Crystallography and luminescence of divalent osmium complexes green osmium emitters and possible evidence for d-orbital backbonding

The preparation, photophysics, and solid-state structures of three osmium cored complexes are reported. The osmium complexes take the general form of [OsCl(N-N)(L-L)(CO)]⁺ hexafluorophosphate where N stands for a derivative of 1,10-phenanthroline and L stands for a phosphine type ligand. The emission of the complexes is shown to be blue shifted to the osmium emission of Os(bpy)₃²⁺. The emissions of the various complexes range from yellow (560 nm) to yellow-green (550 nm) to green (520 nm). The quantum yields vary between 60% and 75%. The complexes show lifetimes that are much longer than expected with ranges of 6.5-38 μs. Crystallographic results show that the carbonyl is trans to a phenanthroline nitrogen and the chloro ligand is trans to phosphorus. A discussion will be presented as to the nature of the bonding in these complexes based upon the data from the crystallography.