Influence of coordinate character on the photo-deactivate process for Pt(II) complex: A theoretical investigation

The influence of coordinate character on the photo-deactivate process for Pt(II) complex was detail explored through the density functional theory and time-dependent density functional theory. To illustrate the influence of coordinate character on the phosphorescent quantum yields, the SOC, transition dipole moments, oscillator strengths, the radiative decay rate constants, and photo-deactivation mechanisms are taken into account. Besides, the effect of triplet minimal points on the phosphorescent quantum yield is also discussed. The calculated results indicate that the large SOC matrix elements ⟨T1|HSOC|Sn⟩ can not facilitate the radiative decay rate constant, which is determined by transition dipole moments or oscillator strengths of Pt-1, Pt-2, and Pt-3. And, for Pt-3, due to the tetradentate coordination characteristics, the total reorganization energy is smaller than those of Pt-1 and Pt-2, which is beneficial for suppressing the temperature-independent decay processes. Moreover, the energy barriers between the 3ES and 3MC excited states, between the 3MC and MECP can be efficiently lifted in the tetradentate Pt(II) complex, suppressing the temperature-dependent decay process. Besides, the transformation between the different triplet minimal points is another predominant factor for the radiative and the non-radiative decay processes. Finally, the Pt-1 (T1B), Pt-2, and Pt-3 exhibit the narrow-band phosphorescent spectra can be attributed to strong rigidity to efficiently suppress other vibrational transitions and the maximum emission peaks corresponded to the 0-0 transition.