Resorcinarenes are hexameric capsules in solution

The host-guest complexes of resorcin4arenes with small molecules in organic solutions are examined using modern NMR spectroscopic methods. The complexation of glutaric acid and beta-methyl d-glucopyranoside in chloroform were investigated through 2D COSY, 2D NOESY, 1D NOE, and diffusion-ordered NMR spectroscopy (DOSY) techniques. These methods indicate that the complex is a self-assembled capsule composed of six resorcinarenes that surround six guest molecules of glutaric acid or three molecules of beta-methyl d-glucopyranoside inside. The multiplicity of guest proton signals shows that the capsule provides an asymmetric magnetic environment that persists on the (1)H NMR time scale. The encapsulation of these guests and common solvents suggests that the phenomenon of reversible encapsulation in chemistry may be a century old.