No abstract

meta-Phenylene bis(phenylurea) receptors 1-4 were designed and synthesized to investigate the association between receptor shape, anion-selective binding and anion-directed self-assembly processes. Solution studies, performed through H NMR titrations with a variety of tetra- N-butylammonium salts, demonstrated strong binding of 2 equiv of HPO, AcO, BzO anions and comparatively weak binding of Cl, HSO, and SO anions. Binding modes and stability constants (log β) were determined by regression analysis of the obtained H NMR titration data in DMSO- d, and the cooperativities of the binding interactions were probed. Host-guest complexes of receptors 1 and 2 were studied in the crystalline phase to further probe the anion-binding behavior of this motif. This included a triple-stranded helicate consisting of three strands of receptor 2 arranged around a mixed-phosphate anionic core, which was characterized by using X-ray crystallography.