Stanger Amnon
Schulich Department of Chemistry , Technion , Haifa 32000 , Israel.
J Phys Chem A. 2019 May 2;123(17):3922-3927. doi: 10.1021/acs.jpca.9b02083. Epub 2019 Apr 18.
Applying fine grids of nucleus independent chemical shift (NICS) probes (BQs) at different distances from the molecular plane of aromatic and antiaromatic molecules suggests that, at short distances, NICS is maximal (absolute values) off the geometrical center of the systems. In nonsymmetric systems, the center of the induced ring current may be a little off the geometrical center, but the difference is negligible at distances ≥2 Å. At these distances, the change of NICS with the distance from the ring follows a power relation. It is shown that the order of diatropicity and paratropicity within a group of molecules depends on the distance from the system (namely, the order of NICS( r) depends on r). It is thus suggested to use ∫NICS as a quantitative measure of aromaticity.
在距芳香族和反芳香族分子分子平面不同距离处应用精细的核独立化学位移（NICS）探针（BQs）网格表明，在短距离时，NICS在体系几何中心之外达到最大值（绝对值）。在非对称体系中，感应环电流的中心可能会稍微偏离几何中心，但在距离≥2 Å时差异可忽略不计。在这些距离下，NICS随距环的距离变化遵循幂关系。结果表明，一组分子内的抗磁各向异性和顺磁各向异性顺序取决于距体系的距离（即，NICS(r)的顺序取决于r）。因此建议使用∫NICS作为芳香性的定量度量。
