A theoretical study on the spectroscopy, structure, and stability of C2H3NS molecules

• Published in: Theoretical chemistry accounts Vol. 135; no. 9; pp. 1 - 12
• Main Authors: Gronowski, Marcin, Turowski, Michał, Custer, Thomas, Kołos, Robert
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2016; Springer Nature B.V
• Subjects: Anharmonicity; Atomic/Molecular Structure and Spectra; Chemistry; Chemistry and Materials Science; Clusters; Coupling (molecular); Electron states; Infrared absorption; Inorganic Chemistry; Isomers; Molecular structure; Organic Chemistry; Perturbation methods; Perturbation theory; Physical Chemistry; Regular Article; Relativistic effects; Rotational spectra; Structural stability; Theoretical and Computational Chemistry; Electronic states; Spectroscopy; Ab initio; Stability; Isomers; Thiocyanate
• ISSN: 1432-881X; 1432-2234
• DOI: 10.1007/s00214-016-1978-6

Here we report the results of a theoretical study devoted to the family of methyl thiocyanate (CH 3 –SCN) isomers. From among 14 species sharing the C 2 H 3 NS stoichiometry, the most thermodynamically stable of these are methyl isothiocyanate (CH 3 –NCS), methyl thiocyanate (CH 3 –SCN), and mercaptoacetonitrile (HS–CH 2 –CN). Energies were reliably predicted using the CCSD(T) variant of coupled-cluster calculations making use of a quadruple zeta-quality basis set. Minor contributions to the total energy, including scalar relativistic effects and extrapolation to the complete basis set limit, were obtained using second-order many-body perturbation theory. The three most stable isomers feature similar energy values (differing by few kJ/mol) that are much lower than those of the remaining C 2 H 3 NS species (more than 85 kJ/mol). Spectroscopic properties including rotational constants, anharmonic vibrational frequencies, infrared absorption intensities (harmonic), Raman activities, and the energies of excited electronic states have been derived using coupled-cluster or density functional theory for the whole set of C 2 H 3 NS molecules. Additionally, infrared absorption intensities and frequencies of overtone and combination bands are given for the three lowest energy isomers.