The bifurcate chalcogen bond: Some theoretical observations

The bifurcate S(SS)⋯Y (Y = F−, Cl−, Br−, N or O) interactions have been investigated theoretically at the MP2/aug-cc-pVDZ theory level. The strength of the strongest bifurcate chalcogen bond studied was found to be about 35 kcal/mol, larger than that of any known halogen bond. Employing the natural bond orbital analysis, the nature of the bond-length change and the corresponding spectral shift upon bifurcate chalcogen bond formation was also studied.