Comparison of CH···O, SH···O, Chalcogen, and Tetrel Bonds Formed by Neutral and Cationic Sulfur-Containing Compounds

Abstract

The ability of neutral and charged S-compounds to form different sorts of noncovalent bonds is examined by ab initio calculations. Neutrals are represented by CH3SH and fluoro-substituted FSCH3; cations are (CH3)3S(+), CH3SH2(+), and FHSCH3(+). Each is paired with N-methylacetamide (NMA) whose O atom serves as a common electron donor. Charged species engage in much stronger noncovalent bonds than do the neutral molecules, by as much as an order of magnitude. The strongest noncovalent bond for any system is a O···SF chalcogen bond wherein the O lies directly opposite a S-F covalent bond, amounting to as much as 39 kcal/mol. Second in binding energy is the SH···O H-bond, which can be as large as 34 kcal/mol. Somewhat weaker is the O···SC chalcogen bond, followed by the CH···O H-bond and finally the O···C tetrel bond, which has the appearance of a trifurcated H-bond. Any CH group that participates in a CH···O H-bond shifts its NMR signal downfield by an amount roughly proportional to the strength of the H-bond. This situation is clearly distinguishable from that in a O···S chalcogen or SH···O H-bond wherein the methyl protons are shifted upfield.

Tuning the Competition between Hydrogen and Tetrel Bonds by a Magnesium Bond

“…[58][59][60][61][62][63] To ensure the structures obtained were minima on the potential energy surface, frequency calculations were also performed at the same level, affirming all structures have no imaginary frequencies. [58][59][60][61][62][63] To ensure the structures obtained were minima on the potential energy surface, frequency calculations were also performed at the same level, affirming all structures have no imaginary frequencies.…”

Hexacoordinated Tetrel‐Bonded Complexes between TF4 (T=Si, Ge, Sn, Pb) and NCH: Competition between σ‐ and π‐Holes

“…Despite any barriers to their formation, these tetrel bonds occur widely and are of great import in a number of chemical and biological processes. [35][36][37][38][39][40][41][42] The scale and effects of the geometric deformation of the TR 4 molecule required to accommodate a Lewis base have been assessed quantitatively. [9,10] Scores of tetrel bonds have been identified within protein structures, [11][12][13][14][15] and are implicated in the catalytic process of several enzymes.…”

Supramolecular Covalence in Bifurcated Chalcogen Bonding

“…Evidence for thed irectionality of YBs comes from variouss tudies of intermolecular interactions involving sulfur. [56,61] S···O, S···N, and S···S YBs involving methionine andc ysteine have been identified in proteins,a nd it has been suggested that they mayp romote protein folding and stability. [49,[52][53][54][55][56][57][58][59][60] Theoretical calculations have suggestedt hat the strength of the YB between neutral systemsi sc omparable to that of aw eak HB, [39] whereas some interactions involving ac halcogen cation can have very high interaction energies.…”