Molecular recognition of melamine and cyanuric acid by C2-symmetric phenylalanine based supramolecular hydrogels

Abstract

Molecular recognition of achiral structural analogues, a remaining challenge for materials scientists and chemists, is the key to manipulating the applications and properties of supramolecular chiral materials. Herein, we report the molecular recognition of two harmful structural analogues i.e. melamine (MA) and cyanuric acid (CA) by using C2-symmetric phenylalanine chiral hydrogelators. Two distinct molecular recognition events between hydrogelator fibrils and triazine based achiral molecules are demonstrated: phenylalanine-co-melamine (PF-co-MA) gels showed chirality amplification while chirality inversion was observed for phenylalanine-co-cyanuric acid (PF-co-CA) gels. Moreover, viscoelastic properties and twist pitch were also regulated under the influence of the achiral molecules. Such phenomenon is mainly mediated by H-bonding among the two components, which may subtly change the arrangement of the molecules, in turn, the self-assembled nanostructures. This method of using C2-symmetric phenylalanine based gelators in the recognition of the achiral molecules may be broadly applicable for a wide variety of molecular recognition partners such as sugars.