Halogen Bonding and Chalcogen Bonding in 4,7-Dibromo-5,6-dinitro-2,1,3-benzothiadiazole

An
organic solid, 4,7-dibromo-5,6-dinitro-2,1,3-benzothiadiazole, has
been designed to serve as an illustrative example to quantitatively
evaluate the relative merits of halogen and chalcogen bonding in terms
of charge density features. The compound displays two polymorphic
modifications, one crystallizing in a non-centrosymmetric space group
(Z′ = 1) and the other in a centrosymmetric
space group with two molecules in the asymmetric unit (Z′ = 2). Topological analysis based on QTAIM clearly brings
out the dominance of the chalcogen bond over the halogen bond along
with an indication that halogen bonds are more directional compared
to chalcogen bonds. The cohesive energies calculated with the absence
of both strong and weak hydrogen bonds as well as stacking interaction
are indicative of the stabilities associated with the polymorphic
forms.