Matrix isolation and ab initio study on HCN/CO2 system and its radiation-induced transformations: Spectroscopic evidence for HCN⋯CO2 and trans-HCNH⋯CO2 complexes

Svetlana V Kameneva; Daniil A Tyurin; Kirill B Nuzhdin; Vladimir I Feldman

doi:10.1063/1.4969075

Matrix isolation and ab initio study on HCN/CO₂ system and its radiation-induced transformations: Spectroscopic evidence for HCN⋯CO₂ and trans-HCNH⋯CO₂ complexes

J Chem Phys. 2016 Dec 7;145(21):214309. doi: 10.1063/1.4969075.

Authors

Svetlana V Kameneva¹, Daniil A Tyurin¹, Kirill B Nuzhdin¹, Vladimir I Feldman¹

Affiliation

¹ Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia.

PMID: 28799372
DOI: 10.1063/1.4969075

Abstract

Spectroscopic characteristics and X-ray induced transformations of the HCN⋯CO₂ complex in solid Ar and Kr matrices were studied by FTIR spectroscopy and ab initio calculations at the CCSD(T) level. The complex was prepared by deposition of the HCN/CO₂/Ng gas mixtures (Ng = Ar or Kr). The comparison of the experiment and calculations prove formation of a linear, H-bonded NCH⋯OCO complex with a substantial red shift of the C-H stretching band and a blue shift of the H-C-N bending band in respect to the monomer. This result is in contrast with the previous gas-phase observations, where only T-shape complex was found. Irradiation of deposited matrices leads to formation of CN radicals and HNC molecules and subsequent annealing results in appearance of H₂CN and trans-HCNH in both matrices plus HKrCN in the case of Kr. In the presence of CO₂, the strongest absorption of trans-HCNH radical demonstrates an additional blue-shifted (by 6.4 cm^-1) feature, which was assigned to the N-coordinated complex of this radical with CO₂ on the basis of comparison with calculations. To our knowledge, it is the first experimentally observed complex of this radical. No evidence was found for HKrCN⋯CO₂ complex, which was explained tentatively by steric hindrance.