Intramolecular CS⋯OS(C) chalcogen bonds: A theoretical study of the effects of substituents and intermolecular hydrogen bonds

Abstract According to our search of the Cambridge Structural Database, a huge number of crystal structures involving intramolecular C S⋯O S(C) interactions were extracted. The largest proportion of these interactions in the crystals shows rather good linearity and short interatomic S⋯O distances. Then, intramolecular C S⋯O S(C) interactions in three representative organic molecules, i.e. sulfamethizole, thioindirubin, and thiazolo-pyridinium methide, were investigated using density functional theory calculations at the M06-2x level. The effects of different substituents and intermolecular hydrogen bonds on these interactions were also examined. The presence of both electron-withdrawing and electron-donating substituents into the donor moiety tends to strengthen intramolecular S⋯O bonds, while the formation of intermolecular hydrogen bonds has a complex influence. To gain a deeper understanding of the nature and strength of these interactions, the analyses of atom in molecules, noncovalent interaction index, and natural bond orbital were undertaken. Intramolecular chalogen bonds are weak electrostatic interactions and play a key role in controlling the crystal forms of relevant organic compounds, frequently supported by intermolecular hydrogen bonds.