Imidazolium-based [14]heterophanes as models for anion recognition

The significance of the reported dicationic [1(4)]imidazoliophanes 4(.)2X relies on their ability to bind anions in polar media. Thus, imidazolium units represent the main structural motifs in the formation of unconventional (C-H)+center dot center dot center dot Cl(-)charge-assisted hydrogen bonds which become the noncovalent forces driving the anionic interactions exhibited by dications 4.2X. Herein, we report the "3+1" convergent synthesis of the title macrocycles 4a-d(.)2X; their counteranion exchange using a strongly basic anion-exchange resin (OH- form) and their structures have been examined by NMR spectroscopy. Solution studies in CD3CN and [D-6]DMSO by H-1 NMR spectroscopy have revealed the importance of the hydrogen bonds in controlling anion recognition. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)