2,3-Di(2-pyridyl)-5-phenylpyrazine: A NN-CNN-Type Bridging Ligand for Dinuclear Transition-Metal Complexes

Graphical NN-CNN breaking news : 2,3-Di(2-pyridyl)-5-phenylpyrazine, which is able to bind two metals through a NN-CNN-type coordination mode, has been designed and synthesized. A RuPt heterobimetallic complex with this bridging ligand shows near-infrared emission at 750 nm, with a quantum yield of 0.41 % and an excited-state lifetime of 170 ns. en This link goes to a English section zh This link goes to a English section A new bridging ligand, 2,3-di(2-pyridyl)-5-phenylpyrazine (dpppzH), has been synthesized. This ligand was designed so that it could bind two metals through a NN-CNN-type coordination mode. The reaction of dpppzH with cis -[(bpy) 2 RuCl 2 ] (bpy=2,2′-bipyridine) affords monoruthenium complex [(bpy) 2 Ru(dpppzH)] 2+ ( 12+ ) in 64 % yield, in which dpppzH behaves as a NN bidentate ligand. The asymmetric biruthenium complex [(bpy) 2 Ru(dpppz)Ru(Mebip)] 3+ ( 23+ ) was prepared from complex 12+ and [(Mebip)RuCl 3 ] (Mebip=bis( N -methylbenzimidazolyl)pyridine), in which one hydrogen atom on the phenyl ring of dpppzH is lost and the bridging ligand binds to the second ruthenium atom in a CNN tridentate fashion. In addition, the RuPt heterobimetallic complex [(bpy) 2 Ru(dpppz)Pt(CCPh)] 2+ ( 42+ ) has been prepared from complex 12+ , in which the bridging ligand binds to the platinum atom through a CNN binding mode. The electronic properties of these complexes have been probed by using electrochemical and spectroscopic techniques and studied by theoretical calculations. Complex 12+ is emissive at room temperature, with an emission λ max =695 nm. No emission was detected for complex 23+ at room temperature in MeCN, whereas complex 42+ displayed an emission at about 750 nm. The emission properties of these complexes are compared to those of previously reported Ru and RuPt bimetallic complexes with a related ligand, 2,3-di(2-pyridyl)-5,6-diphenylpyrazine. en This link goes to a English section zh This link goes to a English section 1