Nanoporous materials based on heteroleptic bilayers built up from bisphosphonium, p-sulfonatocalix[4]arene ions

Abstract

Sulfonatocalix[4]arene, 1, and bisphosphonium cation, 2, form extensive self-assembled arrays in the presence of lanthanide metal cations, building up new materials based on both types of ions. Systematic studies using the combinatorial approach reproducibly yielded three novel structures based on these ions. Complexes 3––5, were prepared by varying the ratio of the components, organic and metal ions, in addition to varying the pH and ionic strength of the solutions. The structural motifs in these complexes were found to be lanthanide specific and the complexes were obtained from a 1 : 1 ratio of the organic ions in the presence of an excess of lanthanide metal cations at near neutral pH. Two structures based on bilayers, 3 and 4, are accessible, differing in the ratio of the organic components, 1 and 2, 7 : 6 and 1 : 2, respectively. Complexes 3 and 4 have a supersized bilayer with 3 featuring a 2D channel system associated with a scaffolding role of the bisphosphonium cation. The structural motif in complex 5 is devoid of bilayer arrangements, instead taking on a compact structure.