Supplementary information files for Elucidating the electronic structure of a delayed fluorescence emitter via orbital interactions, excitation energy components, charge-transfer numbers, and vibrational reorganization energies

Supplementary files for article Elucidating the electronic structure of a delayed fluorescence emitter via orbital interactions, excitation energy components, charge-transfer numbers, and vibrational reorganization energies. Recently, Wang and co-workers carried out frontier molecule orbital engineering in the design of m-Cz-BNCz, a thermally activated delayed fluorescence (TADF) molecule that emits pure green light at an external quantum efficiency of 27%. To further understand the underlying molecular design principles, we employed four advanced electronic structure analysis tools. First, an absolutely localized molecular orbitals (ALMO-) based analysis indicates an antibonding combination between the highest occupied molecular orbitals (HOMOs) of the donor 3,6-di-tert-butylcarbazole fragment and the acceptor BNCz fragment, which raises the HOMO energy and red-shifts the fluorescence emission wavelength. Second, excitation energy component analysis reveals that the S1-T1 gap is dominated by two-electron components of the excitation energies. Third, charge transfer number analysis, which is extended to use fragment-based Hirshfeld weights, indicates that the S1 and T1 excited states of m-Cz-BNCz (within time-dependent density functional theory) have notable charge transfer characters (27% for S1 and 12% for T1). This provides a balance between a small single-triplet gap and a substantial fluorescence intensity. Last, a vibrational reorganization energy analysis pinpoints the torsional motion between the BNCz and Cz moieties of m-Cz-BNCz as the source for its wider emission peak than that of p-Cz-BNCz. These four types of analyses are expected to be very valuable in the study and design of other TADF and functional dye molecules.

补充文章《通过轨道相互作用、激发能成分、电荷转移数和振动重组能量阐明延迟荧光发射体的电子结构》的辅助文件。近期，王及其同事们在设计m-Cz-BNCz这种热激活延迟荧光（TADF）分子时，对其前沿分子轨道进行了精心设计，该分子能够以27%的外部量子效率发射纯净的绿色光。为了进一步阐释其背后的分子设计原理，我们运用了四种先进的电子结构分析方法。首先，基于绝对局域分子轨道（ALMO-）的分析揭示了供体3,6-二叔丁基咔唑片段的最高占据分子轨道（HOMOs）与受体BNCz片段之间的反键组合，这提升了HOMO能量并使荧光发射波长红移。其次，激发能成分分析表明，S1-T1能隙主要由激发能的两电子成分主导。第三，电荷转移数分析（扩展至基于片段的Hirshfeld权重）表明，在时间相关密度泛函理论下，m-Cz-BNCz的S1和T1激发态具有显著的电荷转移特性（S1为27%，T1为12%），这提供了小单重-三重态能隙与显著荧光强度的平衡。最后，振动重组能量分析确定了m-Cz-BNCz中BNCz和Cz部分之间的扭转运动是其发射峰比p-Cz-BNCz更宽的原因。这四种分析类型预计将对其他TADF和功能性染料分子的研究和设计具有极高的价值。