Effect of bromine substitution on blue phosphorescent trans -(N-heterocyclic carbene)Pt( ii ) acetylide complexes
Effect of bromine substitution on blue phosphorescent trans -(N-heterocyclic carbene)Pt( ii ) acetylide complexes
复制标题
溴取代对蓝色磷光反式-(N-杂环卡宾)Pt(ii)乙炔配合物的影响
DOI：
10.1039/d3dt01483e
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发表时间：
2023
影响因子：
4
通讯作者：
Schanze, Kirk S.
中科院分区：
文献类型：
--
作者：
Khan, Amran A.;Gobeze, Habtom B.;Islam, Tanjila;Arman, Hadi D.;Schanze, Kirk S.
反式-（NHC）2 PtII（CC-Ar）2（其中Ar =苯基或取代的苯基）类型的N-杂环卡宾络合物作为紫色和蓝色磷光体是令人感兴趣的。这些配合物在溶液和固体状态下都能发出有效的磷光，它们已被用作有机发光二极管中的磷光体。本研究探讨了溴取代对反式-（NHC）2 PtII（CC-Ar）2发色团的影响，通过一对配合物的电子物理研究，其中苯基的功能无论是3，5-二溴-或4-单溴-取代基（IPt-DB和IPt-MB，分别）。Br原子作为重原子引入，目的是增强自旋-轨道耦合并增加磷光三重态的辐射和非辐射衰减速率。IPt-MB和IPt-DB在溶液和PMMA基质中均表现出天蓝色磷光。有趣的是，与溶液中的IPt-DB相比，IPt-MB的发射量子产率和寿命显著较低。这种效应归因于单溴络合物中显著更大的非辐射衰减速率。结合DFT和TD-DFT计算，对两种配合物的热力学性质进行了分析，结果表明，两种配合物的热力学性质的差异与Br-取代基在苯乙炔环上的位置有关.简而言之，在IPt-MB中，Br-取代基位于Pt-CC-单元的对位，这在激发态产生更强的电子振动耦合，提高了非辐射衰减的速率。
N-heterocyclic carbene complexes of the type trans-(NHC)2PtII(CC–Ar)2 (where Ar = phenyl or substituted phenyl) are of interest as violet and blue phosphors. These complexes emit efficient phosphorescence in solution and in the solid state, and they have been applied as phosphors in organic light emitting diodes. This study explores the effect of bromine substitution on the trans-(NHC)2PtII(CC–Ar)2 chromophore through photophysical studies of a pair of complexes in which the phenyl groups feature either 3,5-dibromo- or 4-monobromo-substituents (IPt-DB and IPt-MB, respectively). The Br atoms were introduced as heavy atom(s) with the aim to enhance spin–orbit coupling and increase the radiative and non-radiative decay rates of the phosphorescent triplet state. Both IPt-MB and IPt-DB exhibit sky-blue phosphorescence in solution and in PMMA matrix. Interestingly, the emission quantum yield and lifetime of IPt-MB are substantially lower compared to IPt-DB in solution. This effect is attributed to a substantially larger non-radiative decay rate in the mono-bromo complex. Analysis of the photophysical data, combined with DFT and TD-DFT calculations, suggest that the difference in photophysical properties of the two complexes is related to the position of the Br-substituents on the phenyl acetylide rings. In short, in IPt-MB, the Br-substituents are located para-to the Pt-CC-unit, and this gives rise to stronger electron-vibrational coupling in the excited state, enhancing the rate of non-radiative decay.