Alves Rodolpho L R, Leitão Ezequiel F V, Ventura E, do Monte S A
Departamento de Química, CCEN, Universidade Federal da Paraíba, João Pessoa, Brazil.
Unidade Acadêmica de Ciências Exatas e da Natureza, Universidade Federal de Campina Grande, Cajazeiras, Brazil.
J Comput Chem. 2025 Mar 30;46(8):e70079. doi: 10.1002/jcc.70079.
Normally, carbocations and carbanions of hydrocarbons react to form a CC σ bond. However, if the ions are very stable with a large steric repulsion between them, one can also have the formation of an ion pair, generally much less stable than the covalent form. For an extremely large steric repulsion in the covalent form, the ion pair can become the most stable form, even in the gas phase. DFT and CASSCF calculations indicate that the tert-butylfulleride anion and the tris[1-(5-isopropyl-3,8-dimethylazulenyl)]-cyclopropenylium cation form an ion pair. This is the first study of this ion pair, although it is the building block of a salt that has already been synthesized. DFT results indicate that this ion pair is considerably more stable than its covalent counterpart. Nevertheless, several properties of the ionic and covalent forms are similar. An energy decomposition analysis indicates the polarization, electrostatic, and dispersion terms as the most important attractive terms between the ions.
通常情况下，烃类的碳正离子和碳负离子会发生反应形成CC σ键。然而，如果离子非常稳定且它们之间存在很大的空间排斥力，那么也可能形成离子对，其稳定性通常比共价形式低得多。对于共价形式中存在极大空间排斥力的情况，即使在气相中，离子对也可能成为最稳定的形式。密度泛函理论（DFT）和完全活性空间自洽场（CASSCF）计算表明，叔丁基富勒烯阴离子和三[1-(5-异丙基-3,8-二甲基薁基)]-环丙烯鎓阳离子形成了离子对。这是对该离子对的首次研究，尽管它是一种已合成盐的结构单元。DFT结果表明，该离子对比其共价形式稳定得多。然而，离子形式和共价形式的一些性质是相似的。能量分解分析表明，极化、静电和色散项是离子之间最重要的吸引项。
