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Formation and Evolution of H2C3O+• Radical Cations: A Computational and Matrix Isolation Study

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journal contribution
posted on 29.04.2022, 22:43 by Pavel V. Zasimov, Daniil A. Tyurin, Sergey V. Ryazantsev, Vladimir I. Feldman
The family of isomeric H2C3O+• 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 H2C3O+• from the C2H2···CO intermolecular complex and also considered the relative stability and monomolecular transformations of the H2C3O+• isomers through high-level ab initio calculations. The structures, energetics, harmonic frequencies, hyperfine coupling constants, and isomerization pathways for several of the most important H2C3O+• 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 C2H2···CO complex transforms into the E-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 H2CCCO+• isomer. Possible implications of the results and potentiality of the proposed synthetic strategy to the preparation of highly reactive organic radical cations are discussed.

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