Kumar Chandan, Fliegl Heike, Sundholm Dage
Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo , P. O. Box 1033, N-1315 Blindern, Norway.
Department of Chemistry, University of Helsinki , P.O. Box 55, A. I. Virtanens Plats 1, FIN-00014 Helsinki, Finland.
J Phys Chem A. 2017 Sep 28;121(38):7282-7289. doi: 10.1021/acs.jpca.7b07607. Epub 2017 Sep 15.
Magnetically induced ring-current strength susceptibilities and nucleus independent chemical shifts (NICS) have been studied for 15 single-ring aromatic, antiaromatic, and nonaromatic molecules. The current densities have been calculated at the density functional theory (DFT), Hartree-Fock (HF) theory, and second-order Møller-Plesset perturbation theory (MP2) levels using the gauge-including magnetically induced current method (GIMIC). The ring-current strength susceptibilities have been obtained by numerical integration of the current density flowing around the molecular ring. The calculated ring-current strength susceptibilities are almost independent of the level of theory. The relative degree of aromaticity deduced from the magnetic properties has been compared with the ones deduced from hydrogenation enthalpies that are considered to be proportional to aromatic stabilization energies (ASE). For the studied single-ring molecules, GIMIC, NICS, and ASE calculations yield similar trends. The study shows that there is a linear correlation between the magnetic and energetic criteria of aromaticity. The largest uncertainty originates from the accuracy of the energy data, because they are much more dependent on the employed computational level than the calculated magnetic properties. Thus, ring-current strength susceptibilities can be used for assessing the degree of aromaticity.
已对15个单环芳香、反芳香和非芳香分子的磁感应环电流强度磁化率和核独立化学位移（NICS）进行了研究。使用含规范磁感应电流方法（GIMIC）在密度泛函理论（DFT）、哈特里-福克（HF）理论和二阶莫勒-普列斯特定则微扰理论（MP2）水平上计算了电流密度。通过对分子环周围流动的电流密度进行数值积分得到环电流强度磁化率。计算得到的环电流强度磁化率几乎与理论水平无关。将由磁性性质推导的芳香性相对程度与由氢化焓推导的相对程度进行了比较，氢化焓被认为与芳香稳定化能（ASE）成正比。对于所研究的单环分子，GIMIC、NICS和ASE计算得出相似的趋势。该研究表明，芳香性的磁性和能量标准之间存在线性相关性。最大的不确定性源于能量数据的准确性，因为它们比计算得到的磁性性质更依赖于所采用的计算水平。因此，环电流强度磁化率可用于评估芳香性程度。
