Potential Energy Surfaces of HN(CH)SX:CO₂for X = F, Cl, NC, CN, CCH, and H: N···C Tetrel Bonds and O···S Chalcogen Bonds

Abstract

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 1t J(N–C) for complexes and transition structures and 1 J(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.

Nature of the Interaction of Pyridines with OCS. A Theoretical Investigation

“…The binding energies are refined further from the single point energy calculations at the MP2/aug-cc-pVTZ//MP2/aug-cc-pVDZ level. This method has been applied in several recent studies of noncovalent interaction and found to be quite reliable [46,[56][57][58]. The binding energy of the complexes was calculated using the usual super molecular approach where the energies of the optimized monomers are subtracted from the energy of the complex.…”

Not Only Hydrogen Bonds: Other Noncovalent Interactions

“…Since most molecules have several kinds of atoms, and since all atoms can be Lewis acids, then, confronted with a Lewis base, several types of NCIs can be formed. For this reason, many papers have been devoted to the competition between some combination of hydrogen, alkaline-earth, tetrel, pnictogen, chalcogen, and halogen bonds [157,[183][184][185][186][187][188][189][190]. Curiously, although the nature of the base can change the nature of the most stable acid, none of these publications reported an inversion of acidity.…”

Versatility of the Cyano Group in Intermolecular Interactions

“…Nor is there a limitation to planar geometries, as π-holes are also common in linear molecules, such as the area above the C atom of CO 2 [ 42 , 43 , 44 , 45 , 46 , 47 , 48 ], OCS [ 49 , 50 , 51 ], N 2 O, and CS 2 [ 52 , 53 , 54 ]. Just as their σ-hole analogs facilitate attractions toward a nucleophile, the same is true of these π-holes.…”