Zhang Zhen, Kumar Shiv, Bagnich Sergey, Spuling Eduard, Hundemer Fabian, Nieger Martin, Hassan Zahid, Köhler Anna, Zysman-Colman Eli, Bräse Stefan
Institute of Organic Chemistry (IOC), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany.
Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom.
Front Chem. 2020 Sep 30;8:563411. doi: 10.3389/fchem.2020.563411. eCollection 2020.
Six luminophores bearing an OBO-fused benzo[fg]tetracene core as an electron acceptor were designed and synthesized. The molecular structures of three molecules (PXZ-OBO, 5PXZ-OBO, 5DMAC-OBO) were determined by single crystal X-ray diffraction studies and revealed significant torsion between the donor moieties and the OBO acceptor with dihedral angles between 75.5 and 86.2°. Photophysical studies demonstrate that blue and deep blue emission can be realized with photoluminescence maxima (λ) ranging from 415 to 480 nm in mCP films. The emission energy is modulated by simply varying the strength of the donor heterocycle, the number of donors, and their position relative to the acceptor. Although the DMAC derivatives show negligible delayed emission because of their large singlet-triplet excited state energy difference, Δ , PXZ-based molecules, especially PXZ-OBO with an experimental Δ of 0.25 eV, demonstrate delayed emission in blend mCP films at room temperature, which suggests triplet exciton harvesting occurs in these samples, potentially by thermally activated delayed fluorescence.
设计并合成了六种带有OBO稠合苯并[fg]四苯核心作为电子受体的发光体。通过单晶X射线衍射研究确定了三种分子（PXZ-OBO、5PXZ-OBO、5DMAC-OBO）的分子结构，结果显示供体部分与OBO受体之间存在明显的扭转，二面角在75.5°至86.2°之间。光物理研究表明，在mCP薄膜中，光致发光最大值（λ）在415至480 nm范围内可实现蓝色和深蓝色发射。通过简单改变供体杂环的强度、供体的数量及其相对于受体的位置，可以调节发射能量。尽管由于DMAC衍生物的单重态-三重态激发态能量差Δ较大，其延迟发射可忽略不计，但基于PXZ的分子，尤其是实验测得Δ为0.25 eV的PXZ-OBO，在室温下的混合mCP薄膜中表现出延迟发射，这表明这些样品中发生了三重态激子俘获，可能是通过热激活延迟荧光实现的。
