Effect of hydrogen‐bonded interactions on the energetics and spectral properties of the astromolecule aminoacetonitrile

Abstract

A detailed and systematic electronic structure calculation has been performed to analyze the hydrogen-bonded interaction of aminoacetonitrile (H 2 NCH 2 CN) with hydrogen cyanide (HCN) andGlycine (H 2 NCH 2 COOH). Both HCN and aminoacetonitrile have already been detected in the interstellar medium (ISM) and their active role in the molecular mechanisms of glycine production has already been recognized. Four different density functional models have been used to study the effect of hydrogen bond formation on the energetic stability and vibrational spectra of the aminoacetonitrile-HCN and aminoacetonitrile-glycine complexes in gas phase. The aminoacetonitrile-glycine dimer is energetically far more stable than all forms of aminoacetonitrile-HCN dimers. Elastic and inelastic scattering of light off the hydrogen-bonded clusters have been investigated in details via Rayleigh and Raman spectroscopic parameters. The dipole moments and depolarization ratios are found to be sensitive on the type of hydrogen-bond network. The mean polarizabilty show appreciable dependence on the choice of the DFT-model. In general, all the chemical groups (OH, CN, NH 2 , and CH) that participate directly in the hydrogen bond formation suffer appreciable variation in the intensity of vibration. K E Y W O R D S hydrogen-bonded astromolecule, polarizability, Raman spectra, Rayleigh scattering, vibrational frequency shift 1 | I N TR ODU C TI ON Aminoacetonitrile (AAN) is a small organic compound that contains an amino group (NH 2 ) at one end and nitrile group (CN) at the other. The discovery of AAN in the constellation Sagittarius B2 (Sgr B2), in 2008, [1] is a significant event in astrochemistry, as it plays the central role in the Strecker amino acid synthesis mechanism. [2][3][4][5] Amino acids are the building blocks of proteins and, therefore, the key ingredients for the origin of life. The existence of amino acids in interstellar medium (ISM) has been a topic of interest for many years. As it is well known, the possible origin of life and its existence in interstellar space is an important aspect of exobiology and planetary chemistry. Among the 20 a-amino acids commonly found in proteins, glycine (GLY), with chemical formula NH 2 CH 2 COOH, is the simplest one. Although several attempts to detect the glycine have been carried out over the past few years, identification of isolated glycine is not firmly established yet. [6][7][8][9][10][11] In 2003, the interstellar glycine was reportedly identified in the hot molecular cores Sgr B2 (N-LMH), Orion KL, and W51 e1/e2. [10] But, the procedure of the assignment of the spectral lines used in this report suffered criticism. [11] However, the detection of GLY in the comet 81P/Wild 2 by NASA's Stardust mission in 2009 [12] brought new enthusiasm to the search of extraterrestrial amino acids. In 2016, Stardust results have been confirmed by the identification of volatile glycine along with methylamine and ethylamine in the shroud of gases surrounding the Comet 67P/Churyumov-Gerasimenko by the use ...

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