Dual-Emissive Monoruthenium Complexes of N(CH)-Bridged Ligand: Synthesis, Characterization, and Substituent Effect.

Three monoruthenium complexes (PF)-(PF) bearing an N(CH)-bridged ligand have been synthesized and characterized. These complexes have a general formula of [Ru(bpy)()](PF), where is a 2,5-di(-methyl-'-(pyrid-2-yl)amino)pyrazine (dapz) derivative with various substituents, and bpy is 2,2'-bipyridine. The photophysical and electrochemical properties of these compounds have been examined. The solid-state structure of complex (PF) is studied by single-crystal X-ray analysis. These complexes show two well-separated emission bands centered at 451 and 646 nm (Δ = 195 nm) for (PF), 465 and 627 nm (Δ = 162 nm) for (PF), and 455 and 608 nm (Δ = 153 nm) for (PF) in dilute acetonitrile solution, respectively. The emission maxima of the higher-energy emission bands of these complexes are similar, while the lower-energy emission bands are dependent on the electronic nature of substituents. These complexes display two consecutive redox couples owing to the stepwise oxidation of the N(CH)-bridged ligand and ruthenium component. Moreover, these experimental observations are analyzed by computational investigation.