Slow triplet energy transfer to lower excited states in ruthenium(II) acylpyridine complexes

A few years ago they reported that locally excited acylpyridine (AP) triplets in Ru/sup II/(NH/sub 3/)/sub 5/AP complexes undergo relatively slow internal conversion (IL ..-->.. MLCT) to the lower lying metal-to-ligand charge-transfer states. At that time, they could merely place a maximum value of 10/sup 8/ s/sup -1/ on the rate constant k/sub ic/ for such internal conversion. They now can report the actual value more precisely. They also find that internal quenching of triplet acylpyridines in Ru/sup II/(bpy)/sub 2/(AP)/sub 2/ complexes by triplet energy transfer from acylpyridine to bipyridine is unexpectedly slow, unique behavior for two organic chromophores held so close together.