Hydrogen bonds determine the structures of the ternary heterocyclic complexes C2H4O···2HF, C2H5N···2HF and C2H4S···2HF: density functional theory and topological calculations

Abstract

A theoretical study of structural, electronic, topological and vibrational parameters of the ternary hydrogen-bonded complexes C(2)H(4)O···2HF, C(2)H(5)N···2HF and C(2)H(4)S···2HF is presented here. Different from binary systems with a single proton donor, the tricomplexes have the property of forming multiple hydrogen bonds, which are analyzed from a structural and vibrational point of view, but verified only by means of the quantum theory of atoms in molecules (QTAIM). As traditionally done in the hydrogen bond theory, the charge transfer between proton donors and acceptors was computed using the CHELPG calculations, which also revealed agreement with dipole moment variation and a cooperative effect on the tricomplexes. Furthermore, redshift events on proton donor bonds were satisfactorily identified, although, in this case, an absence of experimental data led to the use of a theoretical argument to interpret these spectroscopic shifts. It was therefore the use of the QTAIM parameters that enabled all intermolecular vibrational modes to be validated. The most stable tricomplex in terms of energy was identified via the strength of the hydrogen bonds, which were modeled as directional and bifurcated.

Structure, energy, vibrational spectrum, and Bader's analysis of π⋯H hydrogen bonds and H−δ⋯H+δdihydrogen bonds

“…The spectroscopy techniques and DFT calculations have been used conjointly for investigating the vibrational modes of bifurcate dihydrogen bonds, 637 as reported in the pioneering study conducted by Nikonov et al 638 The values for the main stretching frequencies and absorption intensities of the bifurcate dihydrogen complexes BeH 2 Á Á Á2(HCN) (23) and BeH 2 Á Á Á2(HNC) (24), and linear ones HCNÁ Á ÁBeH 2 Á Á ÁHCN (25) and CNHÁ Á ÁBeH 2 Á Á ÁHNC (26) are listed in Table 7. In agreement with other studies, 639 it can be seen that the stretch frequencies of the bonds (H +d -C) -A and (H +d -C) -B are displaced downward in value. However, the H +d -N bonds of 24 (bifurcate) and 26 (linear) provide the largest red-shifts, with values of À37.4 and À75.3 cm À1 respectively.…”

“…In a contrasting reflection on this but already discussed here, it is well-known that ternary hydrogen complexes formed by p or lone-electron pairs as proton acceptors are much more stable than binary complexes in terms of their intermolecular distances. 213,378,397,398,639,645,646 Unfortunately, this observation is not verified here, but it is common because increases in double or bifurcate dihydrogen bond distances are well-known, 555,556,647 e.g., dihydrogen-bonded systems formed by ethyl cation and beryllium hydride. 398 Nevertheless, it can be seen that the values of 2.1404 Å (32) and 1.7934 Å (33) for H Àd Á Á ÁH +d are shorter than the sum of the van der Waals radii for the hydrogen atom, whose tabulated datum is 1.09 Å.…”

Quantum chemical studies of non-covalent interactions between the ethyl cation and rare gases

“…1 In conformity with these assertions, but in view of the applicability in investigations of chemical bonds and interatomic distances [63,64], the interaction distance at the B3LYP/6-311 + +G(d,p) of I is shorter than the values reported by Goswani and Arunan [65] regarding the H 2 OÁÁÁ2Ar and H 2 SÁÁÁ2Ar complexes at the MP2(full)/aug-cc-pVTZ level of theory. Absolutely, this is not enough to discriminate the efficiency between these levels of theory, but otherwise it also serves to show that ternary structures have not necessarily shorter intermolecular distances and higher interaction energies compared with binary ones [21,27,66,67]. In addition to HÁÁÁRG, the values of the bond lengths of both CÁÁÁH and p are also depicted in Fig.…”

“…Besides dihydrogen bonds [6][7][8][9][10], halogen bonds [11][12][13][14], dihydride-halogen bonds [15][16][17], beryllium bonds [18], and pnicogen bonds [19,20], in general the electron flux on these interactions occur from high-electron-density centers, such as proton acceptors, towards the electrondepleted ones, which are represented by hydrogen donors [21][22][23][24]. Clearly, this electronic gearing controls the formation of these non-covalent links [25][26][27]. Anyhow, the research of new forms of intermolecular contacts is focused on the analysis of the high electron-density entity, because it is from the hyperconjugative interaction (charge transfer) [28] between the frontier molecular orbitals occurs.…”

Theoretical aspects of binary and ternary complexes of aziridine⋯ammonia ruled by hydrogen bond strength

“…It is worth remembering that, by definition, the classical model of the hydrogen bond takes into consideration one stable interaction between a center with high electronic density and a proton donor, such as a loneelectron pair or unsaturated bond and a Lewis acid [20][21][22][23], respectively. From a theoretical standpoint, among the large number of computational studies published in recent years [24], we would like to emphasize one specific work that paid great attention to the occurrence of hydrogen bonds in the binary systems formed by thiirane and ammonia [25].…”