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Energy-Controlled Spaces at the Single-Molecule Photo-Hydrogen-Evolving Devices

单分子光放氢装置的能量控制空间

基本信息

批准号：
16074216
负责人：
SAKAI Ken
金额：
$ 4.93万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

Great attention has been paid to the studies on the photocatalytic systems promoting the solar-light-induced splitting of water into H_2 and 1/2O_2, because water and sunlight are abundant and such systems are free of the CO_2 emission. Since the original discovery in the H_2-evolving activities of amidate-bridged Pt(II)_2 dimers having a relatively strong metal-metal interaction, considerable efforts have been made to develop the 'photo-hydrogen-evolving (PHE)' molecular devices (MDs) that are made up of photosensitizing Ru(bpy)_3^<2+> derivatives and H_2-evolving Pt(II) catalysts. Such PHEMDs are expected to serve as an efficient 'photocatalyst'towards the visible-light-induced reduction of H_2_O by EDTA into H_2. As a result, we discovered that one particular molecular device consisting of a [Ru(bpy)_2(5-amino-phen)]^<2+> unit and a PtCl_2(bpy) unit evolves H_2 in the presence of EDTA under the visible light illumination.In this project, several other related compounds have also been prepared and evaluated to better understand the factors affecting the PHE activities of such PHEMDs These studies suggested the following key factors: (i) destabilization of the HOMO corresponding to the filled Pt(II) dz^2 orbital enhances the PHE activity; (ii) steric hindrances around the axial site of the square-planar Pt(II) coordination sphere lower the PHE activity; (iii) an appropriate aromaticity is needed to enhance the intramolecular electron transfer processes; (iv) EDTA forms an adduct with a PHEMD before undertaking the H_2 generation; (v) the H_2 formation undergoes via a bimolecular process of the PHEMD. In addition to these results, the electrochemical studies, stopped flow experiments looking at the reactions between the Pt(II) complexes and a radical cation generated from methylviologen, and DFT MO investigations have been examined.

由于水和阳光充足，且无CO_2排放，促进太阳光诱导水分解为H_2和1/2O_2的光催化体系的研究受到了极大的关注。自从首次发现具有较强金属-金属相互作用的酰胺桥联铂(II)2二聚体的析氢活性以来，人们一直致力于发展由光敏化Ru(Bpy)3^和lt；2+&gt；衍生物和析氢铂(II)催化剂组成的“光放氢(PHE)”分子器件。这类PHEMDs有望成为可见光诱导EDTA将H_2O还原为H_2的有效“光催化剂”。在这个项目中，为了更好地了解影响这类PHEMD活性的因素，我们还制备了其他几种相关化合物，并对其进行了评价。这些研究提出了以下关键因素：(I)填充的铂(Ii)Dz^2轨道对应的HOMO的失稳提高了Phe的活性；(Ii)正方形平面铂的轴位周围的空间位阻使Phe活性降低；(Iii)需要适当的芳香性来增强分子内的电子转移过程；(4)EDTA在生成H_2之前与PHEMD形成加合物；(V)H_2的形成是通过PHEMD的双分子过程进行的。除这些结果外，还对铂(II)络合物与甲基紫精生成的自由基阳离子之间的反应进行了电化学研究、停流实验和密度泛函理论研究。