Origin of cooperativity in hydrogen bonding

Abstract

The origin of non-additivity in hydrogen bonds (H-bonds), usually termed as H-bond cooperativity, is investigated in H-bonded linear chains. It is shown that H-bond cooperativity originates solely from classical electrostatics. The latter is corroborated by comparing the H-bond cooperativity in infinitely-long H-bonded hydrogen cyanide, 4-pyridone and formamide chains, assessed using density functional theory (DFT), against the strengthening of the dipole-dipole interaction upon the formation of an infinite chain of effective point-dipoles. It is found that the magnitude of these effective point-dipoles is a consequence of mutual polarization and additional effects beyond a polarizable point-dipole model. Nevertheless, the effective point-dipoles are fully determined once a single H-bond is formed, indicating that quantum effects involved in H-bonding are circumscribed to nearest-neighbor interactions only; i.e. in a linear chain of H-bonds, quantum effects do not contribute to the H-bond non-additivity. This finding is verified by estimating cooperativity along the dissociation path of H-bonds in the infinite chains, using two empirical parameters that account for polarizability, together with DFT association energies and molecular dipoles of solely monomers and dimers.

Cooperativity in alkane‐1,2‐ and 1,3‐polyols: NMR, QTAIM, and IQA study of O─H…OH and C─H…OH bonding interactions

“…A great deal of work on the quantification of hydrogen bond cooperativity has been devoted to intermolecular interactions within chains and clusters of small amide molecules, 8–12 formaldehyde, 13, 14, 17 alcohols, 16, 17 water, 3, 17, 18 hydrogen cyanide, 12, 15 and so forth, as well as many combinations of small molecules 3 . In monomer chains, the average hydrogen bond energy or any other parameter that can be associated with cooperativity varies much more for a very short chain extension, such as going from a dimer to a trimer, than for further elongation 13, 14 .…”

“…In the context of hydrogen bonding, this implies that bond strengths should be mutually enhanced, that is, that the strengths of two interacting bonds should be higher than those of the isolated bonds 6 . Cooperativity in long chains or clusters of small monomers or mixtures of different monomers has been widely studied by theoretical methods, 3,7–18 but work on intramolecular cooperativity going beyond two or three interacting bonds is much more limited 19–23 . It is generally assumed that in carbohydrates, where there are chains or clusters of OH groups, many features, for example, stability, molecular recognition, and binding with acceptors, are determined by long‐range cooperative effects 24–27 .…”

The σ and π Holes. The Halogen and Tetrel Bondings: Their Nature, Importance and Chemical, Biological and Medicinal Implications

“…Thus, it is worth noting that hydrogen bonds become substantially stronger when forming a network ,. The origin of this hydrogen bonds cooperativity is primarily electrostatic as its magnitude can be determined by a pairwise addition of effective point dipoles . As will be discussed below, the forces and interactions producing cooperativity in tetrels and halogens bonding may be in some way more complicated.…”

Charting Hydrogen Bond Anisotropy

“…Molecules in the condensed phase tend to be more polarized than in the gas phase 43 because of the eletrostatic stabilization provided by the adjacent molecules. This cooperative effect plays an important role for HB networks where molecules act as donors and acceptors simultaneously 44 .…”

“…The polarization induced by the water molecule 44 affects strengths of both probe-target and target-water interactions. The result is a strength increase for all six sites considered, with ∆E wat approximately 3% to 25% larger than the corresponding ∆E opt of dimers without the added waters ( Supplementary Tables S3 and S4).…”