Synthesis and Characterization of Tris(bidentate) Ruthenium Complexes of Di(pyrid‐2‐yl)(methyl)amine

Three tris(bidentate) monoruthenium complexes [Ru(dpma)(bpy)2](PF6)2 [1(PF6)2; dpma = di(pyrid‐2‐yl)(methyl)amine, bpy = 2,2′‐bipyridine], [Ru(dpma)2(bpy)](PF6)2 [2(PF6)2], and [Ru(dpma)3](PF6)2 [3(PF6)2] with the electron‐rich ligand dpma were synthesized and characterized. The single‐crystal X‐ray structures of 1(PF6)2 to 3(PF6)2 are presented. The electrochemical and spectroscopic properties of these complexes were examined and compared with those of the reference complex [Ru(bpy)3](PF6)2. Complexes 1(PF6)2 to 3(PF6)2 show a decreased RuIII/II redox potential by 140–310 mV with respect to [Ru(bpy)3](PF6)2. The strong emission property of [Ru(bpy)3](PF6)2 is maintained in 1(PF6)2 and 2(PF6)2. However, complex 3(PF6)2 is only weakly emissive at room temperature. In addition, density functional theory (DFT) and time‐dependent DFT calculations were performed to complement these experimental results.