Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8551, Japan.
Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Aichi 464-8603, Japan.
Nat Commun. 2017 Jul 19;8:15984. doi: 10.1038/ncomms15984.
Aromaticity is a fundamental concept in chemistry. It is described by Hückel's rule that states that a cyclic planar π-system is aromatic when it shares 4n+2 π-electrons and antiaromatic when it possesses 4n π-electrons. Antiaromatic compounds are predicted to exhibit remarkable charge transport properties and high redox activities. However, it has so far only been possible to measure compounds with reduced aromaticity but not antiaromatic species due to their energetic instability. Here, we address these issues by investigating the single-molecule charge transport properties of a genuinely antiaromatic compound, showing that antiaromaticity results in an order of magnitude increase in conductance compared with the aromatic counterpart. Single-molecule current-voltage measurements and ab initio transport calculations reveal that this results from a reduced energy gap and a frontier molecular resonance closer to the Fermi level in the antiaromatic species. The conductance of the antiaromatic complex is further modulated electrochemically, demonstrating its potential as a high-conductance transistor.
芳香性是化学中的一个基本概念。它可以用休克尔规则来描述，该规则表明当一个环状平面π体系共享 4n+2 π电子时是芳香性的，而当它具有 4n π电子时是反芳香性的。反芳香化合物被预测具有显著的电荷输运性质和高氧化还原活性。然而，由于其能量不稳定性，迄今为止，仅有可能测量具有降低的芳香性的化合物，而不能测量反芳香性的物种。在这里，我们通过研究真正的反芳香化合物的单分子电荷输运性质来解决这些问题，表明与芳香性对应物相比，反芳香性导致电导增加了一个数量级。单分子电流-电压测量和从头算输运计算表明，这是由于反芳香性物种中的能隙减小和前沿分子共振更接近费米能级。反芳香性配合物的电导率可以进一步通过电化学方式进行调节，这表明它有可能成为一种高电导率晶体管。
