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Cover Picture: Hydrogen–Hydrogen Bonding: A Stabilizing Interaction in Molecules and Crystals (Chem. Eur. J. 9/2003)
Author(s) -
Matta Chérif F.,
HernándezTrujillo Jesús,
Tang TingHua,
Bader Richard F. W.
Publication year - 2003
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Reports
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200390217
Subject(s) - van der waals force , hydrogen bond , chemistry , crystallography , molecule , van der waals strain , van der waals radius , atoms in molecules , hydrogen , hydrogen atom , steric effects , chemical physics , computational chemistry , stereochemistry , organic chemistry , group (periodic table)
The cover picture shows a schematic representation of the change in structure accompanying the planarization of biphenyl through the formation of bond paths between the pairs of ortho ‐hydrogen atoms. The top figure for the twisted equilibrium structure portrays four of the rings of hydrogen atoms, each shown as a spatial region defined by the intersection of its C|H interatomic surface with the van der Waals surface defined by the 0.001 au electron density envelope, the surfaces for the pairs of ortho ‐hydrogen atoms touching at the geometry of the equilibrium structure. Planarization results in a lengthening of the CC separation between the rings by ∼0.01 Å, and the ortho ‐hydrogen atoms are brought to separations ∼0.04 Å less than twice their van der Waals radii. The resulting increase in the energy of the carbon atoms is, however, largely negated by HH bonding, that is, the formation of an interatomic surface and an associated bond path linking each pair of ortho ‐hydrogen atoms. Thus the ortho ‐hydrogen atoms in planar biphenyl do not experience “steric nonbonded repulsions”, but rather, like all interactions denoted by a bond path, make a stabilizing contribution to the energy of ∼10 kcal mol −1 per HH interaction. HH bonding is present between the corresponding hydrogen atoms in polybenzenoids, such as phenanthrene and chrysene, and it is the presence of such interactions between the hydrogens of methyl groups in neighboring tetra‐ tert ‐butyl groups that encapsulate and stabilize the otherwise unstable tetrahedrane and cyclobutadiene molecules. For further details see the article by R. F. W. Bader et al. on p. 1940 ff.