Analysis of Oxygen–Pnictogen Bonding with Full Bond Path Topological Analysis of the Electron Density

A variety of methods are available
to investigate the bonding in
inorganic compounds. In contrast to wavefunction-based analyses, topological
analysis of the electron density affords the advantage of analyzing
a physical observable: the electron density. Classical topological
analyses of bonding interactions within the atoms in molecules framework
typically involve location of a bond path between two atoms and evaluation
of a range of real-space functions at the (3, −1) critical
point in the electron density that exists on that bond path. We show
here that counter-intuitive trends are obtained from the analysis
of the electron density (ρ), the Laplacian (∇2ρ), and ellipticity (ε) at the O–E (3, −1)
critical points in the coupled-cluster singles doubles electron densities
of a series of compounds featuring a range of oxygen–pnictogen
bond types: EO+, HEO, H2EOH, H3EOH+, and H3EO (where E = N, P, As, Sb, or Bi). If,
instead, these real-space functions are evaluated along the length
of the bond path, the discrepancies in the trends are resolved. We
show that robust results are also obtained using electron densities
from less computationally demanding density functional theory calculations.
The increased computational efficiency allowed us to also investigate
organic derivatives of these oxygen–pnictogen-bonded compounds
and observe that the trends hold in these instances as well. We anticipate
that these results will be of use to inorganic chemists engaged in
the synthesis and evaluation of novel bonding interactions, particularly
those involving heavy main-group elements.