Fabrication and regulation of self-assembled nanostructures of benzene-1,3,5-tricarboxamide derivatives

A variety of supramolecular structures of benzene-1,3,5-tricarboxamide derivatives (BTAs), such as helixes and nanosheets , have been fabricated. However, how to regulate the self-assembly behavior through molecular design and control of experimental conditions, and thus to form supramolecular structures with different morphologies is still a topic that needs to be further explored. In this paper, two kinds of BTAs with different end groups, i.e. terpyridine and carboxyl were synthesized, which are referred to as L and A, respectively. Their self-assembly behaviors in DMF/aqueous solution were investigated by adding the DMF solution of BTAs into the aqueous solution dropwise. It was found that the two BTAs exhibited different self-assembly behaviors. L self-assembled into helical nanowires and nanosheets in the mixed media at lower and higher metal ion concentrations. However, A formed multilayer vesicles and nanotubes at lower and higher concentrations of A molecules. Such a difference was ascribed to their different molecular structures and therefore the different amphiphilicity. The more hydrophobic L molecules could escape from DMF droplets and self-assembled with the help of supramolecular interactions. The more amphiphilic A molecules were prone to adsorb at the oil/water interface to form layered films. The relative strength of coordination interaction determined the self-assembly behavior of L and the formation of helical nanowires and nanosheets , and the packing mode of A molecules at the oil/water interface determined the formation of vesicles and nanotubes . In addition, the formed vesicles of A were responsive to pH.