The interaction strength of intermolecular systems formed by NaH⋯2(HF) and NaH⋯4(HF): Hydrogen bonds, dihydrogen bonds and halogen–hydride bonds

Abstract

In this paper, a theoretical study of the molecular properties of NaH/2(HF) and NaH/4(HF) complexes is reported. Based on MP2/6-311þþG(d,p) calculations, the dihydrogen bonds (H/H), hydrogen bonds (F/H) and halogen-hydride bonds (F/Na) of these intermolecular systems were fully characterized. The characterization involved the following procedures: the examination of structural parameters, analysis of vibration modes such as frequencies shifted to red or blue in the infrared spectrum, modeling of the electronic topology, quantification of the cooperative energy followed by charge transfer and, finally, natural bond orbital analysis. The results show short intermolecular distances with high electronic density, while the stretch frequencies of the proton donors and acceptors are unusually shifted, and some values reach 1000 cm À1 . When all subunits of the complexes are taken into account, in this case the NaH and HF molecules, the high value for the strength of the H/H dihydrogen bond in NaH/2(HF) suggests the formation of an additional subpart, i.e., the H 2 molecule.

Cooperation of Peripheral Hydrogen Atoms for the Stabilization of Aachno-pentaborane (11) with Small Molecules: Hydrogen Bonds and Dihydrogen Bonds

“…Values of ρ and ∇ 2 ρ are given in e.ao -3 and e.ao -5 , respectively; Values of G and V are given in electronic unites (e.u.). Nevertheless, the qualitative prediction of the interaction strength can be stressed through the contributions of both descriptors G and V, especially through the ratio between them [56]. The -G/V ratio classifies the interaction strength as i) noncovalent if -G/V > 1; ii) partially covalent if 0.5 < -G/V < 1.0; and iii) totally covalent if -G/V < 0.5 [57].…”