Department of Physics, Durham University, South Road, Durham DH1 3LE, United Kingdom.
J Phys Chem Lett. 2023 Mar 23;14(11):2764-2771. doi: 10.1021/acs.jpclett.2c03925. Epub 2023 Mar 10.
The molecular photophysics in the thermally activated delayed fluorescence (TADF) spiro-acridine-anthracenone compound, ACRSA, is dominated by the rigid orthogonal spirocarbon bridging bond between the donor and acceptor. This critically decouples the donor and acceptor units, yielding photophysics, which includes (dual) phosphorescence and the molecular charge transfer (CT) states giving rise to TADF, that are dependent upon the excitation wavelength. The molecular singlet CT state can be directly excited, and we propose that supposed "spiro-conjugation" between acridine and anthracenone is more accurately an example of intramolecular through-space charge transfer. In addition, we show that the lowest local and CT triplet states are highly dependent upon spontaneous polarization of the environment, leading to energy reorganization of the triplet states, with the CT triplet becoming lowest in energy, profoundly affecting phosphorescence and TADF, as evident by a (thermally controlled) competition between reverse intersystem crossing and reverse internal conversion, i.e., dual delayed fluorescence (DF) mechanisms.
热激活延迟荧光 (TADF) 螺吖啶-蒽酮化合物 ACRSA 的分子光物理性质主要由供体和受体之间刚性正交的螺碳桥键决定。这使得供体和受体单元之间实现了关键性的去耦，产生了依赖于激发波长的光物理性质，包括（双）磷光和分子电荷转移 (CT) 态，从而导致 TADF。分子单重态 CT 态可以直接被激发，我们提出，假定的吖啶和蒽酮之间的“螺共轭”更准确地说是分子内通过空间电荷转移的例子。此外，我们表明，最低的局域和 CT 三重态高度依赖于环境的自发极化，导致三重态的能量重新排列，其中 CT 三重态的能量最低，这对磷光和 TADF 产生深远影响，这可以通过（热控制）反向系间窜跃和反向内转换之间的竞争来证明，即双延迟荧光 (DF) 机制。
