Adamantyl aminoguanidines as receptors for oxo-anions

Novel adamantyl mono- and bis-aminoguanidine receptors were prepared and their binding of selected oxo-anions was studied by means of ¹H NMR titrations. The studied receptors showed a preference towards oxo-anions when compared to the spherical iodide due to the binding pattern involving parallel hydrogen bonds. The binding affinities were correlated with the structural features of the molecules using theoretical calculations. It was found that the additional amino group from the aminoguanidine moiety could have a major role in complex binding modes of the receptors because it enables simultaneous binding of two oxo-anions to one aminoguanidine subunit.