Impact of deformation energy on the hydrogen bonding interactions in gas phase 3-X catechol⋯H2O complexes (X = H, F, Cl, Br): The effect of approach of a water molecule

Strengthening of Noncovalent Bonds Caused by Internal Deformations

“…It is important to recognize that there are numerous cases in the literature where internal deformations are an important component in the interaction between molecules. , Many of these issues arose in the study of H-bonds, − but have broadened to numerous other sorts of interactions. Some examples include the formation of complexes between FCu and unsaturated hydrocarbons, which presented the difficulty of pushing the two monomers together without allowing the necessary internal geometry changes.…”

“…The primary means of distortion that can drive such a process involves the reduction of the internal angles within the acid, pulling the substituents closer toward one another. In addition to reducing steric repulsion, the internal modification can also yield changes in hybridization or improved matching of orbital energies, which can also enhance the interaction. ,,,, Simply pushing the two molecules in toward one another and then allowing the units to make internal geometric adjustments to this contraction leads to much smaller intermolecular bond strengthening. Likewise, only a small effect is observed from the adjustment of the internal bond lengths within the Lewis acid.…”