ic8b01828_si_001.pdf (1.97 MB)
Quantum-Chemical Insights into the Phosphorescence Efficiencies of Blue-Emitting Platinum Complexes with Phenylene-Bridged Pincer Ligands
journal contribution
posted on 2018-09-20, 19:48 authored by Chongping Song, Jia Tang, Jiaqi Li, Zhixiang Wang, Ping Li, Houyu ZhangBlue phosphorescent
platinum complexes with phenylene-bridged pincer
ligands, [Pt(dmib)Cl] [1; dmib = m-bis(methylimidazolyl)benzene],
[Pt(mizb)Cl] [2; mizb = bis(N-methylimidazolium)benzene],
and [Pt(dpzb)Cl] [3; dpzb = m-bis(3,5-dimethylpyrazolyl)benzene],
have been investigated theoretically to rationalize the marked differences
of their phosphorescence efficiencies. On the basis of density functional
theory (DFT) and time-dependent DFT (TD-DFT) calculations, the geometrical
and electronic structures, absorption and emission properties, and
radiative and nonradiative processes are analyzed in detail. The emission
from the emissive lowest triplet state (T1) originates
from a mixture of metal-to-ligand charge-transfer (3MLCT)
and intraligand charge-transfer (3ILCT) states. The calculated
radiative decay rate constants of T1 of the complexes are
comparable and in the same order of magnitude with the experimental
measurements. Therefore, the potential energy profiles for the deactivation
processes from T1 via temperature-independent and -dependent
pathways are explored to reveal the effect of nonradiative decay on
phosphorescence. The calculated results indicate that the very weak
emission of 3 could be ascribed to the deactivation process
via the metal-centered (3MC) state, which can be readily
accessible via a spontaneous process from the T1 state.
This work provides more in-depth insight into the nature of the emissive
excited state, shielding light on a better understanding of the excited-state
behavior of phosphorescent platinum complexes.