氮杂环配体对卤化亚铜配合物发光机制影响的理论研究

Theoretical study on the effect of nitrogen heterocyclic ligands on the luminescence mechanism of cuprous halide complexes

为深入探讨卤化亚铜配合物的发光机制,运用密度泛函理论和含时密度泛函理论的计算方法研究了三个结构相似的溴化亚铜配合物(CuBr-py、CuBr-iq、CuBr-nap)。研究结果表明,CuBr-py和CuBr-nap,电子和空穴重叠程度小,导致其ΔE_(ST)较小;S_(1)与T_(1)间的重组能较小,使其可快速地完成反系间窜越过程,实现热活化延迟荧光(TADF)。此外,与CuBr-nap相比,CuBr-py自旋轨道耦合作用强,其磷光速率也较大,因此其具有TADF和磷光双通道发光特性。而CuBr-iq中喹啉环的存在增大了电子和空穴的重叠程度,ΔE_(ST)增大;同时S_(1)与T_(1)间的重组能较大,T_(1)无法顺利通过RISC过程回到S_(1),导致其最终呈现出磷光特性。这些理论计算结果与实验现象一致,且揭示了N杂环配体结构对于卤化亚铜配合物发光机制的影响规律,为设计和合成稳定高效的发光材料提供了有价值的理论指导。

In order to explore the luminescence mechanism of cuprous halide complexes,three cuprous bromide complexes(CuBr-py,CuBr-iq,CuBr-nap)were investigated with the use of density functional theory and time-dependent density functional theory.The results show that CuBr-py and CuBr-nap,with smallΔE ST owing to the little overlap of electron and hole as well as small recombination energy between S_(1) and T_(1),can quickly accomplish the reverse intersystem crossing and thus achieve thermally activated delayed fluorescence(TADF).In addition,compared with CuBr-nap,the strong spin-orbit coupling of CuBr-py leads to its larger phosphorescence rate,therefore,CuBr-py has TADF and phosphorescence dual-channel luminescence properties.However,the presence of quinoline ring in CuBr-iq increases the overlap of electron and hole,which increasesΔE ST;meanwhile,the recombination energy between S_(1) and T_(1) is larger,as a result,T_(1) cannot return to S_(1) successfully through the RISC process,and thus it presents the phosphorescence characteristics.The results of these theoretical calculations are consistent with the experimental phenomena,and reveal the influence of N heterocyclic ligand on the luminescence mechanism of copper halide complexes,which provides valuable theoretical guidance for the design and synthesis of stable and efficient luminescent materials.