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.