Department of Chemistry, Faculty of Science, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
Chem Asian J. 2010 Aug 2;5(8):1860-9. doi: 10.1002/asia.201000083.
The mechanism of photoinduced hydrogen evolution from water driven by the first photo-hydrogen-evolving molecular catalyst (1), given by a coupling of Ru(bpy)(2)(5-amino-phen) and [PtCl(2)(4,4'-dicarboxy-bpy)] (bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline), was investigated in detail. The H(2) evolution rate was found to obey Michaelis-Menten enzymatic kinetics with regard to the concentration of EDTA (ethylenediamine tetra-acetic acid disodium salt, sacrificial electron donor), which indicates that an ion-pair formation between the dicationic 1 and the dianionic form of EDTA (pH 5) is a key step leading to H(2) formation. A 2:1 coupling product of 1 and ethylenediamine (i.e., a {Ru(II) (2)Pt(II) (2)} complex 2) was found to show significantly higher photo-hydrogen-evolving (PHE) activity than 1, which revealed the validity of the bimolecular activation proposed in our previous study. The PHE activity of 2 was also observed to be linear to the concentration of 2, which indicates that H(2) formation through the intermolecular path competes with the intramolecular path. Molecular orbital diagrams, conformational features, and PtH(water or acetic acid) hydrogen bonds were characterized by DFT calculations.
详细研究了由 Ru(bpy)(2)(5-氨基-菲) 和 [PtCl(2)(4,4'-二羧酸联吡啶)]（bpy = 2,2'-联吡啶，phen = 1,10-菲咯啉）偶联形成的首例光致氢析出分子催化剂（1）驱动的水的光致氢析出的反应机制。发现 H2 析出速率与 EDTA（乙二胺四乙酸二钠盐，牺牲电子供体）的浓度符合米氏酶动力学，这表明二阳离子 1 和 EDTA 的二阴离子形式（pH 5）之间的离子对形成是导致 H2 形成的关键步骤。发现 1 和乙二胺的 2:1 偶联产物（即 {Ru(II) (2)Pt(II) (2)} 配合物 2）比 1 具有显著更高的光致氢析出（PHE）活性，这证实了我们之前研究中提出的双分子活化的有效性。还观察到 2 的 PHE 活性与 2 的浓度呈线性关系，这表明通过分子间途径形成 H2 与分子内途径竞争。通过 DFT 计算，对分子轨道图、构象特征和 PtH（水或乙酸）氢键进行了表征。
