Ground- and excited-state electronic structure of an emissive pyrazine-bridged ruthenium(II) dinuclear complex

The synthesis, characterization, and electrochemical, photophysical, and photochemical properties of the binuclear compounds [(Ru(H8-bpy) 2)2((Metr)2Pz)](PF6)2 (1) and [(Ru(D8-bpy)2)2((Metr)2Pz)] (PF6)2 (2), where bpy is 2,2′-bipyridine and H 2(Metr)2Pz is the planar ligand 2,5-bis(5′-methyl- 4′H-[1,2,4]triaz-3′-yl)-pyrazine, are reported. Electrochemical and spectro-electrochemical investigations indicate that the ground-state interaction between each metal center is predominantly electrostatic and in the mixed-valence form only a low level of ground-state delocalization is present. Resonance Raman, transient, and time-resolved spectroscopies enable a detailed assignment to be made of the excited-state photophysical properties of the complexes. Deuteriation is employed to both facilitate spectroscopic characterization and investigate the nature of the lowest excited states.