Structural diversity of methyl-substituted inclusion complexes of calix[5]arene

The three isomers of xylene form inclusion complexes with p-H-calix[5]arene with different spatial interplay of the cavitands, which is relevant to using crystallization as a means of separating mixtures of o-, m-, and p-xylenes. Competition experiments involving mixtures of o-/m-xylene, o-/p-xylene, and m-/p-xylene and a mixture of all three isomers showed some selectivity in the inclusion of the xylenes with p-H-calix[5]arene according to the inequality m- > o- > p-xylene. Also reported are the toluene and mesitylene solvates, which are isostructural with the o-xylene and m-xylene inclusion complexes, respectively.