Sub-Stoichiometric Supramolecular Co-Assembly Strategy Enabling Efficient Chirality Transfer and CPL Amplification.

Abstract

Chirality transfer enables molecular asymmetry to propagate from discrete building blocks into hierarchical assemblies, providing a fundamental framework for engineering functional nanostructures. However, conventional supramolecular co-assembly typically necessitates stoichiometric or excess guest loading to achieve effective chirality transfer, a requirement that often compromises structural fidelity and chiroptical efficiency due to inefficient stereochemical communication. Here, we report a sub-stoichiometric co-assembly strategy wherein trace amounts of an achiral modulator (berberine, BBR) cooperatively intercalate within a chiral supramolecular framework (LPF/DPF; left-/right-handed phenylalanine-based gelators) to induce potent chiroptical amplification. We demonstrate that a minimal guest-to-host mole ratio of 0.2 is sufficient to capture and amplify host chirality, yielding luminescence dissymmetry factors (|g_lum| ≈ 0.08) an order of magnitude higher than those produced by stoichiometric equivalents. Mechanistic investigations reveal that sparse intercalation at this sub-stoichiometric threshold preserves the underlying hydrogen-bonded network while enforcing a precise helical registry through synergistic π-π and electrostatic interactions that ensures thermodynamic stability (ΔG°). While stoichiometric excess results in kinetically trapped, non-helical aggregates, this sub-stoichiometric control establishes a robust design principle for translating molecular-scale interactions into high-performance chiroptical materials with minimal guest loading.