Chapter 16: Structural Features of Chalcogen Bonds and Weak Interactions Involving Chalcogens

The structural features of chalcogen bonding (ChB) interactions in linear fragments R–Ch⋯Nu (Ch = S, Se, Te; R = C, N, O, S, Se, Te; Nu = N, O, S, Se, Te, F, Cl, Br, I) involving Ch⋯Nu distances shorter than the sum of relevant van der Waals (vdW) radii are reviewed. For the R–Ch⋯Nu fragments, the structural parameters d_R–Ch and d_Ch⋯Nu are analyzed along with the values of the functions δ_R–Ch and δ_Ch⋯Nu calculated by normalizing the differences between the involved covalent R–Ch and non-covalent Ch⋯Nu distances and the sum of the relevant covalent and van der Waals (vdW) radii, in order to compare the data involving different Ch atoms. A systematic comparison of the ChB found in isologue fragments R–Ch⋯Nu is presented sorted by the nature of the involved Ch atom, of the R atoms covalently bonded to the Ch, and of the Nu species playing the role of chalcogen bond acceptors.