Isotope effects in linear dihydrogen bonded complexes containing LiH

Abstract

An ab initio study of linear dihydrogen-bonded complexes containing LiH (acting as a proton acceptor) was undertaken. The complexes studied were LiH⋯HF, LiH⋯HCN, and LiH⋯HCCH. Equilibrium geometries and harmonic vibrational frequencies were computed at various levels of theory using a 6-31++G(d,p) basis set. It was found that the LiH⋯HF complex was not stable at all levels of theory. The relative stabilities of H-bonded and D-bonded isotopomers of LiH⋯HCN and LiH⋯HCCH were determined by differences in zero-point vibrational frequencies. For LiH⋯HCN isotopomers, it was found that the LiD⋯HCN was favored over LiH⋯DCN with a relative stability of 54 cm−1 calculated at the Quadratic Configuration Interaction—Singles and Doubles level. Similarly, LiD⋯HCCH is favored over LiH⋯DCCH, with a lower value for the relative stability. The relative stabilities of the H-bonded and D-bonded species LiH⋯HCCD and LiH⋯DCCH indicated that the D-bonded complex was energetically favored, in accordance with the Buckingham–Liu theory.

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

“…[33] This result supports the conclusion that the strength of dihydrogen bond has a positive relation to the acidity of hydrogen proton in the proton donor. [31] The DE corr of the dihydrogen bond of trimer I increases by about 26 % relative to that of dimer I.…”

“…The initial structures of the LiH-HCN-HCN and LiH-HCN-HCN-HCN complexes ( Figure 1) were based those obtain in previous studies of LiH-HCN [29,33] and HCN-HCN. [15,16] The geometries of the complexes and their monomers were initially optimized at the MP2/6-311 + + GA C H T U N G T R E N N U N G (2d,2p) level.…”

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

“…It is found that there is no fundamental difference between the properties and nature of dihydrogen bonds and those of conventional hydrogen bonds. For example, the strength of dihydrogen bond has a positive relation with the proton acidity of the proton donors as does conventional hydrogen bond [9,28]. However, no study on the effect of methyl group on the properties of dihydrogen bonds has been reported.…”

“…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).…”

MH⋅sHX Dihydrogen Bond with M≡Li, Na and X≡F, Cl, Br: A CP-Corrected PES Calculation and an AIM Analysis

“…Series of gas phase studies of dihydrogen-bonded systems can be found in literature (see for example [6][7][8][9][10][11][12][13][14][15][16][17] as the most recent studies). One of the MH molecules mostly used is LiH, where the hydrogen atom has clear hydride behaviour, holding a charge about −0.8 au.…”