Osmium (Os) atoms are highly effective in promoting spin-orbit interactions due to their heavy molecular weight and could thus make efficient phosphorescent materials.

Researchers from Taiwan have now prepared a new series of octahedral Os(II) carbonyl complexes [Os(CO)₃X(dbm)] (X = CF₃CO₂, Cl, Br, I, SCN; dbmH = dibenzoylmethane) by using both solid-state pyrolysis and ligand exchange reactions (Y.-L. Chen, C. Sinha, I-C. Chen, K.-L. Liu, Y. Chi, J.-K. Yu, P.-T. Chou and T.-H. Lu, Chem. Commun., 2003, (24), 3046–3047). The skeletal arrangement consists of one β-diketonate chromophore (dmb)H to balance the +2 formal charge on the Os, one anionic ligand X and three orthogonal CO ligands located at the octahedral coordination site.

At room temperature, in CH₂Cl₂, the Os complexes exhibit prominent ³π–π* phosphorescence, with unusually long lifetimes (29–64 μs) and high quantum yields (0.08–0.13). These complexes have excellent photophysical and electrochemical properties, and may be employed in a variety of photochemical applications, such as organic light emitting diodes or photovoltaic devices.