Application of the energy gap law to the decay of charge-transfer excited states

It was suggested that in a series of osmium (II) polypyridyl compounds the properties of their metal-to-ligand charge-transfer (MLCT; Os/sup II/ ..-->.. ..pi..* (bpy) or (phen)) excited states including luminescence lifetimes, emission maxima, and redox potentials were systematically variable by making chemical changes. The authors have prepared a more extensive series of compounds and with the extended series are able to identify systematic variations in both nonradiative (k/sub nr/) and radiative rate constants (k/sup r/), and the systematic variations have important implications for transition-metal photochemistry. They give some relevant excited-state parameters for a series of mono- and bis-2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen) complexes of Os(II).