Characterization of the Azirinyl Cation and Its Isomers

详细信息    查看全文

• 作者：Sara I. L. Kokkila Schumacher ; Partha P. Bera ; Timothy J. Lee
• 刊名：Journal of Physical Chemistry A
• 出版年：2016
• 出版时间：March 3, 2016
• 年：2016
• 卷：120
• 期：8
• 页码：1275-1282
• 全文大小：353K
• ISSN：1520-5215

文摘

The azirinyl cation (C₂H₂N⁺) and its geometrical isomers could be present in the interstellar medium. The C₂H₂N⁺ isomers are, however, difficult to identify in interstellar chemistry because of the lack of high-resolution spectroscopic data from laboratory experiments. Ab initio quantum chemical methods were used to characterize the structures, relative energies, and spectroscopic and physical properties of the low energy isomers of the azirinyl cation. We have employed second-order Møller–Plesset perturbation theory (MP2), second-order Z-averaged perturbation theory (ZAPT2), and coupled cluster theory with singles and doubles with perturbative triples CCSD(T) methods along with large correlation consistent basis sets such as cc-pVTZ, cc-pCVTZ, cc-pVQZ, cc-pCVQZ, and cc-pV5Z. Harmonic vibrational frequencies, dipole moments, rotational constants, and proton affinities for the lowest energy isomers were calculated using the CCSD(T) method. Azirinyl cation, a cyclic isomer, is lowest in energy at all levels of theory employed. Azirinyl cation is followed by the cyanomethyl cation (H₂CCN)⁺, isocyanomethyl cation (H₂CNC)⁺, and a quasilinear HCCNH⁺ cation, which are 13.8, 17.3, and 21.5 kcal mol^–1 above the cyclic isomer, respectively, at the CCSD(T)/cc-pV5Z level of theory. The lowest three isomers all have C_2v symmetry and ¹A₁ ground electronic states. The quasilinear HCCNH⁺ cation has a C_s symmetry planar structure, and a ³A″ electronic ground state, unlike what some previous work suggested.