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Complexes of O=C=S with Nitrogen Bases: Chalcogen Bonds, Tetrel Bonds, and Other Secondary Interactions
Author(s) -
Alkorta Ibon,
Elguero José,
Del Bene Janet E.
Publication year - 2018
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201800217
Subject(s) - chalcogen , hydrogen bond , chemistry , crystallography , imidazole , coupling constant , computational chemistry , stereochemistry , molecule , organic chemistry , physics , particle physics
Ab initio MP2/aug’‐cc‐pVTZ calculations have been carried out to investigate chalcogen‐bond formation through the σ‐hole at S and tetrel‐bond formation through the π‐hole at C in complexes of OCS with a series of nitrogen bases. The binding energies of chalcogen‐ and tetrel‐bonded complexes with the sp‐hybridized bases correlate exponentially with the N−S and N−C distances, respectively. The presence of secondary interactions between an N−H or C−H group of an sp 2 ‐hybridized base and OCS in chalcogen‐bonded complexes decreases the correlation between binding energies and the N−S distance. These secondary interactions are stronger in the tetrel‐bonded complexes with the sp 2 bases, particularly in the isomers of OCS:imidazole and OCS : N 2 H 2 , where they may be described as distorted N−H⋅⋅⋅O or N−H⋅⋅⋅S hydrogen bonds. Charge‐transfer interactions are consistent with the nature of the primary and secondary interactions in these complexes. The in‐plane OCS bending frequencies are blue‐shift in the chalcogen‐bonded complexes, and red‐shifted in the tetrel‐bonded complexes. EOM‐CCSD spin‐spin coupling constants 1c J(N4−S) across chalcogen bonds have absolute values less than 9.0 Hz, while the two‐bond coupling constants 2c J(N4−C) do not exceed 4.0 Hz. These are greater in absolute value that the one‐bond coupling constants 1t J(N4−C) across tetrel bonds that are less than 0.5 Hz at much shorter N−C distances.