Suresh Subeesh Madayanad, Duda Eimantas, Hall David, Yao Zhen, Bagnich Sergey, Slawin Alexandra M Z, Bässler Heinz, Beljonne David, Buck Manfred, Olivier Yoann, Köhler Anna, Zysman-Colman Eli
Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, U.K. KY16 9ST.
Soft Matter Optoelectronics, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
J Am Chem Soc. 2020 Apr 8;142(14):6588-6599. doi: 10.1021/jacs.9b13704. Epub 2020 Mar 18.
An easy-to-access, near-UV-emitting linearly extended B,N-doped heptacene with high thermal stability is designed and synthesized in good yields. This compound exhibits thermally activated delayed fluorescence (TADF) at ambient temperature from a multiresonant (MR) state and represents a rare example of a non-triangulene-based MR-TADF emitter. At lower temperatures triplet-triplet annihilation dominates. The compound simultaneously possesses narrow, deep-blue emission with CIE coordinates of (0.17, 0.01). While delayed fluorescence results mainly from triplet-triplet annihilation at lower temperatures in THF solution, where aggregates form upon cooling, the TADF mechanism takes over around room temperature in solution when the aggregates dissolve or when the compound is well dispersed in a solid matrix. The potential of our molecular design to trigger TADF in larger acenes is demonstrated through the accurate prediction of Δ using correlated wave-function-based calculations. On the basis of these calculations, we predicted dramatically different optoelectronic behavior in terms of both Δ and the optical energy gap of two constitutional isomers where only the boron and nitrogen positions change. A comprehensive structural, optoelectronic, and theoretical investigation is presented. In addition, the ability of the achiral molecule to assemble on a Au(111) surface to a highly ordered layer composed of enantiomorphic domains of racemic entities is demonstrated by scanning tunneling microscopy.
我们设计并合成了一种易于获取、具有高热稳定性且能发射近紫外光的线性扩展硼氮掺杂并七苯，产率良好。该化合物在室温下从多共振（MR）态表现出热激活延迟荧光（TADF），是基于非三角烯的MR-TADF发射体的罕见实例。在较低温度下，三重态-三重态湮灭起主导作用。该化合物同时具有窄的深蓝色发射，CIE坐标为（0.17, 0.01）。虽然延迟荧光主要源于在四氢呋喃溶液中较低温度下的三重态-三重态湮灭，冷却时会形成聚集体，但当聚集体溶解或化合物在固体基质中良好分散时，TADF机制在溶液中室温左右起主导作用。通过基于相关波函数计算对Δ的准确预测，证明了我们分子设计在更大并苯中引发TADF的潜力。基于这些计算，我们预测了两种仅硼和氮位置不同的构造异构体在Δ和光学能隙方面显著不同的光电行为。本文进行了全面的结构、光电和理论研究。此外，通过扫描隧道显微镜证明了该非手性分子能够在Au(111)表面组装成由外消旋实体的对映体畴组成的高度有序层。
