桥连效应对空间电荷转移热激活延迟荧光分子激发态性质影响的理论研究  

Theoretical studies of the bridging effect on the excited-state properties of through space charge transfer-based thermally activated delayed fluorescence molecules

作　　者：邹雅彤 靳俊玲 夏思琪 ZOU Yatong;JIN Juning;XIA Siqi(College of Chemistry and Materials Engineering,Hunan University of Arts and Science,Changde 415000,China)

机构地区：[1]湖南文理学院化学与材料工程学院,湖南常德415000

出　　处：《湖南文理学院学报(自然科学版)》2025年第2期63-69,共7页Journal of Hunan University of Arts and Science(Science and Technology)

基　　金：湖南省大学生创新创业训练计划项目(湘教通[2022]174号,202210549012)。

摘　　要：本文使用密度泛函理论方法计算了3个具有空间电荷转移(TSCT)特征的热激活延迟荧光(TADF)分子XO、TF和XS的几何结构、单三态能级差(ΔE_(ST))、自旋轨道耦合常数(SOC)以及激发态衰减速率等数据,系统研究了桥连基团对这类染料分子TADF性能的影响。结果表明,桥连基团可明显影响几何和电子结构、跃迁特征和激发态性质。在基态下3个分子的给受体(D–A)呈面对面排列,最高占据分子轨道(HOMO)和最低空轨道(LUMO)均能较好分离。六元环桥连基团可导致更小的D–A距离(小于2.9?),存在明显的分子内弱相互作用。第一单重激发态(S_1)的电荷转移(CT)激发特征使3个分子具有较小的ΔE_(ST),S_1和最低三重激发态(T_1)不同的激发性质导致它们较强的SOC,因而反系间窜越速率(k_(RISC))提高,其中基于五元桥连基团的TF分子获得了最大的k_(RISC)(7.3×10~5s~(-1))。TSCT–TADF分子XO、TF和XS可同时实现快速荧光和延迟荧光,将有利于三重态激子的快速转换和降低效率滚降,可以作为良好的TADF材料。In this paper,the geometric structures,singlet-triplet energy difference(ΔEST),spin-orbit coupling constants(SOC)and the excited state decay rates of the thermally activated delayed fluorescence(TADF)molecules XO,TF and XS with through-space charge transfer(TSCT)feature were studied by density functional theory(DFT)methods to systematically investigate the effects of bridging groups on the TADF properties.The results show that the bridging groups greatly affect the geometric and electronic structure,transition characteristics and excited state properties.In the ground state,the donor-acceptor(D-A)are arranged face-to-face,and the HOMO-LUMO orbitals can be well separated.The six-membered bridging group induces a smaller D-A distance(less than 2.9Å),resulting in obvious weak intra-molecular interaction between D and A fragments.The charge transfer(CT)excitation characteristics of S1 endows the three molecules a smallΔEST,and the different excited-state nature between the S1 and T1 states leads to the strong spin-orbit coupling(SOC),eventuating in a high reverse intersystem crossing rate(kRISC),where molecule TF based on the five-membered bridging group obtains the largest kRISC(7.3×105 s-1).Molecules XO,TF and XS can simultaneously achieve fast prompt and delayed fluorescence,which enables the rapid conversion of triplet excitons and the reduction of efficiency roll-off,thus can act as good TADF materials.

关 键 词：热激活延迟荧光 激发态性质 反系间窜越 密度泛函理论 

分 类 号：O641[理学—物理化学]