Nonpolar Dihydrogen Bonds—On a Gliding Scale from Weak Dihydrogen Interaction to Covalent HH in Symmetric Radical Cations [H_nE‐H‐H‐EH_n]⁺

Abstract

The electronic structures and bonding patterns for a new class of radical cations, [HnE-H-H-EHn]+ (EHn=element hydride, E=element of Groups 15-18), have been investigated by applying quantum-chemical methods. All structures investigated give rise to symmetric potential energy minimum structures. We envisage clear periodic trends. The H--H bond length is shorter for elements toward the bottom of the periodic table of elements, and a short H--H bond corresponds to accumulation of electron density in the central H--H region. All [HnE-H-H-EHn]+ of Groups 15-17 are thermodynamically unstable towards loss of either H2 or H. The barriers for these dissociations are rather low. The Group 18 congeners, except E=Xe, appear to be global minima of the respective potential energy surfaces. The findings are discussed in terms of H2 bond activation, and a general mechanistic scheme for the standard reduction process 2H+ + 2e(-) --> H2 is given. Finally, it is proposed that some of the symmetric radical cations are likely to be observed in mass spectrometric or matrix isolation experiments.

Revealing Factors Influencing the Fluorine‐Centered Non‐Covalent Interactions in Some Fluorine‐Substituted Molecular Complexes: Insights from First‐Principles Studies

“…for the C−F⋅⋅⋅F−C interaction, which was responsible for the integrity of a self‐assembled 2D supramolecular architecture using fully fluorinated compounds . The Δ E values of comparable magnitude have been reported for other non‐covalent interactions …”

Non-Covalent Interactions in Hydrogen Storage Materials LiN(CH3)2BH3 and KN(CH3)2BH3

“…Further Valence Bond studies have revealed [78], in line with our conclusions, that, apart from the crucial dispersion term, also the σ/σ*(C-H) polarization/charge transfer and electrostatic contributions are important. Recently, numerous reports are present in the literature on the stabilizing nature of CH¨¨¨HC interactions in various types of hydrocarbons [37,38,[79][80][81][82][83][84][85], as well as their importance in catalysis [42,43,86].…”

Cationic Complexes of Hydrogen with Helium

“…The calculated dissociation energy of this ion is about 0.21 eV 9. The existence of a long-lived, electronically excited He 2 H 2 + ion with centrosymmetric structure, [He-H-H-He] + , was proposed by Uggerud and co-workers19 and experimentally identified based on its unusual metastable dissociation into HeH + +neutral fragments 20. To the best of our knowledge, no calculations exist for complexes of H 2 + with more than two helium atoms.…”