Structural Effects of Peptide-Type Amines on Ambidextrous Gelation Properties and Their Application to Chiral Recognition.

Amino acid-based low-molecular-weight gelators (LMWGs) attract considerable attention for the construction of supramolecular gels with controlled properties. Although most LMWGs behave as either organogelators or hydrogelators, several ambidextrous LMWGs have been reported. However, the factors determining this ambidextrous nature are unclear. Considering that structural differences between LMWGs affect their molecular assembly and gelation ability, analogues of chiral peptide-type amines were developed as LMWGs in this study to investigate the structural effects on their ambidextrous gelation properties. LMWGs with longer spacers behaved as only organogelators and lost their ambidextrous nature. Although the different structures of amide bonds (NHCO or CONH) decreased the ambidextrous nature, replacing one amide group with a urea moiety improved the ambidextrous gelation ability owing to the formation of stronger hydrogen bonds. The self-assembled structures of the gelators were examined, and the relationship between the structure and the gelation ability was elucidated. Finally, the application of the supramolecular gel derived from the LMWGs to the chiral recognition of a carboxylic acid was demonstrated.