School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland 4072, Australia.
Centre for Organic Photonics and Electronics, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
J Chem Phys. 2017 May 7;146(17):174305. doi: 10.1063/1.4981797.
Ligand substitution is often used for tuning the emission color of phosphorescent iridium(iii) complexes that are used in organic light-emitting diodes. However, in addition to tuning the emission color, the substituents can also affect the radiative and non-radiative decay rates of the excited state and hence the photoluminescence quantum yield. Understanding the substituent effect is therefore important for the design of new iridium(iii) complexes with specific emission properties. Using (time dependent) density functional methods, we investigate the substituent effect of n-propyl groups on the structure, emission color, and emission efficiency of fac-tris(1-methyl-5-phenyl-[1,2,4]triazolyl)iridium(iii) based phosphorescent complexes by comparing the calculated results for structural models with and without the n-propyl substituents. We find that attachment of the n-propyl groups increases the length of three Ir-N bonds, and although the emission color does not change significantly, the radiative and non-radiative rates do, leading to a prediction of enhanced blue phosphorescence emission efficiency. Furthermore, the calculations show that the attachment of the n-propyl groups leads to a larger activation energy to degradation and the formation of dark states.
配体取代通常用于调整磷光铱(III)配合物的发射颜色，这些配合物用于有机发光二极管。然而，除了调整发射颜色外，取代基还可以影响激发态的辐射和非辐射衰减速率，从而影响光致发光量子产率。因此，了解取代基效应对于设计具有特定发射特性的新型铱(III)配合物非常重要。使用（时变）密度泛函方法，我们通过比较带有和不带有正丙基取代基的结构模型的计算结果，研究了正丙基取代基对 fac-三（1-甲基-5-苯基-[1,2,4]三唑基）铱(III)基磷光配合物的结构、发射颜色和发射效率的取代基效应。我们发现，正丙基的引入增加了三个 Ir-N 键的长度，虽然发射颜色没有明显变化，但辐射和非辐射速率确实发生了变化，从而预测出增强的蓝色磷光发射效率。此外，计算表明，正丙基的引入导致更大的降解和暗态形成的活化能。
