Ionic Bent-Core\nPillar[<i>n</i>]arenes:\nFrom Liquid Crystals to Nanoaggregates and Functional Applications

Herein, we report the first examples of supramolecular\nsystems\nfrom bent-core-based pillar[<i>n</i>]arenes through ionic\nbonds. These ionic materials have been prepared by the interaction\nof an amino-ended pillar[5]arene (P5N10) and three different carboxylic\nacids, including bent-core moieties. The bent-core units are based\non ester, biphenyl, and azobenzene structures bearing two different\nflexible spacers between the carboxyl group and the central bent-core\naromatic units. The ionic pairs segregate the molecular blocks, leading\nto columnar liquid crystal organizations. These ionic supramolecular\ncompounds exhibit interesting results as proton-conductive materials.\nFurthermore, the introduction of azobenzene units in the bent-core\nstructure has provided a photoresponse to the proton conduction materials.\nInterestingly, the amphiphilic character generated by the ionic pairs\nand the hydrophobic bent-core structures allows their molecular self-assembly\nin water solution, resulting in aggregates of appealing morphologies.\nThe structural modifications of the bent-core units (i.e., connecting\nbonds at the lateral structure and spacer lengths) provide an attractive\nanalysis on the relationship between the chemical structure and the\nmorphology of the aggregates (fibers, chiral ribbons, nanotubes...).\nAdditionally, the self-assembly process and evolution of the aggregates\nfrom fibers to nanotubes have been studied with several techniques.