Properties of the C−H···H Dihydrogen Bond:  An ab Initio and Topological Analysis

Abstract

The dihydrogen-bonded complexes of methane and its fluoro and chloro derivatives with lithium hydride are analyzed using ab initio methods as well as the Bader theory. All calculations were performed using Pople's basis sets (6-311++G(d,p), 6-311++G(2df,2pd), and 6-311++G(3df,3pd)) and the Dunning bases (aug-cc-pVDZ and aug-cc-pVTZ) within the MP2 method. The results of the calculations show that the binding energy for the analyzed complexes increases with the increase of the number of fluoro or chloro substituents, up to ∼7 kcal/mol. In the same order there is an increase of the electrostatic energy term, showing that for the CF3H···HLi complex the dihydrogen bond interaction is similar in nature as for the water dimer where a conventional O−H···O hydrogen bond exists, while for the CCl3H···HLi dimer the exchange energy term outweighs the electrostatic energy. Hence, the other attractive energy terms are important. A topological analysis based on the Bader theory supports the results of the ab initio calculations since the electron densities at the H···H bond critical points and the other topological parameters are similar to those calculated for moderate conventional hydrogen bonds.

Regulating function of methyl group on the strength of dihydrogen bond in HBeH-HCCH and HMgH-HCCH complexes

“…The dihydrogen bond is enhanced when the reactivity of metal hydrides is increased [3,4]. The usual proton donors in dihydrogen bonds are FH, OH, and NH groups [5][6][7], like those in conventional hydrogen bonds, although the dihydrogen bonds with CH and SH groups acting as a proton donor have also been reported [8][9][10][11][12]. The binding distances between the two interacting hydrogen atoms are typically 1.7-2.2 Å [13], significantly less than the sum of the van der Waals radii for the two hydrogen atoms (2.4 Å).…”

Cooperativity between the Dihydrogen Bond and the N⋅⋅⋅HC Hydrogen Bond in LiH–(HCN)nComplexes

“…The properties and nature of conventional and unconventional hydrogen bonds have been compared and unveiled. [11][12][13][14] There also has been some investigation into the cooperativity of unconventional hydrogen bonds. The cooperativity of the CH···O hydrogen bond in (H 2 CO) n and (HFCO) n clusters was compared to that of the OH···O hydrogen bond in (H 2 O) n clusters.…”

“…[28] The dihydrogen bond is an important unconventional hydrogen bond, in which the proton acceptor is often a metal hydride. [10] In recent years, many studies on the properties and structures of dihydrogen bonds have been performed, [13,14,[29][30][31] but, to the best of our knowledge, there is no study on the cooperativity of dihydrogen bonds. There are a few studies on its cooperativity with other types of hydrogen bonds.…”

Theoretical Study on Structures and Properties of N2O···HOCl Complexes

“…As for halogen bond interaction in complex S4, its ▽ 2 ρ(r) and ρ(r) are similar to those of S1. In addition, Lipkowski 47 pointed out that the electron density and positive values of the Laplacian quantity in hydrogen bond system should be in the range of 0.002-0.04 and 0.02-0.15 a.u. Here, in the hydrogen bond complexes S2, S3, S5 and S6, ρ(r) and ▽ 2 ρ(r) all lie in the range of what Lipkowski suggested.…”