Arpa Enrique M, Stafström Sven, Durbeej Bo
Division of Theoretical Chemistry, IFM, Linköping University, 58183 Linköping, Sweden.
Institute of Organic Chemistry, RWTH Aachen University, 52056 Aachen, Germany.
J Org Chem. 2025 Jan 24;90(3):1297-1308. doi: 10.1021/acs.joc.4c02475. Epub 2025 Jan 15.
The harmonic oscillator model of aromaticity (HOMA) offers a straightforward route to quantifying aromaticity that requires no other information than the bond lengths of the conjugated ring in question. Given that such information is often readily obtainable from quantum-chemical calculations, it is pertinent to improve this parametrized model as much as possible. Here, a new version of HOMA is presented where, atypically, the corresponding parameters are derived from the actual bond lengths of both aromatic and antiaromatic (rather than nonaromatic) reference compounds, as calculated with a high-level method. The resulting model, which we denote HOMAc, covers CC, CN, NN, and CO bonds and is tested at eight different levels of theory for 45 (single-ring, multi-ring, carbocyclic, N,O-heterocyclic) molecules across the aromatic-antiaromatic spectrum. Thereby, it is found that HOMAc provides a description of aromaticity and antiaromaticity in better accord with magnetic, energetic, and π-delocalization-based reference data than does the standard parametrization of HOMA. Altogether, the results highlight the possibility to realize more reliable geometry-based probing of (anti)aromaticity with the use of HOMAc and with substantial freedom in the choice of quantum-chemical method.
芳香性的谐振子模型（HOMA）提供了一条量化芳香性的直接途径，该途径除了所讨论共轭环的键长之外不需要其他任何信息。鉴于此类信息通常很容易从量子化学计算中获得，尽可能改进这个参数化模型是恰当的。在此，提出了一个新版本的HOMA，不同寻常的是，相应参数是从使用高级方法计算得到的芳香族和反芳香族（而非非芳香族）参考化合物的实际键长中推导出来的。由此得到的模型，我们称之为HOMAc，涵盖了C-C、C-N、N-N和C-O键，并在八种不同的理论水平下对45个（单环、多环、碳环、N、O-杂环）跨越芳香-反芳香光谱的分子进行了测试。结果发现，与HOMA的标准参数化相比，HOMAc对芳香性和反芳香性的描述与基于磁性、能量和π离域的参考数据更相符。总之，这些结果突出了利用HOMAc并在量子化学方法的选择上有很大自由度来实现对（反）芳香性进行更可靠的基于几何结构探测的可能性。
