Novel Low-Molecular-Weight Gelators Based on Azobenzene Containing l-Amino Acids

A series of azobenzene derivatives containing glycine, l-alanine, l-valine, l-leucine, and l-isoleucine were synthesized and their gelation properties were examined. Although the azobenzene derivatives containing glycine, l-alanine, and l-leucine exhibited very low gelation abilities, other compounds of l-isoleucine and l-valine acted as good gelators that formed organogels in many organic solvents and oils at relatively low concentrations. The electron microscopic observation demonstrated that a three-dimensional network was created by entanglement of self-assembled nanofibers. Furthermore, the spectroscopic studies suggested that the gelator molecules self-assembled into the nanofibers through hydrogen bonding and π–π interactions, including the H-aggregation mode of the azobenzene segments.