J. Phys. Chem. A 123, 7270-7277 (2019)

DOI: 10.1021/acs.jpca.9b04144

Potential Energy Surfaces of HN(CH)SX:CO2 for X = F, Cl, NC, CN, CCH, and H: N···C Tetrel Bonds and O···S Chalcogen Bonds

MP2/aug′-cc-pVTZ calculations have been performed in search of complexes, molecules, and transition structures on the HN(CH)SX:CO2 potential energy surfaces, for X = F, Cl, NC, CN, CCH, and H. Complexes stabilized by traditional N···C tetrel bonds and O···S chalcogen bonds exist on all surfaces and are bound relative to the isolated monomers. Molecules stabilized by an N–C covalent bond and an O···S chalcogen bond are found when X = F, Cl, and NC, but only the HN(CH)SF:CO2 molecule is bound. The binding energies of these complexes correlate with the O–S distance but not with the N–C distance. Binding energies of complexes rotated by 90° about the N···C tetrel bond and by 90° about the O···S chalcogen bond provide estimates of these bond energies. Charge-transfer energies across tetrel and chalcogen bonds correlate with the N–C and O–S distances, respectively. As a function of the N–C distance, equation-of-motion coupled cluster singles and doubles spin–spin coupling constants 1tJ(N–C) for complexes and transition structures and 1J(N–C) for molecules describe the evolution of the N···C tetrel bonds in the complexes and transition structures to N–C covalent bonds in the molecules. The O···S chalcogen bond gains some covalency in the transition structures and again in the molecules but does not become a covalent bond.