Our results can assist engineering of OCCs in other neutral or charged molecules. In particular, a shortening of the radiative lifetime in the most promising 1 2 Σ → 1 2 ∆ scheme appears possible. The radiative lifetime of an excited state becomes shorter with an increase in either the excitation energy or the transition dipole moment. A use of polyatomic ligands of an electron withdrawing strength exceeding that of atoms appears as the most practical way of raising transition energy. The excitation energy can be further increased with the growing number of the metal-ligand bonds. Similarly, a formally dipole forbidden transition can become sufficiently bright in molecules with heavy nuclei due to an increased SOCs. We expect that the heavy metal analogs of the systems studies in this work (Lu, Hf, Ta cations) are likely to feature fast OCCs on a transition between its low-lying doublet states and that the design principle outlined before should help in its fine-tuning.