Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia.
Center for Energy Science and Technology, Skolkovo Institute of Science and Technology, 121205 Moscow, Russia.
J Am Chem Soc. 2022 May 11;144(18):8115-8128. doi: 10.1021/jacs.2c00295. Epub 2022 Apr 29.
The family of isomeric HCO radical cations is of great interest for physical organic chemistry and chemistry occurring in extraterrestrial media. In this work, we have experimentally examined a unique synthetic route to the generation of HCO from the CH···CO intermolecular complex and also considered the relative stability and monomolecular transformations of the HCO isomers through high-level calculations. The structures, energetics, harmonic frequencies, hyperfine coupling constants, and isomerization pathways for several of the most important HCO isomers were calculated at the UCCSD(T) level of theory. The complementary FTIR and EPR studies in argon matrices at 5 K have demonstrated that the ionized CH···CO complex transforms into the -HCCHCO isomer, and this latter species is supposed to be the key intermediate in further chemical transformations, providing a remarkable piece of evidence for kinetic control in low-temperature chemistry. Photolysis of this species at λ = 410-465 nm results in its transformation to the thermodynamically most stable HCCCO isomer. Possible implications of the results and potentiality of the proposed synthetic strategy to the preparation of highly reactive organic radical cations are discussed.
HCO 自由基阳离子的异构体家族对于物理有机化学和天体介质中发生的化学具有重要意义。在这项工作中，我们通过实验研究了一种独特的合成途径，从 CH···CO 分子间复合物中生成 HCO，并且通过高级计算考虑了 HCO 异构体的相对稳定性和单分子转化。在 UCCSD(T)理论水平上计算了几种最重要的 HCO 异构体的结构、能量、简正频率、超精细耦合常数和异构化途径。在 5 K 的氩基质中的互补 FTIR 和 EPR 研究表明，离解的 CH···CO 复合物转化为 -HCCHCO 异构体，并且后者被认为是进一步化学转化的关键中间体，为低温化学中的动力学控制提供了显著的证据。该物质在 λ = 410-465nm 处的光解导致其转化为热力学上最稳定的 HCCCO 异构体。讨论了结果的可能意义和所提出的合成策略对于制备高反应性有机自由基阳离子的潜力。
