One-dimensional self-assembly of phenylacetylene macrocycles: effect of peripheral substituents.

Tetra- and tri-substituted m-phenylacetylene macrocycles with diethylene glycol monoethyl ether (DEG) phenylether peripheral side chains (PAM 1 and PAM 1') were synthesized, and both of them could self-assemble into well-defined one-dimensional (1D) structures through two kinds of fabrication processing. The recrystallization approach led to similar microbelts for PAMs 1 and 1' with hundreds of microns in length, 2-4 μm in width, and 200-300 nm in thickness. But AFM, XRD, and spectrum characterizations indicated that the microbelts of PAM 1' had smaller intercolumnar distances and more favorable π-π stacking. Two different nanostructures were obtained through the other processing of solvent evaporation: nanobelts for PAM 1 and twisted nanorods for PAM 1'. The different molecular arrangement and nanostructures could be ascribed to the different molecular structures, especially the different positioning of the peripheral substituents. This research provides a potential control over the morphology and the structure of the 1D assembly by adjusting the molecular structure as well as the sample processing.