Several luminescent complexes of osmium (II) containing polypyridine ligands have been prepared. The syntheses, photophysical and fluorescence polarization properties of [Os(phen)2(aphen)]2+, [Os(tpy)(mcbpy)(py)]2+, [Os(ttpy)2]2+, [Os(tpy)(triphos)]2+ and [Os(tppz)2]2+ are reported. Where phen is 1,10-phenanthroline, aphen is 5-amino-1,10-phenanthroline, tpy is 2,2':6,2'-terpyridine, mcbpy is 4-methyl-2,2'- bipyridine-4'-carboxylic, py is pyridine, triphos is bis(2-diphenylphosphinoethyl)-phenyl phosphine, ttpy is 4- tolyl,2,2':6,2'-terpyridine, and tppz is 2,3,5,6- tetrakis(2-pyridyl)pyrazine. The complexes absorb light at above 550 nm, emit above 700 nm, and have emission lifetimes longer than 50 ns in water. The emission of all the complexes is polarized, so they can have applications as red light excitable dyes for biophysical studies of macromolecules and for polarization immunoassays. The complexes can also be used for lifetime-based oxygen sensing using low-cost phase fluorometry and a LED light source.