Local Solvent Ordering Drives Supramolecular Chirality Inversion.

Solvent composition is widely assumed to influence supramolecular chirality indirectly through bulk properties such as polarity or solvophobicity. Here, we show that local solvent organization can directly dictate chiral pathway selection and invert supramolecular helicity. A chiral perylene bisimide bearing L-phenylalanine substituents (L-PhePBI) undergoes a complete reversal of helical sense in water/DMSO mixtures upon a narrow change in solvent composition (Δfwater = 0.2), despite maintaining a similar degree of aggregation. The comparable polarity of the two solvent compositions excludes bulk solvent effects as the origin of this stereomutation. Molecular dynamics simulations reveal that solvent-composition-dependent reorganization of the first hydration shell biases molecular twist angles within stacked assemblies, thereby selecting opposite chiral pathways. Variable-temperature spectroscopic studies further identify a kinetically trapped chiral state that irreversibly converts to a thermodynamically stable enantiomorph upon heating. This thermal inversion is associated with a redistribution of hydrogen bonding from nearest-neighbor to nonadjacent molecular pairs, stabilizing a distinct packing motif. Together, these results establish a direct mechanistic link between local solvent ordering, noncovalent interaction reorganization, and supramolecular stereomutation, demonstrating solvent composition as a precise control parameter for programming chiral organization in supramolecular materials.