High-energy irradiation of matrix isolated acetic acid yields a •CH3•••CO2 complex: A spectroscopic and ab initio study

被引：0

作者：

Zasimov, Pavel V. ^{[1
,2
]}

Tyurin, Daniil A. ^{[1
]}

Mirskoi, Georgii A. ^{[1
]}

Sanochkina, Elizaveta V. ^{[1
]}

Feldman, Vladimir I. ^{[1
]}

机构：

[1] Lomonosov Moscow State Univ, Dept Chem, Moscow 119991, Russia

[2] Free Univ Berlin, Inst Chem & Biochem Anorgan Chem, Fabeckstr 34-36, D-14195 Berlin, Germany

来源：

JOURNAL OF CHEMICAL PHYSICS | 2025年 / 162卷 / 07期

基金：

俄罗斯科学基金会;

关键词：

RADIATION-INDUCED TRANSFORMATIONS; ELECTRON-SPIN-RESONANCE; MULTIPLE-TRAPPING SITES; HIGH-RESOLUTION EPR; INFRARED-SPECTRUM; CARBOXYLIC-ACIDS; RADICAL CATIONS; NONCOVALENT INTERACTIONS; MONOCARBOXYLIC ACIDS; ORGANIC-MOLECULES;

D O I：

10.1063/5.0243092

中图分类号：

O64 [物理化学（理论化学）、化学物理学];

学科分类号：

070304 ; 081704 ;

摘要：

The mechanism of the chemical transformations of isolated small organic molecules induced by high-energy radiation is of basic interest for astrophysics and astrochemistry. In this work, we first applied a combination of electron paramagnetic resonance (EPR) and Fourier-transform infrared (FTIR) spectroscopy to identify the products of the radiation-induced transformations of isolated CH3COOH and CD3COOH molecules. As revealed by EPR, (CH3)-C-center dot (or (CD3)-C-center dot) is the principal primary radical generated from acetic acid in solid argon and xenon, while the FTIR results suggest that this radical is trapped mainly in the form of the (CH3)-C-center dot center dot center dot center dot CO2 radical-molecule complex. The assignment of this previously unknown complex was based on the complexation-induced shifts of the absorption bands corresponding to CH3OPLA and CO2bend vibration modes, confirmed by analysis of the kinetic curves, photochemical behavior, and comparison with the results of ab initio computations at the spin-unrestricted coupled-cluster singles, doubles, and perturbative triples level of theory. Most likely, the complex in matrices adopts the geometry close to the theoretically predicted structure with C-s symmetry stabilized by the C center dot center dot center dot C and O center dot center dot center dot H interactions. It was suggested that the complex could be produced via the intermediate formation of a CH3COOH+center dot radical cation deprotonating to the CH3COO center dot radical, which promptly decomposed to (CH3)-C-center dot + CO2 fragments. We believe that the results obtained in this study may contribute to a better understanding of the processing of acetic acid molecules in astrophysically relevant ices under high-energy irradiation and give a valuable insight into the understanding of weak intermolecular interactions involving radicals relevant to atmospheric chemistry, combustion, and carbon dioxide conversion.

引用

页数：14