Tschierlei Stefanie, Presselt Martin, Kuhnt Christian, Yartsev Arkady, Pascher Torbjörn, Sundström Villy, Karnahl Michael, Schwalbe Matthias, Schäfer Bernhard, Rau Sven, Schmitt Michael, Dietzek Benjamin, Popp Jürgen
Institute for Physical Chemistry, Friedrich-Schiller University Jena, Helmholtzweg 4, 07743 Jena, Germany.
Chemistry. 2009 Aug 3;15(31):7678-88. doi: 10.1002/chem.200900457.
Photoinduced electron-transfer processes within a precatalyst for intramolecular hydrogen evolution (tbbpy)(2)Ru(tpphz)PdCl(2) (RuPd; tbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine, tpphz = tetrapyrido[3,2-a:2',3'c:3'',2'',-h:2''',3'''-j]phenazine) have been studied by resonance Raman and ultrafast time-resolved absorption spectroscopy. By comparing the photophysics of the (tbbpy)(2)Ru(tpphz) subunit Ru with that of the supramolecular catalyst RuPd, the individual electron-transfer steps are assigned to kinetic components, and their dependence on solvent is discussed. The resonance Raman data reveal that the initial excitation of the molecular ensemble is spread over the terminal tbbpy and the tpphz ligands. The subsequent excited-state relaxation of both Ru and RuPd on the picosecond timescale involves formation of the phenazine-centered intraligand charge-transfer state, which in RuPd precedes formation of the Pd-reduced state. The photoreaction in the heterodinuclear supramolecular complex is completed on a subnanosecond timescale. Taken together, the data indicate that mechanistic investigations must focus on potential rate-determining steps other than electron transfer between the photoactive center and the Pd unit. Furthermore, structural variations should be directed towards increasing the directionality of electron transfer and the stability of the charge-separated states.
通过共振拉曼光谱和超快时间分辨吸收光谱研究了用于分子内析氢的前催化剂(tbbpy)(2)Ru(tpphz)PdCl(2)（RuPd；tbbpy = 4,4'-二叔丁基-2,2'-联吡啶，tpphz = 四吡啶并[3,2-a:2',3'c:3'',2'',-h:2''',3'''-j]菲嗪）中的光诱导电子转移过程。通过比较(tbbpy)(2)Ru(tpphz)亚基Ru与超分子催化剂RuPd的光物理性质，将各个电子转移步骤归因于动力学成分，并讨论了它们对溶剂的依赖性。共振拉曼数据表明，分子集合的初始激发分布在末端tbbpy和tpphz配体上。Ru和RuPd在皮秒时间尺度上随后的激发态弛豫涉及以菲嗪为中心的配体内电荷转移态的形成，在RuPd中该状态先于Pd还原态的形成。异双核超分子配合物中的光反应在亚纳秒时间尺度上完成。综合来看，数据表明机理研究必须关注除光活性中心与Pd单元之间的电子转移之外的潜在速率决定步骤。此外，结构变化应旨在增加电子转移的方向性和电荷分离态的稳定性。
