To do this requires utilization and understanding of a wide
range of supramolecular interactions including classical hydrogen
bonds [3,4], weak hydrogen bonds (e.g. CAH N/O interactions)
[5,6] and p–p interactions [8,9]. A more recent addition to the
aforementioned interactions is halogen bonding [12–15]. Halogen
bonds are weak supramolecular non-covalent interactions and
are often similar to hydrogen bonds where the hydrogen is replaced
by a halogen which acts as a halogen bond donor and are
attributed to electrostatic forces. The halocarbons can effectively
be the electropositive site that can interact with an electron donating
atom/group to produce higher dimensional structures. However,
they may also function as halogen bond acceptors forming
CAX N/O interactions as well as halogen–halogen interactions
[16–19]. This flexibility is associated with the polarizability of
the halogens which have a positive r-hole along the CAX axis
and belt of negative charge perpendicular to this CAX bond [20].
The more polarizable the halogen the stronger the interaction will
be, consequently halogen bonding typically increases on moving
from F to I.