Synthesis and Characterization of Trisbidentate Ruthenium Complexes of Di(pyrid-2-yl)-methylamine

Three tris-bidentate monoruthenium complexes [Ru(dpma)(bpy)2](PF6)2 (1(PF6)2, dpma = di(pyrid-2-yl)-methylamine; 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 - 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 - 3(PF6)2 show a decreased Ru(III/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