Heteroleptic ruthenium(II) complexes based on 6,6′-disubstituted 4,4′-bipyrimidines: New room temperature red-emitting species

A new series of heteroleptic ruthenium(II) complexes based on 6,6′-disubstituted 4,4′-bipyrimidines (bpm) and two 2,2′-bipyridine (bpy) ligands have been prepared and their spectroscopic and electrochemical properties have been investigated. The complexes exhibit Ru-to-bpm metal-to-ligand charge transfer (MLCT) absorptions centered at about 540 nm and Ru-to-bpy MLCT absorptions centered at about 435 nm. The new complexes are emissive at room temperature in fluid solution and they are among the longest wavelength emitters (λmax > 780 nm) based on tris-bidentate mononuclear Ru(II) complexes known.