Novel Ru(II)/Os(II)‐Exchange Homo‐ and Heterometallic Polypyridyl Complexes with Effective Energy Transfer

Abstract Two novel homometallic Ru−Ru and heterometallic Ru−Os dimers and trimers, [M II (bpy) 2 (4‐tpy‐4′‐methyl‐2,2′‐bipyridine)M II (tpy)] 4+ and [M II (bpy) 2 ](4‐tpy‐4′‐tpy‐2,2′‐bipyridine)(M II (tpy)) 2 ] 6+ , have been first prepared and characterized. Electrochemical properties of the metal‐based reversible oxidation and ligand‐based reduction are measured. Spectroscopic analysis of these complexes exhibits for every Ru‐ or Os‐based subunit an individual intense absorption spectrum extended over the entire UV and visible region. The heteronuclear complexes [Ru II (bpy) 2 (4‐tpy‐4′‐methyl‐2,2′‐bipyridine)Os II (tpy)] 4+ , [Ru II (bpy) 2 ](4‐tpy‐4′‐tpy‐2,2′‐bipyridine)(Os II (tpy)) 2 ] 6+ , and [Os II (bpy) 2 ](4‐tpy‐4′‐tpy‐2,2′‐bipyridine)(Ru II (tpy)) 2 ] 6+ display a weak emission spectrum in the near‐infrared region (NIR). The luminescence of the polynuclear assemblies is quantitatively quenched, by intramolecular energy transfer to the lower‐lying metal‐to‐ligand charge transfer ( 3 MLCT) and metal‐centered ( 3 MC) state of the Os(II)‐based center or Ru(II)‐terpyridine moiety at room temperature.