Synthesis and characterization of osmium(II) complexes incorporating polypyridyl bridging ligands
A series of osmium(II) compounds have been prepared which contain the polypyridyl bridging ligands 2,3-bis(2′-pyridyl)pyrazine (dpp), 2,3-bis(2′-pyridyl)quinoxaline (dpq) and 2,3-bis(2′-pyridyl)benzoquinoxaline (dpb). The compounds [Os(bpy)2(dpp)](PF6)2, [Os(bpy)2(dpq)](PF6)2 and [Os(bpy)2(dpb)](PF6)2 (bpy=2,2′-bipyridine) have been synthesized and their electrochemical and spectroscopic properties have been studied and are reported herein. The complexes show absorbances throughout the visible region of the spectrum. The potential of the first electrochemical reduction as well as the energy of the lowest energy metal to ligand charge transfer excited state (MLCT) are found to be dependent upon the nature of the bridging polypyridyl ligand. This combined with the fact that the bridging ligands are more easily reduced than bipyridine support the assignment of the lowest unoccupied molecular orbital (LUMO) as arising from a bridging ligand based π* orbital.
Richter, Mark M., and Karen J. Brewer. "Synthesis and characterization of osmium (II) complexes incorporating polypyridyl bridging ligands." Inorganica chimica acta 180, no. 1 (1991): 125-131.
Inorganica Chimica Acta