The effect of meta versus para substitution on the aggregation of bis-cholesteryl appended 2,6-disubstituted pyridine-based gelators

Abstract

The effect of meta versus para substitution on the aggregation of bischolesteryl appended 2,6-disubstituted pyridine-based gelatorsThe structurally isomeric, bent core, 2,6-disubstituted pyridine derivatives (PyPC and PyMC) were synthesized, and their gelation ability and aggregation behavior in different solvents were studied using various techniques including electron microscopy (TEM and SEM) and X-ray diffraction analysis (XRD). The PyPC was found to be soluble in most of the organic solvents studied, which may be due to the possible existence of intramolecular hydrogen bonding in PyPC (low angle) that enhanced its solubility. In contrast, 10 the PyMC was less soluble, making it a more efficient gelator than PyPC. The results from the morphological studies showed that the xerogel of PyPC in dodecanol exhibited a nanotube morphology (diameter ~70 nm), whereas PyMC in dodecanol exhibited a fibrous morphology, indicating that the existence of positional isomerism had a profound effect on the aggregation of the molecules in solution.Both right-and left-handed helical structures were observed in all gelators; however, left-handed structures were more predominant.Intermolecular hydrogen bonding as well as π-π stacking cooperatively played an important role in the aggregation of the gelators as 15 evidenced by XRD and temperature-dependent 1 H-NMR spectroscopy analyses. Based on these results, aggregation mechanisms were proposed.

Towards supramolecular nanostructured materials: control of the self-assembly of ionic bent-core amphiphiles

“…Moreover, the ability of bent-shaped mesogens to promote supramolecular aggregates, including chiral objects, by selfassembly in a solvent has also been reported. Encouraged by the first publications by Ho and Hsu et al [52,53] and also by reports of physical gel formation by bent-shaped molecules, [54][55][56][57] the possibility of creating bent-core assemblies that form supramolecular structures in solution is now a hot target to explore. However, despite the previously listed examples, this field is still taking its first steps and comprehensive studies to understand globally both the self-assembly in bulk and in solution are yet required.…”

Self‐Assembly of Hollow Organic Nanotubes Driven by Arene Regioisomerism

“…Nevertheless, one drawback that hampers the rapid evolution of this field is the lack of organic structures capable of creating S‐ONTs during the gel formation process. Among the studies published in this area, a few S‐ONTs are formed in organic solvents, [10–15] whereas most examples involve the use of protic solvents (water, [16–18] AcOH [5–8] and alcohols [9,19] ) or auxiliary metals [20] …”

“…Nevertheless, one drawback that hampers the rapid evolution of this field is the lack of organic structures capable of creating S-ONTs during the gel formation process. Among the studies published in this area, a few S-ONTs are formed in organic solvents, [10][11][12][13][14][15] whereas most examples involve the use of protic solvents (water, [16][17][18] AcOH [5][6][7][8] and alcohols [9,19] ) or auxiliary metals. [20] Moreover, we realized that in many studies related to the formation of S-ONTs, there was a di-or polysubstituted aromatic moiety involved in the process.…”