Inter- and Intramolecular Interactions in Crystalline 2‑Nitrobenzoic AcidAn Experimental and Theoretical QTAIM Analysis

We have quantified the inter- and
intramolecular interactions in crystalline 2-nitrobenzoic acid from
QTAIM analysis of the topology of the electron density distribution
obtained from both a low temperature (20 K) X-ray diffraction experiment
and from theoretical calculations. The covalent bonds have been characterized
by the properties at their (3,–1) bond critical points; in
particular the nature of the aromatic/nitro group C–N bond
is discussed. All noncovalent bonds of the type O···H
(both strong and weak), C···C, O···O,
and O···C have also been characterized. Intermolecular
interactions may be roughly divided into three types, the formation
of a classical carboxylic acid hydrogen bonded dimer, an unusual ribbon
of O···O interactions parallel to a, and a number of predominantly O···H interactions
perpendicular to a. Integrated atomic charges (in
particular for the acidic hydrogen, ∼+0.6) and the derived
molecular dipole moment are reported.