Yang Peiqi, Pan Haoyang, Wang Yudi, Li Jie, Dong Yangyu, Wang Yongfeng, Hou Shimin
Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
Institute of Spin Science and Technology, South China University of Technology, Guangzhou 511442, China.
Molecules. 2024 Aug 12;29(16):3827. doi: 10.3390/molecules29163827.
Cyclo[n]carbon (C) is one member of the all-carbon allotrope family with potential applications in next-generation electronic devices. By employing first-principles quantum transport calculations, we have investigated the electronic transport properties of single-molecule junctions of C, with n = 14, 16, 18, and 20, connected to two bulk gold electrodes, uncovering notable distinctions arising from the varying aromaticities. For the doubly aromatic C and C molecules, slightly deformed complexes at the singlet state arise after bonding with one Au atom at each side; in contrast, the reduced energy gaps between the highest occupied and the lowest unoccupied molecular orbitals due to the orbital reordering observed in the doubly anti-aromatic C and C molecules lead to heavily deformed asymmetric complexes at the triplet state. Consequently, spin-unpolarized transmission functions are obtained for the Au-C-Au junctions, while spin-polarized transmission appears in the Au-C-Au junctions. Furthermore, the asymmetric in-plane π-type hybrid molecular orbitals of the Au-C-Au junctions contribute to two broad but low transmission peaks far away from the Fermi level (), while the out-of-plane π-type hybrid molecular orbitals dominate two sharp transmission peaks that are adjacent to , thus resulting in much lower transmission coefficients at compared to those of the Au-C-Au junctions. Our findings are helpful for the design and application of future cyclo[n]carbon-based molecular electronic devices.
环[n]碳（C）是全碳同素异形体家族的一员，在下一代电子设备中具有潜在应用。通过采用第一性原理量子输运计算，我们研究了n = 14、16、18和20的C单分子结与两个体相金电极相连时的电子输运性质，发现了因芳香性不同而产生的显著差异。对于双芳香性的C和C分子，在每侧与一个金原子键合后，单重态会出现轻微变形的复合物；相比之下，由于在双反芳香性的C和C分子中观察到的轨道重新排序，最高占据分子轨道和最低未占据分子轨道之间的能隙减小，导致三重态出现严重变形的不对称复合物。因此，Au-C-Au结获得了自旋非极化传输函数，而Au-C-Au结中出现了自旋极化传输。此外，Au-C-Au结的不对称面内π型杂化分子轨道在远离费米能级（）处贡献了两个宽但低的传输峰，而面外π型杂化分子轨道主导了与相邻的两个尖锐传输峰，因此与Au-C-Au结相比，处的传输系数要低得多。我们的研究结果有助于未来基于环[n]碳的分子电子器件的设计和应用。
