The kinetics of the lowest excited [sup 3][pi]-[pi]* states of the complex cations [Rh(thpy)[sub 2](bpy)][sup +] and [Rh(thpy)(phpy)(bpy)][sup +] (thpy = 2,2[prime]-thienylpyridine, phpy = 2-phenylpyridine, bpy = bipyridine), co-doped in a single crystal of [Rh(phpy)[sub 2](bpy)]PF[sub 6], has been studied by means of optically detected microwave recovery and adiabatic rapid passage experiments. The population decay of the ligand-localized triplet-state sublevels in the complex cations is found to be 3 orders of magnitude faster than in the free ligand molecules. The decay of the [sup 3][pi]-[pi]* states of the complex cations is largely radiative in nature. The enhanced radiative decay is discussed to arise from selective spin-orbit coupling-induced mixing with [sup 1]d-[pi]* charge-transfer configurations. In these [sup 1]d-[pi]* configurations, metal ion d-orbitals forming a molecular orbital with ligand orbitals via [sigma]-bonding are of particular relevance for explaining the differences among the emissive properties of the triplet-state sublevels as determined experimentally. 39 refs., 4 figs., 4 tabs.