Dihydrogen contacts in alkanes are subtle but not faint

Abstract

Alkane molecules are held together in the crystal state by purportedly weak homonuclear R-H···H-R dihydrogen interactions. In an apparent contradiction, the high melting points and vaporization enthalpies of polyhedranes in condensed phases require quite strong intermolecular interactions. Two questions arise: 'How strong can a weak C-H···H-C bond be?' and 'How do the size and topology of the carbon skeleton affect these bonding interactions?' A systematic computational study of intermolecular interactions in dimers of n-alkanes and polyhedranes, such as tetrahedrane, cubane, octahedrane or dodecahedrane, showed that attractive C-H···H-C interactions are stronger than usually thought. We identified factors that account for the strength of these interactions, including the tertiary nature of the carbon atoms and their low pyramidality. An alkane with a bowl shape was designed in the search for stronger dihydrogen intermolecular bonding, and a dissociation energy as high as 12 kJ mol⁻¹ is predicted by our calculations.

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

“…It is important to reference other works where dispersion dominated CH¨¨¨HC interactions have been found-Echeverría and coworkers found, based on MP2 studies, the "subtle but not faint" stabilizing CH¨¨¨HC interactions between alkanes [77]. 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.…”

Physical Nature of Interactions in ZnIIComplexes with 2,2′-Bipyridyl: Quantum Theory of Atoms in Molecules (QTAIM), Interacting Quantum Atoms (IQA), Noncovalent Interactions (NCI), and Extended Transition State Coupled with Natural Orbitals for Chemical Valence (ETS-NOCV) Comparative Studies

“…Echeverría et al 34 [66][67][68][69] and (4) (ETS-NOCV) energy decomposition scheme. [70][71] It is, to the best of our knowledge, not only the first comprehensive work combining all four methods, but it also characterizes all the intra-and intermolecular interactions in the Zn II -complexes with bpy.…”

“…It is important to note that Bader and co-workers interpreted close contacts CH--HC in some molecules as the bonding interactions, either from the calculated [29][30][31][32][33][34][35][36][37] or experimental 29,[38][39][40] electron density distributions, using the quantum theory of atoms in molecules (QTAIM). 41 The formation of H-H bonding interactions in simple molecules (like biphenyl, phenanthrene) was then challenged in the literature [42][43][44][45][46] and rebutted.…”

Di-hydrogen contact induced lattice instabilities and structural dynamics in complex hydride perovskites

“…Beyond that, the lattice dynamics are enhanced by molecular B-H vibrations and tumbling motions (reorientations) of the molecule, which occur at relatively higher and lower energies with respect to lattice phonons. Finally, the above introduced di-hydrogen contacts, though spanning low interaction energies between approximately 2 and 120 kJ − mol 1 [8], make up a large number of interactions per unit cell in complex hydride condensed solids, and are thus expected to participate in dominating structural behaviour, presumably interacting with lattice dynamics. The main objective of this article is to provide insight into the structural details and lattice dynamics on various time-scales governing the interesting nature of polymorphic transformations in borohydride perovskites.…”