DFT based engineering of N-heterocyclic carbenes to exacerbate its activity for SO2 fixation and storage.

Carbene compounds are very reactive to SO2 which assert their candidature to seize this greenhouse gas. Unfortunately, most of the carbenes which produce S,S-dioxide with SO2, undergo dissociation to yield ketone derivative and SO through an intermediate formation of oxathiirane S-oxide derivative. Thus, carbenes are excluded from the list of catalyst for SO2 fixation and storage technology. To eradicate this retardation, the stability of different oxathiirane S-oxide derivatives obtained from SO2 and 56 carbenes of various structures are studied using Density Functional Theory (DFT). Through our study, we are able to find out three oxathiirane S-oxide derivatives which have positive ΔG values for their decomposition to the respective ketone derivatives. This study corroborates that proper engineering of carbene leads to produce a stable oxathiirane S-oxide derivative as a stable product. We observed that carbenes are highly efficient to nab SO2 at room temperature. This finding should necessitate the recommencement of the use of carbene for SO2 fixation technology. We also found three carbenes which are able to produce sulfene derivative (C - S bond length is less than 1.7 Å) on reaction with SO2.