Dihydrogen bonds and blue‐shifting hydrogen bonds: A theoretical study of AH···HCF3and TH2···HCF3model systems with A = Li or Na and T = Be or Mg

A theoretical study of the molecular properties of AH···HCF3and TH2···HCF3(A = Li or Na and T = Be or Mg) model systems has been carried out at the B3LYP/6‐311++G(3df,3pd) level of theory. Once the interactions between the proton donor (H+δ) of HCF3and protonic hydrides (H−δ) have been produced, these systems appear, at first sight, to be dihydrogen‐bonded complexes. Although a blue‐shift was observed on the HC bond of HCF3upon the formation of the BeH2···HCF3dihydrogen complex, in the case of LiH···HCF3, MgH2···HCF3, and NaH···HCF3, however, a red‐shift was detected on their HCF3species. As far as B3LYP/6‐311++G(3df,3pd) calculations are concerned, we have used the quantum theory of atoms in molecules to evaluate the molecular topography and charge density, according to which higher levels of charge transfer were computed on the red‐shifted complexes. Finally, computation of ΔECdihydrogen bond energies revealed that vibrational red‐shifts are observed in more strongly bonded complexes (values for ΔECranging from 6.67 kJ mol−1to 19.66 kJ mol−1), whereas blue‐shifts are found in weakly bonded ones (higher value for ΔECis 2.31 kJ mol−1).