NONRADIATIVE DECAY IN RHENIUM(I) MONOMETALLIC COMPLEXES OF 2,3-DI-2-PYRIDYLPYRAZINE

The nonradiative (k(nr)) decay rates of the low-lying, emissive metal-to-ligand charge-transfer (MLCT) excited states of a series of complexes of the type [Re(dpp)(CO)3L]+ (dpp = 2,3-di-2-pyridylpyrazine; L = Cl-, N-methylimidazole, pyridine, 4-phenylpyridine, 4-methylpyridine, trimethylphosphine, acetonitrile) have been investigated. The results show that the "energy gap law" for radiationless decay in the weak coupling limit is obeyed by this series of complexes. The complexes yield a ln k(nr) vs E(em) plot with a slope and intercept within experimental error for two separate studies on the series where the acceptor ligand is 2,2'-bipyridine. This is taken as evidence that dpp and bpy differ only in the relative energies of the acceptor orbitals and are vibrationally similar.