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.