Ab initio quantum-chemical calculations of the energies and structures of 1,2-acetylenedithiol isomers

Ab initio quantum-chemical calculations of 1,2-acetylenedithiol isomers were carried out. The MP2(full), DFT(B3PW91, MPW1PW91), G3, G3B3, and CBS-Q methods were used. According to the calculations, the most stable isomers were 1,2-dithiet, thiiranethione, and trans-1,2-dithioglyoxal. The necessity of including basis set functions with a large angular momentum in calculations was confirmed. The relatively high stability of 1,2-dithiet was attributed to the aromaticity of its four-membered ring. It was noted that the carbon-carbon bond in the three-membered rings of the cis- and trans-isomers of thiirenethiols was unusually short.