Theoretical analysis of trends in hydrogen bonding involving halogen acceptors (F-At) covalently bonded to a group 14 atom (C-Pb)

摘要

In this work, extensive quantum-chemical calculations have been carried out to identify and elucidate trends in the hydrogen-bonding (HB) interaction involving halogen acceptors covalently bonded to a group 14 atom. A series of 25 heterodimers composed of MH3X (where M = C-Pb and X = F-At) and HNC molecules have been selected as model complexes stabilised by the HB interaction occurring between the X atom of MH3X and the H atom of HNC. The interaction energy (E-int) between MH3X and HNC in the MH3X center dot center dot center dot HNC complexes falls in the range from -2.7 to -10.8 kcal/mol, indicating weak or medium strength of HB in these complexes. The strength of HB in the complexes remains consistent with the well-known HB weakening as X gets heavier. Regarding the effect of M on E-int, the gradual strengthening of HB is observed while descending group 14, but only from M = Si to M = Pb. The trends in E-int are compared with various HB-related parameters obtained from vibrational analysis, the natural bond orbital (NBO) method, the symmetry-adapted perturbation theory (SAPT) and the quantum theory of atoms in molecules (QTAIM). The parameters that present clear (possibly linear) relationships with E-int have been selected to characterise the effect of M and X on the HB interaction.