtNH =氮杂二硫代硫酸盐; dppv =顺式1,2-双（二苯基膦基）乙烯，形成末端氢化物，在0°C下稳定约30分钟，然后异构化Fe2（adtNH）（CO）4（dppv）2会用弱酸质子化，而pdt类似物则需要强酸；这种差异是由于Fe2（adtNH）（ CO）4（dppv）2，该质子首先被质子化，然后将质子传递到Fe中心。;第3章描述了Fe2（xdt）（CO）2（dppv）2的末端和桥接氢化物的氧化还原和催化性能对于adtNH和pdt衍生物，末端氢化物种类在〜150 mV时降低，具有更弱的电势比相应的桥接氢化物。 [tH Fe2（adtNH）（CO）2（dppv）2] +的伏安法受到相对弱的酸的强烈影响，质子还原催化以5000 s-1的超电势进行（偏离酸的热力学还原电势）的0.7 V .;第4章描述了新合成（diphosphine）Ni（xdt）（CO）3型配合物的进展，其中Fe（CO）4I2与Ni（xdt）（diphosphine）缩合形成NiIIFeIIα-碘化物中间体，然后将其还原以形成中性NiFe络合物。利用这种新的合成方法，我们合成了新的衍生物，其衍生物的二硫代酸酯，二膦和Fe中心的配体的身份各不相同。第5章介绍了新的含螯合二膦基亚铁的二羰基二硫代二硫杂亚铁二膦配合物的合成。二硫醇盐配体。通过Fe（xdt）（CO）2（diphosphine）配合物与Fe（0）三羰基源反应合成Fe2（xdt）（CO）4（diphosphine）型取代二铁配合物的新构造方法第6章描述了（C5H5）Co（xdt）Co（C5H5）类型的双金属CpCo配合物的合成（xdt = pdt，1,2-丙二硫代磺酸盐; edt，1,2，乙基二硫代硫酸盐和tdt = 3,4-toluenedithiothioate），以合成更多的电子富集的模型配合物，方法是用CpCo取代Fe（CO）3单元。这些配合物经历质子化反应，形成桥联氢化物，尽管能以适度的速率和相当高的过电势催化质子的还原。 （摘要由UMI缩短。）。

著录项

  • 作者

    Carroll, Maria Elizabeth.;

  • 作者单位

    University of Illinois at Urbana-Champaign.;

  • 授予单位 University of Illinois at Urbana-Champaign.;
  • 学科 Chemistry Inorganic.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 238 p.
  • 总页数 238
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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