An ab initio study of structure, stability, and spectroscopic parameters of 5-atomic [C, C, H, N, S] isomers

• Thioformyl cyanide is the lowest energy isomer among [C, C, H, N, S] species.
• Detailed predictions regarding the MW, IR and UV–VIS spectroscopy are presented.
• Predicted band strengths may permit the astronomical detection of selected isomers.
• The lowest energy [C, C, H, N, S] isomers are expected to be reasonably photostable.

This theoretical study is focused on predicting structures, energetics, and selected spectroscopic constants for a range of 5-atomic chemical species sharing the [C, C, H, N, S] stoichiometry, including thioformyl cyanide and iminoethenethione. An in-depth study carried out on the four most stable isomers have yielded (i) structures and energy for the lowest singlet and triplet excited electronic states; (ii) anharmonic vibrational frequencies and IR absorption intensities for the fundamental, overtone and combination modes; (iii) molecular parameters of interest to microwave spectroscopy: rotational constants, electric dipole moments, and quadrupole coupling constants.

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