Dipartimento di Chimica "Giacomo Ciamician", Università di Bologna, Via F. Selmi 2, 40126 Bologna, Italy.
Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy.
Phys Chem Chem Phys. 2022 Oct 5;24(38):23254-23264. doi: 10.1039/d2cp03294e.
Polycyclic aromatic hydrocarbons (PAHs) and polycyclic aromatic nitrogen heterocycles (PANHs) are important and ubiquitous species in space. However, their accurate structural and spectroscopic characterization is often missing. To fill this gap, we exploit the so-called "Lego brick" approach [Melli , , 2021, , 9904] to evaluate accurate rotational constants of some astrochemically relevant PAHs and PANHs. This model is based on the assumption that a molecular system can be seen as formed by smaller fragments for which a very accurate equilibrium structure is available. Within this model, the "template molecule" (TM) approach is employed to account for the modifications occurring when going from the isolated fragment to the molecular system under investigation, with the "linear regression" model being exploited to correct the linkage between different fragments. In the present work, semi-experimental equilibrium structures are used within the TM model. The performance of the "Lego brick" approach has been first tested for a set of small PA(N)Hs for which experimental data are available, thus leading to the conclusion that it is able to provide rotational constants with a relative accuracy well within 0.1%. Subsequently, it has been extended to the accurate prediction of the rotational constants for systems lacking any spectroscopic characterization.
多环芳烃（PAHs）和多环芳烃氮杂环（PANHs）是太空中重要且普遍存在的物质。然而，它们的准确结构和光谱特征通常是缺失的。为了填补这一空白，我们利用所谓的“乐高积木”方法[Melli 等人，2021 年，第 9904 页]来评估一些天化学相关的 PAHs 和 PANHs 的准确旋转常数。该模型基于这样的假设，即一个分子系统可以被视为由更小的片段组成，这些片段具有非常精确的平衡结构。在该模型中，采用“模板分子”（TM）方法来解释从孤立片段到所研究的分子系统时发生的变化，同时利用“线性回归”模型来校正不同片段之间的连接。在目前的工作中，在 TM 模型中使用了半实验平衡结构。首先，该“乐高积木”方法的性能已经针对一组具有实验数据的小的 PA（N）Hs 进行了测试，从而得出结论，它能够以 0.1%以内的相对精度提供旋转常数。随后，它被扩展到对缺乏任何光谱特征的系统的准确预测。
