位移谐振子模型对三(2-苯基吡啶)合铱磷光光谱影响的理论研究（英文）

Theoretical Study of the Phosphorescence Spectrum of Tris(2-phenylpyridine)iridium Using the Displaced Harmonic Oscillator Model

采用谐振子模型理论探讨了振动模式对Ir(ppy)3配合物的磷光光谱的影响.多原子分子发射光谱的一般形式可以从两个绝热电子态之间的热振动关联函数推导出,相应地势能面之间的位移和Duschinsky转动的影响也被包含在多维谐振子模型的表达式中,所得关系式模拟出了Ir(ppy)3较为精细的磷光发射光谱.计算结果表明T1态到S0态之间的0→1振动跃迁对发射光谱贡献较大,尤其振动频率小于1600 cm–1的振动模贡献更多,配体中苯和吡啶环上C=C和C=N的呼吸振动,是Ir(ppy)3出现肩峰的主要原因.玻耳兹曼分布使得主峰和肩峰的强度下降,并且两峰相互接近.该谐振子模型与密度泛函理论(DFT)结合,可以较好地定量描述多原子分子光物理过程的发射光谱以及详细了解光谱谱图的细节.

We present a comprehensive investigation of the phosphorescence spectrum of Ir（ppy）3（ppy =2-phenylpyridine）, which is greatly influenced by vibration of the complex. General formalism of the emission spectrum is derived using a thermal vibration correlation function formalism for the transition between two adiabatic electronic states in polyatomic molecules. Displacements and Duschinsky rotation of potential energy surfaces are included within the framework of a multidimensional harmonic oscillator model. This formalism gives a reliable description of the emission spectrum of Ir（ppy）3. The calculated results indicated that the 0→1 transition between the T1 state and the S0 state makes a large contribution to the emission spectrum, especially the vibrational modes below 1600 cm–1. The breathing vibration of the ligands and the CC and CN stretching vibrations of benzene and pyridine rings are the main reasons for the appearance of the shoulder peak in the spectrum. The Boltzmann distribution makes the intensities of both the main and the shoulder peaks decrease, and the peaks are close together. When coupled with first-principles density functional theory（DFT） calculations, the present approach appears to be an effective tool to obtain a quantitative description and detailed understanding of the spectra and photophysical processes of polyatomic molecules.