Tuning of Photocatalytic Hydrogen Production and Photoinduced Intramolecular Electron Transfer Rates by Regioselective Bridging Ligand Substitution
Tuning of Photocatalytic Hydrogen Production and Photoinduced Intramolecular Electron Transfer Rates by Regioselective Bridging Ligand Substitution
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DOI：
10.1002/cphc.201100245
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发表时间：
2011-08-01
期刊：
影响因子：
2.9
通讯作者：
Popp, Juergen
中科院分区：
文献类型：
--
作者：
Karnahl, Michael;Kuhnt, Christian;Popp, Juergen
基于超分子光催化剂的人工光合作用提供了独特的可能性，可以非常详细地研究光子催化转化为化学燃料的分子过程，并通过改变分子框架来调节光催化剂的性质。在本文中，我们集中于研究通过众所周知的光催化剂[（tbbpy）（2）Ru（tpphz）PdCl 2]（PF 6）（2）[4，4 '-二叔丁基-2，2'-联吡啶（tbbpy），四吡啶并[3，2-a：2 '，3'-c：3“”，2“”-h：2“”，3“”-j]吩嗪（tpphz）]的衍生物的质子的光催化还原的两种可能性。我们报道了一种将关键的桥连配体tpphz用溴取代的改性光催化剂，并研究了结构变化对配合物催化性能及其超快分子内电荷转移行为的影响。结果发现，结构修饰稳定的邻菲咯啉为中心的金属-配体上的tpphz部分的电荷转移状态，从而降低了整个电子中继桥接配体的电子转移梯度，并在同一时间加速纳秒基态恢复。相同的结构修饰导致络合物的催化活性的总体降低。因此，这些结果突出了超分子催化剂的分子框架中的小结构变化在理解光诱导电荷转移过程和优化其催化性能方面的潜力。
Artificial photosynthesis based on supramolecular photocatalysts offers the unique possibility to study the molecular processes underlying catalytic conversion of photons into chemical fuels in great detail and to tune the properties of the photocatalyst by alterations of the molecular framework. Herein we focus on both possibilities in studying the photocatalytic reduction of protons by derivatives of the well-known photocatalyst [(tbbpy)(2)Ru(tpphz)PdCl2](PF6)(2) [4,4'-di-tert-butyl-2,2'-bipyridine (tbbpy), tetrapyrido[3,2-a:2',3'-c:3 '',2 ''-h:2'", 3'"-j]phenazine (tpphz)]. We report on a modified photocatalyst where the crucial bridging ligand tpphz is substituted by bromine and investigate the effect of the structural variation on the catalytic properties of the complex and its ultrafast intramolecular charge transfer behavior. It is found that structural modification stabilizes the phenanthroline-centered metal-to-ligand charge-transfer state on the tpphz moiety, thereby reducing the electron transfer gradient across the entire electron-relaying bridging ligand and at the same time accelerating nanosecond ground-state recovery. The same structural modifications cause an overall reduction of the catalytic activity of the complex. Thus, the results highlight the potential of small structural variations in the molecular framework of supramolecular catalysts in understanding the photoinduced charge-transfer processes and optimizing their catalytic performance.