Complex between Formic Acid and Nitrous Oxide: A Matrix-Isolation and Computational Study

Abstract

The complex of formic acid (FA, HCOOH) with nitrous oxide (NO) was studied experimentally and computationally. Eight structures of the trans-FA···NO complex and nine structures of the cis-FA···NO complex were found at the density functional theory (M06-2X and wB97XD), MP2(full), and CCSD(T)-F12a levels. Two structures of the trans-FA···NO complex (1t and 3t) and two structures of the cis-FA···NO complex (1c and 3c) were identified by infrared spectroscopy in an argon matrix. Structure 1t with the bonded OH group appears in the matrices after deposition. Structures 3t and 3c with the free OH groups were prepared by vibrational excitation of the trans-FA conformer in structures 1t and 3t, respectively. Structure 3t is thermally unstable and relaxes to structure 1t at ∼15 K. Structure 1c with the bonded OH group is made by vibrational excitation of trans-FA monomer combined with thermal annealing. The lifetimes of the cis-FA···NO complex structures 1c (81.5 min) and 3c (18.7 min) in an argon matrix at 4.3 K are longer than that of cis-FA monomer (6.3 min). This difference agrees with the calculated stabilization barriers of these species.

Theoretical characterization of the photochemical reaction CO2 + O(3P) → CO + O2 related to experiments in solid krypton

“…The deposited samples show characteristic absorptions of matrix-isolated carbon dioxide and nitrous oxide molecules as reported previously [11][12][13]. A small amount of their aggregates is also present [14,15].…”

A tale of two conformers: spectroscopic evidence for halide catalysed formic acid isomerisation

“…Loosely bound intermolecular complexes between formic acid and other chemical partners have been studied extensively, 16,17 particularly neutral dimer complexes formed between formic acid and a host of molecular partners have been studied with small molecular partners including: water, [18][19][20][21] nitrogen, 22 formamide, 23 carbon dioxide, 24,25 carbon monoxide, 25 nitric acid, 26 acetonitrile, 27 and nitrous oxide. 28 A subset of these studies observed the intermolecular complex occuring between both the syn-formic acid and the higher energy anti-formic acid conformers. 21,22,24,28 In general, the strength of interaction in the anti-formic acid complexes was correlated with increased stability of the OH group, with the anti-formic acid-water complex appearing to be completely stabilised with respect to decay via proton tunnelling.…”

“…28 A subset of these studies observed the intermolecular complex occuring between both the syn-formic acid and the higher energy anti-formic acid conformers. 21,22,24,28 In general, the strength of interaction in the anti-formic acid complexes was correlated with increased stability of the OH group, with the anti-formic acid-water complex appearing to be completely stabilised with respect to decay via proton tunnelling. 21 Complexes formed between formic acid molecules and anion moieties have been studied to a lesser extent with anion complexes between formic acid and iodide, 29 and sulfur hexaflouride having been investigated using argon pre-dissociation spectroscopy, 30 as well as the formic acid dimer anion studied utilising both vibrational and photoelectron spectroscopy.…”

Weakly Bound Complex Formation between HCN and CH3Cl: A Matrix-Isolation and Computational Study

“…The formation of a weakly bound complex between HCN and CH 3 Cl ([(HCN) n CH 3 Cl]) was investigated using matrix-isolation FTIR spectroscopy coupled with quantum chemistry calculations. This technique has been used extensively to study weakly bound complexes in an argon matrix. − Briefly, the complexes are formed in an argon matrix at 10 K and detected by FTIR before and after annealing. The infrared spectrum is compared with simulated vibrational spectra based on optimized molecular geometries to identify the structure of the complex.…”