Lyu Yongkang, Cao Zhizheng, Zhang Fuliang, Cui Yonglin, Zhang Changzhe, Meng Qingtian
School of Physics and Electronics, Shandong Normal University, Jinan, Shandong 250358, China.
College of Chemistry and Materials Science, Ludong University, Yantai, Shandong 264025, China.
J Chem Phys. 2025 Jun 28;162(24). doi: 10.1063/5.0271666.
Cyclo[12]carbon (C12) is the smallest recently synthesized carbon ring molecule that conforms to Hückel anti-aromaticity. Unraveling the electronic structure and aromaticity differences between C12 and its isoelectronic analogs (B4C4N4, B6N6) is essential for elucidating the impact of C-atom bridging and the physicochemical properties of novel ring systems. Herein, robust first-principle computational methods (including static density functional theory calculations and ab initio molecular dynamics simulations) are employed to investigate the electronic populations, bonding features, and kinetic behavior of different electron types. The molecular aromaticity is also examined by using various analytical indicators, such as anisotropy of induced current density, ZZ component of isochemical shielding surfaces, electron localization function-π, and Fermi holes. It is revealed that C12 and B4C4N4 exhibit pronounced anti-aromatic properties, while B6N6 is non-aromatic. The distinct in-plane and out-of-plane π-orbital features and differences in electronic delocalization capacity are fundamental to their anti-aromatic and non-aromatic nature, contrasting with classical aromatic molecules such as C18. This work provides valuable references for understanding the electronic structures of novel carbon ring molecules and their isoelectronic analogs that lack aromaticity, which can aid in comprehending the physicochemical properties of classic main-group elements and advance the design and synthesis of new ring molecules.
环[12]碳（C₁₂）是最近合成的符合休克尔反芳香性的最小碳环分子。阐明C₁₂与其等电子类似物（B₄C₄N₄、B₆N₆）之间的电子结构和芳香性差异，对于阐明C原子桥连的影响以及新型环系统的物理化学性质至关重要。在此，采用了强大的第一性原理计算方法（包括静态密度泛函理论计算和从头算分子动力学模拟）来研究不同电子类型的电子布居、键合特征和动力学行为。还使用各种分析指标，如感应电流密度各向异性、等化学屏蔽表面的ZZ分量、电子定域函数-π和费米空穴，来检验分子的芳香性。结果表明，C₁₂和B₄C₄N₄表现出明显的反芳香性质，而B₆N₆是非芳香性的。其平面内和平面外π轨道特征的明显差异以及电子离域能力的不同，是它们反芳香和非芳香性质的基础，这与C₁₈等经典芳香分子形成对比。这项工作为理解缺乏芳香性的新型碳环分子及其等电子类似物的电子结构提供了有价值的参考，有助于理解经典主族元素的物理化学性质，并推动新型环分子的设计与合成。
