Crystallographic and solution anion binding studies of bis-amidofurans and thiophenes

A variety of furan and thiophene amide and thioamide cleft type anion receptors have been synthesised and crystallographically characterised. Unlike 2,5-diamidopyrrole anions, analogous 2,5-diamidofurans and thiophenes do not interlock in the solid state. The anion binding properties of these receptors have been investigated in DMSO/0.5% water solution using H-1 NMR titration techniques. Solution studies and solid-state evidence suggests that the thiophene receptors may utilise a thiophene CH hydrogen atom for hydrogen bond formation to anions with a 2,4-diamidothiophene showing similar anion binding affinities to a 2,5-diamidopyrrole.