Directionality of Hydrogen Bonds to Sulfur and Oxygen

Abstract

Hydrogen-bonded complexes involving sulfur bases are found to be quite different from the analogous oxygen complexes, both experimentally and in theoretical calculations. In general, hydrogen bonds to sulfur not only are weaker than those to oxygen but also show a marked preference for a more “perpendicular” direction of approach to the donor atom. Ab initio calculations at the MP2/6-311++G(d,p) level on the complexes of hydrogen fluoride with H2O, H2S, H2CO, and H2CS reproduce these differences, as does a search of structures in the Cambridge Crystallographic Data Base. We show that the Laplacian of the charge density ∇2ρ predicts a qualitatively correct structure for all the systems considered, but gives poor quantitative predictions of hydrogen-bonding geometries. An analysis based upon Bader's atoms-in-molecules theory rationalizes the differences between sulfur and oxygen hydrogen bonds. A treatment of the hydrogen bond which explicitly considers the contributions of atomic multipoles to the electrostatic energy has more success than ∇2ρ in predicting H bond directionality. Hydrogen bond formation to oxygen is driven by charge−charge interactions, whereas with sulfur the stabilization arises principally from the interaction of the charge on the acidic hydrogen with the dipole and quadrupoles of sulfur.

Hydrogen Bonding in Phosphine Oxide/Phosphate–Phenol Complexes

“…As could be expected on the basis of van der Waals radii and relative electronegativities, [42] the shortest H-bond lengths are found for the strongest complexes. The H-bond length in complexes with phenol (OH···O/S) is roughly 0.3 shorter than with thiophenol (SH···O/S), which we attribute to the lower tendency of thiophenol to form H-bonds.…”

“…The shallow energy well for sulfur-containing compounds can also be observed from another geometric parameter. Previous investigations [33,42] suggest that whereas H-bonds to oxygen (O=) are typically linear, sterically unconstrained Hbonds to sulfur atoms (S=) are linear in some cases [47] while they are strictly nonlinear in others (e.g., a = 151-1588). [33] In the current cases the H-bond angle a !…”

“…[33,42] The increase in H-bond length (Dd H···O/S ) found here for sulfides compared to oxides is somewhat higher than previously reported for a similar substitution: an increase in H-bond length of~0.5 was found for HF-thioether and HF-thiocarbonyl complexes with respect to the analogous H-bonds to oxygen, [42] whereas we find an increase of 0.66 for a H-bond to S=P with respect to a H-bond to O=P. This is most likely largely due to the fact that HF is a stronger acid than (thio)phenol, and is thus more prone to partial proton transfer, which would increase the H-bond length to a lesser extent, as indeed seen here.…”

Ab initio and DFT investigations of lithium/hydrogen bonded complexes of trimethylamine, dimethyl ether and dimethyl sulfide

“…Generally, the amine and ether prefer linear lithium/hydrogen bonds, while sulfur prefers perpendicular lithium/hydrogen bonds in line with the previous studies. 45 Slight deviation from linearity in the complex arises from an LiFÉ É ÉO(CH 3 ) 2 electrostatic interaction of Ñuorine with methyl protons. NBO analysis reveals that the amine and ether donate their lone n s pair and sulÐde donates its lone pair.…”

Low-temperature adsorption of H2S on Ag(111)

“…[12][13][14][15][16][17] The importance of hydrogen bonding in the structures of H 2 O aggregates on Ag͑111͒ has been confirmed by detailed scanning tunneling microscopy ͑STM͒ and DFT studies of Morgenstern, Michaelides et al [15][16][17][18][19][20][21][22][23][24][25][26] Like H 2 O, H 2 S forms H bonds in the gas, liquid, and solid states. However, its H bond is only about half as strong as that of H 2 O, 27 and its internal molecular geometry is considerably different: The S-H bond is longer than the O-H bond ͑0.133 nm vs. 0.095 nm͒, and its internal bond angle is smaller ͑92.2°versus 104.5°͒. Given these differences, it is unclear a priori whether H 2 S will form hydrogen-bonded clusters on Ag͑111͒, and if so, what their geometry will be.…”