NATURE OF THE EMITTING (3)MLCT MANIFOLD OF RHENIUM(I) (DIIMINE) (CO)(3)CL COMPLEXES

Spectroscopic investigations of four Re(NN)(CO)3Cl complexes (NN=2,2'-bipyridine, 4,4'-dimethyl-2,2-bipyridine, 1,10-phenanthroline, or 2,9-dimethyl-1,10-phenanthroline) in the 77-4 K range reveal a single 3MLCT emitting configuration. Temperature dependences of the phosphorescence lifetimes have been analyzed in terms of a multiple state model that yields rate constants and level splittings. A model based on C2v symmetry that depends on second-order spin-orbit coupling between dpi* configurations is proposed to rationalize the results. Implications for the well-studied Ru(NN)32+ and Os(II)(NN)32+ manifolds are discussed.