Theoretical Insights into the Photo-Deactivation of Emitting Triplet Excited State of (C^N)Pt(O^O) Complexes: Radiative and Nonradiative Decay Processes

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• 作者：Yanyan Xu ; Yafei Luo ; Ming Li ; Rongxing He ; Wei Shen
• 刊名：Journal of Physical Chemistry A
• 出版年：2016
• 出版时间：September 1, 2016
• 年：2016
• 卷：120
• 期：34
• 页码：6813-6821
• 全文大小：455K
• 年卷期：0
• ISSN：1520-5215

文摘

In this study, density functional theory (DFT) and time-dependent DFT were employed to elucidate the photo-deactivation mechanisms of (C^N)Pt(O^O) complexes 1–4 (where C^N = 2-phenylpyridine derivatives, O^O = dipivolylmethanoate). To make thorough understanding of the radiative decay, the singlet–triplet splitting energies ΔE(S_n–T₁) (n = 1, 2, 3, 4, ...), transition dipole moment μ(S_n) for S₀–S_n transitions and the spin–orbit coupling (SOC) matrix elements ⟨T₁|H_SOC|S_n⟩ were all calculated. Moreover, the spin–orbit coupling between T₁ and S₀ ⟨T₁|H_SOC|S₀⟩ and Huang–Rhys factors were calculated to estimate the temperature-independent nonradiative decay processes. Meanwhile, the thermal deactivation via metal-centered ³MC was described to analyze the temperature-dependent nonradiative decay processes. As a result, the effective SOC interaction between the lowest triplet and singlet excited states successfully rationalize why complexes 1 and 3 have higher radiative decay rate constant than that of complex 2, while the larger ⟨T₁|H_SOC|S₀⟩ and lower energy barrier for thermal deactivation in 3 reasonably explains why 3 has larger nonradiative rate than that of 1 and 2. Consequently, it can be concluded that it is the ⟨T₁|H_SOC|S₀⟩ and thermal population of ³MC that account for the nonemissive behavior of (C^N)Pt(O^O) complexes, and controlling π-conjugation is an efficient method for tuning phosphorescence properties of transition-metal complexes.