Photo-hydrogen-evolving activity of chloro(terpyridine)platinum(II): a single-component molecular photocatalyst.
Photo-hydrogen-evolving activity of chloro(terpyridine)platinum(II): a single-component molecular photocatalyst.
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DOI：
10.1039/b905610f
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发表时间：
2009-07
影响因子：
4
通讯作者：
R. Okazaki;Shigeyuki Masaoka;K. Sakai
中科院分区：
文献类型：
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作者：
R. Okazaki;Shigeyuki Masaoka;K. Sakai
[PtCl(Terpy)]Clx2H(2)O(terpy=2，2‘：6’，2‘-联吡啶)(1Clx2H(2)O)是第一个在可见光照射下，以牺牲电子供体(EDTA)为供体的双功能体系，在水介质中促进光敏化和氢化活化的第一个例子。H(2)的生成速率与浓度1成平方关系，说明光诱导H(2)生成的总反应速率是由双分子路径决定的。结果表明，双分子机制通过形成所谓的(3)MMLCT激发态而在光敏化过程中起作用，从而形成双核光敏剂本身为氢化活化(MMLCT=金属-金属-配体电荷转移)提供了场所。ESI-TOF质谱仪证实了该络合物在光解过程中的稳定性。在没有汞和有汞存在的情况下都进行了光解，以排除胶体铂的形成。用乙酸盐、丙酸盐或磷酸盐作为缓冲剂代替典型实验中使用的MES(MES=2-吗啉乙磺酸)进行光解时，H(2)的析出速率显著降低。用电喷雾飞行时间质谱仪测定了MES、醋酸盐、丙酸盐和磷酸盐缓冲溶液中的主要化学物种分别为[PtCL(Terpy)](+)、[铂(乙酸基)(Terpy)](+)、[铂(丙酸)(Terpy)](+)和[铂(H(2)PO4)(Terpy)](+)。结果表明，初始氯物种(即[PtCl(Terpy)](+))在光化学H(2)的形成中起着关键作用。H(2)的形成与EDTA浓度有关的饱和动力学表明，1的二聚体(即(1)(2)(2+))与EDTA的双阴离子形式形成离子对加合物，以促进EDTA在光化学过程中的电子注入。
[PtCl(terpy)]Cl x 2 H(2)O (terpy = 2,2':6',2''-terpyridine) (1Cl x 2 H(2)O) is the first example serving as a bifunctional system promoting both photosensitization and hydrogenic activation as an H(2)-evolving catalyst in aqueous media in the presence of a sacrificial electron donor (EDTA) under visible-light illumination. The rate of H(2) formation has turned out to be quadratic to the concentration of 1, suggesting that a bimolecular path determines the overall reaction rate for the photoinduced H(2) formation. It is suggested that the bimolecular mechanism operates at the photosensitization process through the formation of the so-called (3)MMLCT excited state and thus formed dinuclear photosensitizer itself provides a site for the hydrogenic activation (MMLCT = metal-metal-to-ligand charge transfer). The stability of the complex during the photolysis was successfully confirmed by ESI-TOF mass spectrometry. The photolysis was carried out in both the absence and the presence of mercury to rule out the formation of colloidal platinum. The rate of H(2) evolution considerably decreases when the photolysis was carried out by using acetate, propionate, or phosphate as a buffer reagent instead of MES (MES = 2-morpholinoethanesulfonic acid), which was used in typical experiments. The major chemical species in MES, acetate, propionate, and phosphate buffer solutions were respectively ascertained to be [PtCl(terpy)](+), [Pt(acetato)(terpy)](+), [Pt(propionato)(terpy)](+) and [Pt(H(2)PO(4))(terpy)](+) by ESI-TOF mass spectrometry. It is concluded that the original chloro species (i.e., [PtCl(terpy)](+)) plays a crucial role in the photochemical H(2) formation. The saturation kinetics for the H(2) formation with regard to the EDTA concentration was observed, revealing that the dimer of 1 (i.e., (1)(2)(2+)) and the dianionic form of EDTA form an ion-pair adduct to facilitate the electron injection from EDTA during the photochemical processes.