The electron density delocalization of hydrogen bond systems

Abstract

Recent experimental and theoretical researches have gradually proved that hydrogen bond (H-bond) interactions are not simple traditionally considered electrostatic interaction. Instead, they involve electron density delocalization. In this work, we outline the studies of electronic structures of the H-bond systems in water systems and biological organic molecules systems. Theoretical researches based on the first-principles method have found important evidences for electron density delocalization in H-bond region. Topological analysis based on natural bond orbital (NBO) analysis proves that during the formation of the H-bonds, electrons transfer from B orbitals to A-H antibond orbitals. Energy decomposition analyses revealed that the delocalized electronic structures show strong relations with orbital interactions. Moreover, penetrating molecular orbitals (MOs) are proved to contribute to the electron density delocalization of the H-bonds, and the quantitative contributions for such MOs could be obtained with the electronic density projected integral (EDPI) method. The electronic delocalization and the corresponding penetrating MOs could be visualized in water clusters, based on the firstprinciples method. These researches open a new sight for understanding the electronic structures of H-bonds from atomic level, and even contribute to further controlling proton tunneling as well as charge and energy transfer processes.

Clusterization-triggered emission: Uncommon luminescence from common materials

“…1c shows the crystal structure of ᴅ-hydantoinase [90] . They proposed that the intrinsic fluorescence did not originate from any aromatic residues, and that formation of hydrogen bonds between C=O and N-H groups of these species caused the inter-or intramolecular electron delocalization [91] . Rinaldi et al observed the green emission from poly(ValGlyGlyLeuGly) amyloid-like fibrils in 2007(Fig.…”

“…Additionally, xylitol exhibits RTP. Recently, Wang's group have summarized the electron density delocalization of hydrogenbonded systems [91] . It is generally agreed that the hydrogen bonds involve not only an electrostatic interaction, but they also induce electron density delocalization [155][156][157] .…”

Supersolidity of undercoordinated and hydrating water

“…1) Classical continuum thermodynamics [43][44][45][46][47] embraced the dielectrics, diffusivity, surface stress, viscosity, latent heat, entropy, nucleation, and liquid/vapor phase transition in terms of free energy, though this approach has faced difficulties in dealing with solvation dynamics and the properties of water and ice.…”

“…shows that the -(15− 20) C ice and the 25 C water share the same skin supersolidity -identically shortened and stiffened H-O bond.DFT calculations by Wang and collaborators[47,83] examined the site-resolved electronic binding energy and H−O stretching vibration frequency for medium sized (H2O)n clusters (n = 17-25). They classify the H−O bonds into five groups: the dangling H−O bonds, the H−O bonds associated with the dangling H2O molecules, those with undercoordinated H2O molecules without dangling H−O bonds, those forming the tetrahedral-coordination of the central H2O and the others in its neighbor four molecules.…”

A Covalent‐Like Feature of Intermolecular Hydrogen Bonding in Energetic Molecules 3,6‐Dihydrazino‐s‐tetrazine (DHT)

“…[25][26][27][28][29][30] From the classical perspective, its essence is electrostatic interaction or dipole-dipole forces; [31,32] however, several recent experimental and theoretical studies have presented different views. [33][34][35][36][37][38] The dominating "electrostatic factors" must be strongly antagonistic to H-bond formation, which was demonstrated by studying a class of H-bond complexes between closed-shell ions of similar charge. [34] In addition, the donor-acceptor orbital interactions between electron lone pairs with anti-bond X-H show a number of magnitude contributions to the H-bond strength, which are special properties of the H-bonds.…”