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

由于水和太阳光资源丰富且无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广泛关注。自从首次发现具有较强金属-金属相互作用的酰胺桥联Pt（II）_2二聚体的放氢活性以来，人们一直致力于开发由光敏Ru（bpy）_3^<2+>衍生物和Pt（II）催化剂组成的“光放氢（PHE）”分子器件。这类PHEMD有望作为一种高效的光催化剂，用于可见光诱导EDTA还原H_2_O为H_2。结果，我们发现了一种由[Ru（bpy）_2][5-amino-phen]^<2+>单元和PtCl_2（bpy）单元在EDTA存在下在可见光照射下放出H_2。为了更好地了解影响PHEMDs PHE活性的因素，还制备了几种其他相关化合物并进行了评价。关键因素：（i）填充Pt（II）dz^2轨道对应的HOMO失稳增强了PHE的活性，（ii）正方平面Pt（II）配位球轴向位置的空间位阻降低了PHE的活性，（iii）需要适当的芳香性来增强分子内电子转移过程，（iv）EDTA在进行H_2生成之前与PHEMD形成加合物，（iv）EDTA与PHEMD形成加合物。（v）H_2的生成是通过PHEMD的双分子过程进行的。除了这些结果，电化学研究，停流实验在Pt（II）配合物和甲基紫精产生的自由基阳离子之间的反应，和DFT MO调查已被检查。

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.