Mechanistic Studies of the Photoactivation of Metal- Hydride, Halide and Oxo Bonds

有了这个奖项，化学系的化学催化项目正在资助哈佛大学的丹尼尔诺切拉教授研究可以从光和简单化合物中产生氢气的催化过程。 燃料是与氧化剂（通常是氧气）反应释放能量的化合物。在分子水平上，当燃料燃烧时，高能化合物中的键重新排列，在较低能量的化合物中形成新的键，这种键重新排列释放的能量用于为我们的世界提供动力。我们社会中的大多数燃料来自煤、石油和天然气;即化石燃料，其键与氧的键重新排列，产生二氧化碳和水，进入大气层。 避免二氧化碳形成的一种方法是切断燃料和碳之间的联系，并使用氢作为燃料。有两种来源的氢可以使用太阳辐射产生：水或氢卤酸（例如，氢原子键合到氯原子）;然而，氢不能通过直接照射水或氢卤酸来产生。必须使用催化剂来捕获光，然后在键重排反应中充当中间体。Nocera教授正在开发新的催化剂，可以吸收光，然后将氢卤酸转化为氢和元素卤素。 从这项研究中产生的新化合物，反应和技术可能会影响相关的科学领域，并可能导致新的能源生产技术。 Nocera教授继续参与提高公众对全球能源问题以及科学，特别是化学在应对能源挑战方面可以发挥的作用的认识。这一领域的研究成果正在通过各种论坛，包括新闻媒体、广播节目、电影和其他广播场所向公众传达。Nocera小组正在开发光化学HX分解的新催化剂，同时正在研究这种反应的机理。 以燃料的形式储存可再生能源需要将具有低能量含量的键重排为具有高能量含量的键，并且重要的能量后果的键是H-H、X-X和O=O。正在合成基于Rh、Ni、Fe和Mn的新金属化合物，这些化合物可以提供对这些能量转换过程的深入了解。正在使用先进的光谱技术研究促进必要的键活化的关键中间体，包括应用时间分辨X射线晶体学和基于纳米颗粒的时间分辨共振拉曼光谱学来鉴定关键的M-H和M-X中间体，以及磁共振技术（中场ENDOR，ELDOR检测的NMR和单晶极化中子衍射）用于鉴定M-O中间体。随着关键中间体的立体电子性质的知识，光循环被构建为驱动能量向上的反应，这是可再生能源转换的基础。

With this award, the Chemical Catalysis Program of the Chemistry Division is funding Professor Daniel Nocera of Harvard University to study catalytic processes that can generate hydrogen from light and simple compounds. Fuels are compounds that react with an oxidant, usually oxygen, to release energy. At the molecular level, when a fuel is burned, the bonds in high energy compounds rearrange to form new bonds in lower energy compounds, and the energy released in this bond rearrangement is used to power our world. Most fuels in our society are derived from coal, oil and natural gas; namely fossil fuels, the bonds of which are rearranged with the bonds of oxygen to generate carbon dioxide and water, which enter the atmosphere. One way to avoid the formation of carbon dioxide is to cut the connection between fuels and carbon and to use hydrogen as a fuel. There are two sources of hydrogen that can be generated using solar irradiation: water or hydrohalic acid (for example, a hydrogen atom bonded to a chlorine atom); however, hydrogen cannot be generated by shining light directly on water or hydrohalic acid. A catalyst must be used that will capture the light and then act as an intermediary in the bond rearrangement reaction. Professor Nocera is developing new catalysts that can absorb light and then convert hydrohalic acids into hydrogen and elemental halogen. The new compounds, reactions and techniques resulting from this research are likely to impact realted areas of science and could result in new energy generation technologies. Professor Nocera continues to be involved in raising public awareness of the global energy problem and the role that science, and especially chemistry, can play in addressing the energy challenge. Research discoveries in this area are being conveyed to the public through a variety of forums including news media, radio programs, movies and other broadcast venues. The Nocera group is developing new catalysts for photochemical HX splitting and, in parallel, is studying the mechanisms of such reactions. The storage of renewable energy in the form of fuels requires the rearrangement of bonds with low energy content to ones of high energy content, and bonds of important energy consequence are H-H, X-X and O=O. New metal compounds based on Rh, Ni, Fe and Mn are being synthesized that can provide insight into these energy conversion processes. Critical intermediates that promote the requisite bond activation are being studied using advanced spectroscopic techniques, including the application of time-resolved X-ray crystallography and nanoparticle-based time-resolved resonance Raman spectroscopy for the identification of the critical M-H and M-X intermediates, and magnetic resonance techniques (intermediate-field ENDOR, ELDOR-detected NMR and single-crystal polarized neutron diffraction) for the identification of M-O intermediates. With knowledge of the stereoelectronic properties of the critical intermediates, photocycles are being constructed to drive energetically uphill reactions, which are at the basis for renewable energy conversion.