Armon Amit Manor, Bedi Anjan, Borin Veniamin, Schapiro Igor, Gidron Ori
Institute of Chemistry The Hebrew University of Jerusalem Jerusalem 9190401 Israel.
Department of Chemistry SRM Institute of Science and Technology Kattankulathur 603203 Tamil Nadu India.
European J Org Chem. 2021 Oct 21;2021(39):5424-5429. doi: 10.1002/ejoc.202100865. Epub 2021 Oct 19.
Polycyclic aromatic hydrocarbons (PAHs) are widely used in organic electronic devices. The electronic, magnetic, and optical properties of PAHs can be tuned by structural modifications to the aromatic backbone to introduce an inherent distortion from planarity, such as bending or twisting. However, it remains difficult to isolate and control the effects of such distortions. Here, we sought to understand how backbone twisting and bending affect the electronic properties of acenes, as models for larger PAHs. We found that, even when highly distorted from planarity (30° per ring), acenes maintain their aromatic character and π orbital delocalization with minor mixing of the σ and π orbitals. In addition, the energy gap between the HOMO and LUMO decreases with increasing twist, while the gap is hardly affected by bending, since the energy of both orbitals increase to a similar extent. For bent acenes in the triplet state, the spin becomes more localized with increasing bend, whereas twisting produces an evenly distributed spin delocalization. These findings can guide the synthesis of PAHs with tailored properties.
多环芳烃（PAHs）广泛应用于有机电子器件中。通过对芳香主链进行结构修饰以引入与平面性的固有畸变，如弯曲或扭曲，可以调节PAHs的电子、磁性和光学性质。然而，分离和控制这种畸变的影响仍然很困难。在这里，我们试图了解主链扭曲和弯曲如何影响并苯的电子性质，作为更大PAHs的模型。我们发现，即使与平面性高度畸变（每个环30°），并苯仍保持其芳香特性和π轨道离域，同时σ和π轨道有少量混合。此外，HOMO和LUMO之间的能隙随着扭曲增加而减小，而该能隙几乎不受弯曲影响，因为两个轨道的能量增加程度相似。对于处于三重态的弯曲并苯，随着弯曲增加自旋变得更加局域化，而扭曲则产生均匀分布的自旋离域。这些发现可以指导具有定制性质的PAHs的合成。
