A B3LYP and QTAIM study of a new proton donor for dihydrogen bonds: the case of the C2H5 +•••nBeH2 complexes (n=1 or 2)

B3LYP/6-311++G(d,p) calculations and molecular integrations from the quantum theory of atoms in molecules (QTAIM) were performed for the purposes of studying a new class of dihydrogen-bonded hyperconjugation complexes formed by C2H5 (+)center dot center dot center dot n(BeH2), when n = 1 (bimolecular) or n = 2 (trimolecular). Whether bimolecular or trimolecular, when the hyperconjugation on the ethyl cation (C2H5 (+)) is taken into account, this enables the earth alkaline hydride, BeH2, to interact efficiently with the nonlocalized hydrogen (H+) of the C2H (5) (+) . In addition to computation of QTAIM topological parameters, analysis of the infrared harmonic spectrum at the B3LYP/6-311++G(d,p) level of theory revealed the existence of red-shifts on BeH2, and this effect is explained by means of the atomic charges derived from the ChelpG approach.