Artigas Albert, Hagebaum-Reignier Denis, Carissan Yannick, Coquerel Yoann
Aix Marseille Université, CNRS, Centrale Marseille, ISM2 13397 Marseille France
Chem Sci. 2021 Sep 8;12(39):13092-13100. doi: 10.1039/d1sc03368a. eCollection 2021 Oct 13.
Electron delocalization in contorted polycyclic aromatic hydrocarbon (PAH) molecules was examined through 3D isotropic magnetic shielding (IMS) contour maps built around the molecules using pseudo-van der Waals surfaces. The resulting maps of electron delocalization provided an intuitive, yet detailed and quantitative evaluation of the aromatic, non aromatic, and antiaromatic character of the local and global conjugated cyclic circuits distributed over the molecules. An attractive pictural feature of the 3D IMS contour maps is that they are reminiscent of the Clar π-sextet model of aromaticity. The difference in delocalization patterns between the two faces of the electron circuits in contorted PAHs was clearly visualized. For π-extended contorted PAHs, some splits of the π system resulted in recognizable patterns typical of smaller PAHs. The differences between the delocalization patterns of diastereomeric chiral PAHs could also be visualized. Mapping IMS on pseudo-van der Waals surfaces around contorted PAHs allowed visualization of their superimposed preferred circuits for electron delocalization and hence their local and global aromaticity patterns.
通过使用伪范德华表面围绕扭曲的多环芳烃（PAH）分子构建的三维各向同性磁屏蔽（IMS）等高线图，研究了扭曲的多环芳烃分子中的电子离域。由此产生的电子离域图对分布在分子上的局部和全局共轭环电路的芳香性、非芳香性和反芳香性特征进行了直观、详细且定量的评估。三维IMS等高线图一个吸引人的图形特征是它们让人联想到芳香性的克拉尔π-六隅体模型。扭曲的多环芳烃中电子电路两个面之间离域模式的差异清晰可见。对于π扩展的扭曲多环芳烃，π体系的一些分裂导致了较小多环芳烃典型的可识别模式。非对映体手性多环芳烃离域模式之间的差异也可以可视化。在扭曲的多环芳烃周围的伪范德华表面上绘制IMS，可以可视化它们叠加的电子离域优先电路，从而可视化它们的局部和全局芳香性模式。
