Evidence of Intercolumnar π−π Stacking Interactions in Amino-Acid-Based Low-Molecular-Weight Organogels

Abstract

A comparative IR and NMR study of two low-molecular-weight organogels (LMWGs) based on aminoacid derivatives let us point out the hierarchy of the gelation assembly process. Different association states of corresponding organogelator molecules can be observed leading to the supramolecular organization of gel. A first hydrogen bond network of gelators leads to the formation of "head-to-tail" stacking-up, which can be assembled afterward one to the other by π-π stacking interactions. These small supramolecular aggregates (incipient precursor) are still visible in NMR spectra, and they represent, for example, 36% of the total amount of gelator in the case of the L-phenylalanine derivative (gelator 1) at 1 wt % in toluene. Finally, in the last step, the incipient precursor tends to form the expected 3D fibrillar network responsible for the gelation phenomenon. Temperature-dependent IR and NMR experiments allowed us to identify these different states clearly.

Creation of Chiral Thixotropic Gels through a Crown–Ammonium Interaction and their Application to a Memory‐Erasing Recycle System

“…[11,23] To further understand the thixotropic origin of studied gels IR measurements were performed on the xerogels of 1 and 1·(RR)-9 ( Figure S3 in the Supporting Information). The IR spectrum of 1 prepared by the thermal method showed stretching at 3271 and 1649 cm À1 for ñA C H T U N G T R E N N U N G (N À H) and ñA C H T U N G T R E N N U N G (C=O), respectively.…”

“…These peaks imply formation of the intermolecular amide C=O···HÀN hydrogen-bonding network. [11,23] The gel sample of 1·(RR)-9 prepared by the thermal method showed weak N À H stretching at 3300 and C=O stretching at 1666 cm…”

Self-Assembled Fluorinated Organogelators for Surface Modification

“…This complex process of self-assembly into supramolecular structures varies based on the functionalities present in the organogelator and external factors, including solvent, temperature, and pH. Various non-covalent interactions, such as hydrogen bonding, π-π stacking, hydrophobic interactions, and metal coordination, influence the formation and stabilization of the organogelator self-assemblies [1,2,[10][11][12][13][14][19][20][21]. However, the non-covalent forces influencing gelation are relatively weak compared to covalent bonds, and a combination of many of these interactions is required to form a strong intermolecular network.…”

“…The design and elucidation of structure-property relationships of gelators is also a valuable area of research, in particular, establishing the relationship between the chemical structure of a gelator and its gelation properties in a given solvent [10][11][12][13][14][15][16][17][18]. Thermally reversible physical gels are generally formed by self-assembly of the gelator molecules in solvent, leading to the…”

Design, synthesis and stimuli responsive gelation of novel stigmasterol–amino acid conjugates

“…Solution NMR experiments have been extensively used to understand the possible interactions involved in the process of gelation [17,20,[34][35][36][37][38]. Attempts have also been made recently to study details to extract the self-assembled structural information at various stages of gelation [34,35].…”