Amplification of asymmetry in complex molecular systems
results
from a delicate interplay of chiral supramolecular structures and
their chemical reactivity. In this work, we show how the helicity
of supramolecular assemblies can be controlled by performing a non-stereoselective
methylation reaction on comonomers. By methylating chiral glutamic
acid side chains in benzene-1,3,5-tricarboxamide (BTA) derivatives
to form methyl esters, the assembly properties are modulated. As reacted
comonomers, the methyl ester-BTAs induce a stronger bias in the screw-sense
of helical fibers predominantly composed of stacked achiral alkyl-BTA
monomers. Hence, applying thein situmethylation
in a system with the glutamic acid-BTA comonomer induces asymmetry
amplification. Moreover, mixing small quantities of enantiomers of
glutamic acid-BTA and glutamate methyl ester-BTA in the presence of
the achiral alkyl-BTAs leads to deracemization and inversion of the
helical structures in solutionviathein
situreaction toward a thermodynamic equilibrium. Theoretical
modeling suggests that the observed effects are caused by enhanced
comonomer interactions after the chemical modification. Our presented
methodology enables on-demand control over asymmetry in ordered functional
supramolecular materials.