Mesoscale Assembly of Bisteroidal Esters from Terephthalic Acid

Abstract

A new series of bisteroidal esters was synthesized using a spacer group, sterols and sapogenins as substrates. Steroidal dimers were prepared in high yields employing diesters of terephthalic acid as linkages at the 3β, 3′β steroidal positions. In all attempts to crystallize bisteroids, it was observed that the compounds tended to self-organize in solution, which was detected when employing various solvent systems. The non-covalent interactions (van der Waals) of the steroidal moieties of this series of symmetrical bisteroids, the polarity of the solvents systems, and the different solubilities of the bisteroid aggregates, indeed induce the molecules to self-assemble into supramolecular structures with well-defined organization. Our results show that the self-assembled structures for the bisteroidal derivatives depend on the solvent system used: with hexane/EtOAc, membrane-shaped structures were obtained, while pure EtOAc afforded strand-shaped arrangements. In the CHCl3/CH3OH system, thin strands were formed, since van der Waals interactions are lowered in this system, as a consequence of the increased solubility of the bisteroids in CHCl3. Based on the characterization by SEM and XRD, we show evidence that the phenomenon of self-assembly of bisteroids occurs presenting different morphologies depending on the solvent used. The new steroidal dimer derivatives were characterized by NMR, TGA, DSC, SEM, and XRD. Finally, the molecular structure of one bisteroid was confirmed by single-crystal X-ray analysis.

[60]Fullerene Hybrids Bearing “Steroid Wings”: A Joined Experimental and Theoretical Investigation

“…The presence of two steroid moieties in compound 5 seems to induce molecules to self‐assemble into more organized supramolecular structures allowing a better control of the size of the nanoparticles, but also minimizing the formation of conglomerates or nanoparticle networks. Related studies have been recently published showing that non‐covalent interactions (van der Waals forces) among the steroid residues of symmetric bi‐steroids derived from terephthalic acid, but also the polarity of the solvent, promoted the self‐assembly of the molecules into organized mesoscale supramolecular structures …”

“…Related studies have been recently published showing that non-covalent interactions (van der Waals forces) among the steroid residues of symmetric bi-steroids derived from terephthalic acid, but also the polarity of the solvent, promoted the self-assembly of the molecules into organized mesoscale supramolecular structures. [45] On the other hand, in order to assess the intramolecular electrostatic interactions in hybrids 4 and 5, a conformational search was carried out by calculating the electron density that surround each molecular hybrid. Thus, molecular electrostatic potential maps were obtained, as depicted in Figure 6.…”