A theoretical investigation of electronic ground state of parent sulfur diimide

In this paper various properties of parent sulfur diimides (PSD) as the simplest member of sulfur diimides family have been considered using both DFT and ab initio methods employing correlation consistent basis set hierarchies. According to these calculations, EZ conformer is predicted to be the most stable conformer in accord with experimental observation, while its energy difference with ZZ conformer is completely minute. Comparison of microwave gas phase spectra and dense phase IR experimental data with theoretical calculations show a great coincidence. The properties of EE conformer have also been anticipated and its possible presence in dense phase have been discussed although no firm experimental data exists for this conformer. The possible pathways for interconversion between various conformers have been investigated and only two unimolecular type processes namely EZ ↔ EE and EZ ↔ ZZ interconversions have been established according to a pseudo-rotation mechanism as constituting the essential dynamic of system.