Relaxation and luminescence processes in photo-excited phosphorescent Pt^<2+> -compound N^N^C-Pt(Cl)

Numerical analysis is made for the photoluminescence (PL) lifetime and intensity of cyclometalated Pt-compound N^N^C-Pt(Cl), by taking into account non-radiative relaxations among three zero-field splitting substates of triplet T_1 state and energy dissipation from the substates to unexcited neighboring N^N^C-Pt(Cl) and by solving the rate equations for the three substates. From the fitting between the calculated and observed temperature dependences of PL lifetime and intensity, large zero-field splitting of 90cm and short radiative lifetime of 1.9 μs were obtained. It is suggested that the energy dissipation is responsible for the decrease of PL intensity with increasing temperature