Spectroscopic characterization of aminoacetonitrile, its ions and protonated aminoacetonitrile using quantum chemical methods

Abstract

We present theoretical vibrational and absorption spectra of aminoacetonitrile, its cation, anion, cyanoprotonated, and aminoprotonated aminoacetonitrile. We used second-order Moller-Plesset perturbation method (MP2) with TZVP basis set to obtain ground state geometries and vibrational spectra. Time dependent density functional theory method was used to obtain absorption spectra. Shifts in vibrational modes for aminoacetonitrile upon ionization and protonation are determined. The C:N stretching mode which is the most important mode in detection of nitriles in space is more intense in aminoacetonitrile ions and its two protonated form and is less IR active for neutral aminoacetonitrile. The nature of electronic transition for these molecules is identified. All the electronic transitions for neutral aminoacetonitrile and its cation are the r ! r* electronic transitions, whereas its anion and protonated aminoacetonitrile display the r ! r* as well as p ! p* transitions.

Formation of Negative Ions upon Dissociative Electron Attachment to the Astrochemically Relevant Molecule Aminoacetonitrile

“…Electron attachment to AAN is a purely dissociative process yielding production of six anionic fragments at m / z of 55 (C 2 H 3 N 2 – ), 54 (C 2 H 2 N 2 – ), 40 (C 2 H 2 N – ), 39 (C 2 HN – ), 26 (CN – ), and 16 (NH 2 – ). The possibility of a stable negatively charged AAN parent ion was previously predicted in calculations (MP2/TZVP), in which the EA value of 0.07 eV for the AAN molecule was obtained . In our experimental studies the parent anion NH 2 CH 2 CN – was not observed within the detection limit of the apparatus and also the W1BD calculations result in a negative adiabatic EA value for AAN of −0.85 eV.…”

“…Electron attachment to AAN is a purely dissociative process yielding production of six anionic fragments at m/z of 55 charged AAN parent ion was previously predicted in calculations (MP2/TZVP), in which the EA value of 0.07 eV for the AAN molecule was obtained. 29 In our experimental studies the parent anion NH 2 CH 2 CN − was not observed within the detection limit of the apparatus and also the W1BD calculations result in a negative adiabatic EA value for AAN of −0.85 eV. Due to this discrepancy between the results of our calculations and the ones from the earlier study, 29 we repeated the calculations at the MP2/TZVP level of theory.…”

“…All quantum chemical calculations have been carried out using the Gaussian 09 software. 28 29 In our experimental studies the parent anion NH2CH2CNwas not observed within the detection limit of the apparatus and also the W1BD calculations result in a negative adiabatic EA value for AAN of -0.85 eV. Due to this discrepancy between the results of our calculations and the ones from the earlier study, 29 we repeated the calculations at the MP2/TZVP level of theory.…”

“…29 In our experimental studies the parent anion NH 2 CH 2 CN − was not observed within the detection limit of the apparatus and also the W1BD calculations result in a negative adiabatic EA value for AAN of −0.85 eV. Due to this discrepancy between the results of our calculations and the ones from the earlier study, 29 we repeated the calculations at the MP2/TZVP level of theory. We obtained the same geometries of the neutral AAN molecules as well as the anion.…”

Insights into the molecular structure and infrared spectrum of the prebiotic species aminoacetonitrile

“…20 Moreover, the vibrational analysis is still ambiguous and suffers from a limited support by quantum chemistry, so far restricted to low-level calculations. [39][40][41] More generally, no study has properly addressed a complete structural and spectroscopic characterization of aminoacetonitrile using high-level quantum-chemical calculations. Here, we want to fill this gap and to expand the knowledge of the high-resolution rovibrational spectrum of aminoacetonitrile in the region between 500 and 1000 cm À1 .…”