Supramolecular Recognition and Energy Frameworks in Host–Guest Complexes of 18-Crown‑6 and Sulfonamides

Crystalline
molecular complexes of 18-crown-6 with three sulfonamide
analogues (methane, benzene, and toluene sulfonamides) have been synthesized
and characterized. Among these, the 18-crown-6:benzenesulfonamide
complex exhibits three crystal forms, including a polymorphic pair.
Interaction energy calculations show that the host–guest binding
energies in these complexes are very high (∼92–104 kJ·mol–1). Energy framework analysis identifies the hierarchy
of intermolecular interactions and their topology; a trimeric motif
formed by two guest molecules and a crown host is found to be a salient
structural feature in these complexes. This study establishes the
“sulfonamide-crown motif” as a very robust and predictable
supramolecular recognition unit.