Thermal Annealing Triggered Chirality Inversion through Solvent Migration

Solvent strategy is a powerful tool to manipulate chirality and self-assembly over hierarchical levels, yet the solvent dynamics during thermal annealing in controlling chirality and chiroptical features remain a mystery. Here, we show how solvent migration affects molecular folding and chirality through thermal annealing. Pyrene segments were conjugated to a 2,6-diamide pyridine skeleton, where intramolecular hydrogen bonds anchor the chiral geometry. The orientation of pyrene blades adopted pi center dot center dot center dot pi and CH center dot center dot center dot pi stacking, respectively, in organic solvents (dimethyl sulfoxide, DMSO) and aqueous media, leading to the chiroptical inversion. Thermal annealing treatment of the DMSO/H2O mixture homogenized distribution of solvents that further altered the molecular folding from CH center dot center dot center dot pi to pi center dot center dot center dot pi modality. Solvent migration from aggregates to bulky phases was evidenced by the nuclear magnetic resonance and molecular dynamic simulations, leading to the rearrangement of molecular packing with luminescent changes. It realized a consecutive chiroptical inversion using solvent strategy and thermal annealing.