Controlled Supramolecular Oligomerization of C3-Symmetrical Molecules in Water: The Impact of Hydrophobic Shielding

The supramolecular oligomerization of three water-soluble C-3-symmetrical discotic molecules is reported. The compounds all possess benzene1,3,5-tricarboxamide cores and peripheral Gd-III-DTPA (diethylene triamine pentaacetic acid) moieties, but differ in their linker units and thus in their propensity to undergo secondary interactions in H2O. The self-assembly behavior of these molecules was studied in solution using circular dichroism, UV/Vis spectroscopy, nuclear magnetic resonance, and cryogenic transmission electron microscopy. The aggregation concentration of these molecules depends on the number of secondary interactions and on the solvophobic character of the polymerizing moieties. Hydrophobic shielding of the hydrogen-bonding motif in the core of the discotic is of paramount importance for yielding stable, helical aggregates that are designed to be restricted in size through anti-cooperative, electrostatic, repulsive interactions.