Spherical shape complementarity as an overriding motif in the molecular recognition of noncharged organic guests by p-sulfonatocalix[4]arene: Complexation of bicyclic azoalkanes

P-sulfonatocalix[4]arene that was demonstrated to display a relatively moderate guest size selectivity for inclusion of bicyclic guests is described. It was found that azoalkanes are highly water-soluble and display substantially higher binding constants than previously investigated noncharged organic guest molecules.