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

Abstract

The supramolecular oligomerization of three water-soluble C(3)-symmetrical discotic molecules is reported. The compounds all possess benzene-1,3,5-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 H(2)O. 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.

Paramagnetic self‐assembled nanoparticles as supramolecular MRI contrast agents

“…Gadomer 17, r 1 ≈ 15 m m −1 s −1 ) . Concentration‐dependent relaxation rate ( R 1 ) measurements have been shown to be a useful technique to study the aggregation behavior of supramolecular systems, for example to determine the critical aggregation of micelles, but also to study the self‐assembly of paramagnetic discotics . Upon dilution, the slope of the profiles, defined as relaxivity r 1 , changes gradually, which is in line with our previous investigations .…”

“…Concentration‐dependent relaxation rate ( R 1 ) measurements have been shown to be a useful technique to study the aggregation behavior of supramolecular systems, for example to determine the critical aggregation of micelles, but also to study the self‐assembly of paramagnetic discotics . Upon dilution, the slope of the profiles, defined as relaxivity r 1 , changes gradually, which is in line with our previous investigations . Below 8 µ m discotic concentrations [24 µ m Gd(III)], the presence of smaller oligomers and monomers starts to dominate the self‐assembly behavior and the relaxivity values r 1 drop below 8 m m −1 s −1 (Fig.…”

“…) . By balancing out these positive interactions with electrostatic repulsive contributions from charged Gd(III)–DTPA chelates, the self‐assembly yielded supramolecular oligomers of controlled shape and size, whereas the introduction of fluorinated aromatics increased the aggregate stability by about an order of magnitude . Because of their high stability and hydrodynamic radius ( R H ) in the nanometer range (<5 nm), this unique system is predisposed to be evaluated as a macromolecular Gd(III)‐based MRI contrast agent, most suitable for blood pool imaging applications.…”

Self‐Assembly Studies of a Chiral Bisurea‐Based Superhydrogelator

“…In this sense, it is well known that molecules that contain a defined hydrophobic core and peripheral polar groups allow for their self-assembly into stable columnar aggregates. [8] Furthermore, the effects of the chirality of the peripheral hydroxy groups on the hydrogelation characteristics of compound 1, as well as of achiral bisurea 2, have Abstract: A chiral bisurea-based superhydrogelator that is capable of forming supramolecular hydrogels at concentrations as low as 0.2 mm is reported. This soft material has been characterized by thermal studies, rheology, X-ray diffraction analysis, transmission electron microscopy (TEM), and by various spectroscopic techniques (electronic and vibrational circular dichroism and by FTIR and Raman spectroscopy).…”

Controlling the Size, Shape and Stability of Supramolecular Polymers in Water

“…By balancing electrostatic repulsive interactions on the hydrophilic rim and attractive non-covalent forces within the hydrophobic core of the polymerizing building block, we manage to create small and discrete spherical objects 6,7 . Increasing the salt concentration to screen the charges induces a sphere-to-rod transition.…”