Monaco Guglielmo, Zanasi Riccardo
Department of Chemistry and Biology "A. Zambelli", University of Salerno , via Giovanni Paolo II 132, Fisciano (SA) 84084, Italy.
J Phys Chem Lett. 2017 Oct 5;8(19):4673-4678. doi: 10.1021/acs.jpclett.7b01937. Epub 2017 Sep 14.
[10]Cyclophenacene is an important synthetic target that shows a pair of nucleus-independent chemical shift (NICS) values for the center of mass and six-membered rings typical of an aromatic species. This is found in contrast with the global paratropic current density induced by a magnetic field parallel to the main symmetry axis. This apparent contradiction has been analyzed by studying the tensor character of the magnetic response. It turns out that the molecule displays two characters, one paratropic (antiaromatic) and another one diatropic (aromatic), depending on the orientation of the inducing magnetic field. The paratropic response, which cannot be recognized from the NICS values, is associated with a well-defined destabilization of the belt closure, as witnessed by homodesmotic reactions. A scalar measure of magnetic aromaticity, the field-independent current strength, has been introduced, which allows us to reach the conclusion that [10]cyclophenacene is indeed an aromatic molecule, although it is significantly affected by the paratropic response.
[10]环菲是一个重要的合成目标，其质心和六元环显示出一对典型芳香族物种的与核无关的化学位移（NICS）值。这与平行于主对称轴的磁场诱导的全局抗磁电流密度形成对比。通过研究磁响应的张量特性分析了这种明显的矛盾。结果表明，根据感应磁场的方向，该分子表现出两种特性，一种是抗磁的（反芳香性），另一种是顺磁的（芳香性）。从NICS值无法识别的抗磁响应与环闭合的明确不稳定相关，同系反应证明了这一点。引入了一种与场无关的电流强度的磁芳香性标量度量，这使我们能够得出结论，[10]环菲确实是一个芳香分子，尽管它受到抗磁响应的显著影响。
