Solid-State Examination of Conformationally Diverse Sulfonamide Receptors Based on Bis(2-anilinoethynyl)pyridine, -Bipyridine, and -Thiophene

Utilizing an induced-fit model and
taking advantage of rotatable
acetylenic C­(sp)–C­(sp2) bonds, we disclose the synthesis
and solid-state structures of a series of conformationally diverse
bis-sulfonamide arylethynyl receptors using either pyridine, 2,2′-bipyridine,
or thiophene as the core aryl group. Whereas the bipyridine and thiophene
structures do not appear to bind guests in the solid state, the pyridine
receptors form 2 + 2 dimers with water molecules, two halides, or
one of each, depending on the protonation state of the pyridine nitrogen
atom. Isolation of a related bis-sulfonimide derivative demonstrates
the importance of the sulfonamide N–H hydrogen bonds in dimer
formation. The pyridine receptors form monomeric structures with larger
guests such as BF4– or HSO4–, where the sulfonamide arms rotate to the side
opposite the pyridine N atom.