Enantioselective Component Selection in Multicomponent Supramolecular Gels

We investigate a two-component acid-amine gelation system in which chirality plays a vital role. A carboxylic acid based on a second generation L-lysine dendron interacts with chiral amines and subsequently assembles into supramolecular gel fibers. The chirality of the amine controls the assembly of the resulting diastereomeric complexes, even if this chirality is relatively poor quality. Importantly, the selective incorporation of one enantiomer of an amine over the other into the gel network has been demonstrated, with the R amine that forms complexes which assemble into the most stable gel being primarily selected for incorporation: Thermodynamic control has been proven by forming a gel exclusively with an S amine, allowing the R enantiomer to diffuse through the gel network, and displacing it from the solidlike fibers, demonstrating that these gels adapt and evolve in response to chemical stimuli to which they are exposed. Excess amine, which remains unincorporated within the solidlike gel fiber network, can diffuse out and be reacted with an isocyanate, allowing us to quantify the enantioselectivity of component selection but also demonstrating how gels can act as selective reservoirs of potential reagents, releasing them on demand to undergo further reactions; hence, component-selective gel assembly can be coupled with controlled reactivity.