Tuning of photocatalytic activity by creating a tridentate coordination sphere for palladium
作者:M. G. Pfeffer、L. Zedler、S. Kupfer、M. Paul、M. Schwalbe、K. Peuntinger、D. M. Guldi、J. Guthmuller、J. Popp、S. Gräfe、B. Dietzek、S. Rau
DOI:10.1039/c4dt01034e
日期:——
The synthesis and characterisation of an asymmetric potential bridging ligand bmptpphz (bmptpphz = 2,17-bis(4-methoxyphenyl)tetrapyrido[3,2-a:2′,3′-c:3′′,2′′-h:2′′′,3′′′-j] phenazine) is presented. This ligand contains a 1,10-phenanthroline (phen) and a 2,9-disubstituted phen sphere and possesses a strong absorbance in the visible. Facile coordination of the phen sphere to a Ru(tbbpy)2 core leads to Ru(bmptpphz) ([(tbbpy)2Ru(bmptpphz)](PF6)2; tbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine). UV-vis, emission, resonance Raman and theoretical investigations show that this complex possesses all properties associated with a Ru(tpphz) ([(tbbpy)2Ru(tpphz)](PF6)2; tpphz = tetrapyrido[3,2-a:2′,3′-c:3′′,2′′-h:2′′′,3′′′-j] phenazine) moiety and that the ligand based absorbances in the vis-part also populate an MLCT like state. The coordination of a Pd-core in the new 2,9-disubstituted phen sphere is possible, leading to a cyclometallation. The tridentate complexation leads to changes in the UV-vis and emission behaviour. Furthermore, the stability of the Pd-coordination is significantly enhanced if compared to the unsubstituted Ru(tpphz). Ru(bmptpphz)PdCl proved to be an active photocatalyst for H2 evolution, albeit with lower activity than the mother compound Ru(tpphz)PdCl2.
合成和表征了一种不对称的潜在桥接配体bmptpphz(bmptpphz = 2,17-二(4-甲氧基苯基)四吡啶[3,2-a:2′,3′-c:3′′,2′′-h:2′′′,3′′′-j]苯并吡咯),该配体包含一个1,10-菲咯啉(phen)和一个2,9-二取代的苯球,并在可见光区具有强吸收特性。苯球与Ru(tbbpy)₂核心的易于配位导致了Ru(bmptpphz)的形成([(tbbpy)₂Ru(bmptpphz)](PF₆)₂;tbbpy = 4,4′-二-tert-丁基-2,2′-联吡啶)。紫外-可见光、发射、共振拉曼和理论研究表明,该络合物具备与Ru(tpphz)([(tbbpy)₂Ru(tpphz)](PF₆)₂;tpphz = 四吡啶[3,2-a:2′,3′-c:3′′,2′′-h:2′′′,3′′′-j]苯并吡咯)部分相关的所有特性,并且基于配体的可见光区吸收也填充了类似MLCT的状态。在新的2,9-二取代苯球中,Pd核心的配位是可能的,从而导致环金属化。三齿配位导致紫外-可见光和发射行为的变化。此外,与未取代的Ru(tpphz)相比,Pd配位的稳定性显著增强。Ru(bmptpphz)PdCl证明是一种有效的光催化剂用于氢气演化,尽管其活性低于母体化合物Ru(tpphz)PdCl₂。