Weaker intermolecular forces expand the isomerization alternatives for molecular aggregation, as observed for the prototype models of the aniline trimer (An₃) and the monohydrated aniline dimer (An₂‐W) when compared to the phenol trimer. In this experiment the aniline clusters were generated in a jet‐cooled expansion and probed using broadband (chirped‐pulsed) microwave spectroscopy. Three isomers of the aniline trimer and two isomers of the hydrated dimer were detected and characterized in the rotational spectrum. In the homotrimer the weak N−H⋅⋅⋅N hydrogen bonds are assisted by subtle combinations of N−H⋅⋅⋅π and C−H⋅⋅⋅π interactions, producing several competing low‐lying ring species in the gas phase. One of the aniline trimers is a symmetric top, topologically equivalent to the only observed phenol trimer. Conversely, addition of a water molecule to the aniline dimer introduces a leading O−H⋅⋅⋅N interaction, making water to behave as dominant hydrogen‐bond pivot between the two aniline molecules. This combination of weak intermolecular interactions critically tests the performance of dispersion‐corrected or parametrized density‐functional methods. Evaluation of the B3LYP‐D3(BJ) and M06‐2X methods revealed deficiencies of the Truhlar functional to reproduce the experimental rotational data.

中文翻译：

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苯胺三聚体的异构性

如对苯胺三聚体（An ₃）和一水合苯胺二聚体（An ₂）的原型模型所观察到的，较弱的分子间作用力扩展了分子聚集的异构化替代方法。‐W）与酚三聚体相比。在该实验中，苯胺团簇是在喷气冷却的膨胀中生成的，并使用宽带（chi脉冲）微波光谱仪进行探测。检测了苯胺三聚体的三个异构体和水合二聚体的两个异构体，并在旋转光谱中进行了表征。在均三聚物中，NH-⋅⋅⋅π和CH-H⋅⋅⋅π相互作用的微妙组合有助于弱的NH-⋅·⋅N氢键，从而在气相中产生几种竞争性的低环物种。苯胺三聚体之一是对称的顶部，在拓扑学上等同于唯一观察到的苯酚三聚体。相反，在苯胺二聚体中添加水分子会引入领先的OH·⋅·N相互作用，使水表现为两个苯胺分子之间的主要氢键枢纽。弱分子间相互作用的这种组合严格测试了色散校正或参数化的密度泛函方法的性能。对B3LYP-D3（BJ）和M06-2X方法的评估揭示了Truhlar功能在再现实验旋转数据方面的缺陷。