Relativistic Study on Emission Mechanism in Tris(2-phenylpyridine)iridium

The mechanisms of radiative processes from electronically excited states were investigated for tris(2-phenylpyridine)iridium [Ir(ppy) 3 ]. It was found that low-lying excited singlet and triplet states in the facial ( fac ) isomer are strongly mixed with each other by spin−orbit coupling (SOC) effects and, as a result, the radiative transitions could occur easily from low-lying spin-mixed states to the lowest spin-mixed state (ground state), where the low-lying spin-mixed states mainly have a triplet character. On the basis of the assumption that radiative processes obey Fermi's Golden rule, large transition probabilities are obtained between the sublevels of the adiabatic lowest triplet state (T 1 ) and the ground state (S 0 ), and phosphorescence is expected to be observed in this complex. This result is in good agreement with experimental reports.