Supramolecular Organogels Stimulated by Anions

Abstract

Nanoscale self-assemblies of pi-conjugated acyclic receptors can be modulated by external chemical stimuli. Of the acyclic anion receptors, C₃-bridged oligopyrroles with pi-conjugated planar structures show efficient anion binding by means of NH and bridging CH sites with inversion of two pyrrole rings. Aryl-substituted receptors have been obtained in 80-90% from the corresponding arylpyrroles and malonyl chloride in CH₂Cl₂ and subsequent treatment with BF₃OEt₂. Binding mode using NH, bridging CH, and o-CH has been confirmed by 1H NMR, DFT calculations, and X-ray analyses. Based on pi-pi stacking structure in solid state of methoxy substituted derivative, the derivatives with long alkyl chains yield supramolecular organogels from octane, which are transformed to solution state by addition of anion.