Conformational Landscapes and Infrared Spectra of Gas-phase Interstellar Molecular Clusters [(C₃H₃N)(CH₃OH)_n, n = 1–4]

Abstract

Acrylonitrile (A) is one of the important interstellar molecules, which is considered closely related to the origin of life. And methanol (M) is one of the commonly used solvents, which is also found in outer space. Herein, we obtained the infrared (IR) spectra of size-selected AM n (n = 1–4) clusters in supersonic jet by monitoring their fragments of H+AM n–1 (n = 1–4) with vacuum ultraviolet single-photon soft ionization/IR-depletion technique. IR spectra of AM n (n = 1–4) clusters were recorded in the CH and OH vibration bands in the range of 2700–3800 cm–1. Spectra of AM n (n = 1–4) clusters are similar in the CH stretching regions, while those show significant variations in the OH stretching regions with the increase of methanol molecules. Calculated IR spectra, which were predicted with the B3LYP-D3­(BJ)/aug-cc-pVDZ method, were employed to compare with the experimental results. For AM, AM2, and AM3, the structures with the methanol cyclic hydrogen bonded with [N1–C4­(H6)] of acrylonitrile are more stable than the other H-bonded structures. For the most stable structures of AM4, however, the results show that the acrylonitrile is binding to a H-bonded ring formed by OH groups of four methanol molecules. The AM, AM2, and AM3 conformers with the single ring on the C 1 side of acrylonitrile, such as C 1-AM-a, C 1-AM2-a, and C 1-AM3-a, are dominant in the gas phase, while the C 2-AM4-a conformer with the H-bonded ring formed by the OH groups on the C 2 side of acrylonitrile is more stable than that of CM4-A-a in our experimental conditions (>130 K). These findings may provide valuable insight into the microsolvation process of the interstellar molecules and other biomolecules in gas phase.

Proton Transfer in Nitromethane–Ammonia Clusters under VUV Single-Photon Ionization Explored by Infrared Spectroscopy and Theoretical Calculations

“…In this experiment, the molecular beam temperature is estimated as ca. 100–150 K, − , and the proportions of the three isomers are about 74.36, 25.64, and 0.00%, respectively. This may indicate that the most populated conformer of the neutral cluster is (CH 3 NO 2 -NH 3 )-I, which contains three intermolecular hydrogen bonds.…”

“…IR spectra of neutral and cationic gas-phase clusters of CH 3 NO 2 -NH 3 were observed in this experiment. The detailed experimental setups have been described previously; − only a brief description is given here. Gas-phase CH 3 NO 2 -NH 3 clusters are generally produced in supersonic jet expansion. − The mixture of ammonia and helium (He) was used as the carrier gas, and the concentration of ammonia is 5%.…”

A Facile Route for the Formation of Complex Nitrogen-Containing Prebiotic Molecules in the Interstellar Medium

“…To determine the detailed process of the Michael addition reaction of the ionized AN–CH 3 OH cluster, reaction path search calculations were carried out by using the GRRM method. Figure shows the energy diagram of the reaction processes of the vertically ionized AN–CH 3 OH cluster from the three neutral isomers which have been found in our previous study . After the ionization of n1 and n2 structures, the proton of the OH bond of CH 3 OH transfers to the N atom of AN directly (to form b5 ).…”

Spectroscopic evidence of S∴N and S∴O hemibonds in heterodimer cations

“…In this study, the infrared spectra of gaseous [CH 3 SH–NH 3 ] + , [CH 3 SCH 3 –NH 3 ] + , [CH 3 SCH 3 –H 2 O] + and [CH 3 OCH 3 –H 2 O] + clusters were recorded by infrared laser pre-dissociation spectroscopy using a time-of-flight mass spectrometer (TOF-MS) and one-photon ionization with vacuum ultraviolet (VUV) light. The experimental setup has been described in our previous studies in detail 49–51 and only a brief introduction is provided here. Gaseous samples, such as CH 3 SH, CH 3 OCH 3 , and NH 3 , were premixed with the helium carrier gas in a ratio of ∼1 : 100, respectively, at a pressure of ∼2 atm.…”