Hermann Mathias, Böttcher Tobias, Schorpp Marcel, Richert Sabine, Wassy Daniel, Krossing Ingo, Esser Birgit
Institute for Organic Chemistry, University of Freiburg, Albertstraße 21, 79104, Freiburg, Germany.
Institute for Inorganic and Analytical Chemistry, University of Freiburg, Albertstraße 21, 79104, Freiburg, Germany.
Chemistry. 2021 Mar 12;27(15):4964-4970. doi: 10.1002/chem.202005131. Epub 2021 Feb 12.
Dibenzo[a,e]pentalene (DBP) is a non-alternant conjugated hydrocarbon with antiaromatic character and ambipolar electrochemical behavior. Upon both reduction and oxidation, it becomes aromatic. We herein study the chemical oxidation and reduction of a planar DBP derivative and a bent DBP-phane. The molecular structures of its planar dication, cation radical and anion radical in the solid state demonstrate the gained aromaticity through bond length equalization, which is supported by nucleus independent chemical shift-calculations. EPR spectra on the cation radical confirm the spin delocalization over the DBP framework. A similar delocalization was not possible in the reduced bent DBP-phane, which stabilized itself by proton abstraction from a solvent molecule upon reduction. This is the first report on structures of a DBP cation radical and dication in the solid state and of a reduced bent DBP derivative. Our study provides valuable insight into the charged species of DBP for its application as semiconductor.
二苯并[a,e]戊搭烯（DBP）是一种具有反芳香性和双极性电化学行为的非交替共轭烃。在还原和氧化时，它都会变成芳香性的。我们在此研究了一种平面DBP衍生物和一种弯曲的DBP-环的化学氧化和还原。其平面二价阳离子、阳离子自由基和阴离子自由基在固态下的分子结构通过键长均等化展示了获得的芳香性，这得到了核独立化学位移计算的支持。阳离子自由基的电子顺磁共振光谱证实了自旋在DBP骨架上的离域。在还原的弯曲DBP-环中不可能有类似的离域，它在还原时通过从溶剂分子中夺取质子而自身稳定下来。这是关于固态下DBP阳离子自由基和二价阳离子以及还原的弯曲DBP衍生物结构的首次报道。我们的研究为DBP作为半导体的应用中其带电物种提供了有价值的见解。
