Helicity-driven chiral self-sorting supramolecular polymerization with Ag⁺: right- and left-helical aggregates

Area of Science:

• Supramolecular Chemistry
• Chiral Materials Science
• Biomedical Applications

Background:

• Chiral self-sorting is crucial for understanding biological systems and developing biomedical applications.
• Supramolecular polymerization offers a platform for creating complex molecular architectures.
• Controlling chirality in self-assembled systems is a significant challenge.

Purpose of the Study:

• To investigate unprecedented chiral self-sorting supramolecular polymerization with helical inversion.
• To explore the role of silver ions (Ag+) in inducing chiral self-sorting in a single enantiomeric component.
• To demonstrate self-sorting driven by helicity and shape discrimination.

Main Methods:

• Synthesis of bola-type terpyridine-based ligands with R- or S-alanine analogs (R-L1 and S-L1).
• Supramolecular polymerization of R-L1 to form right-handed helical fibers (aggregate I).
• Addition of silver nitrate (AgNO3) to induce helical inversion and formation of left-handed helical aggregates (aggregate II) and spherical aggregates (aggregate III).
• Atomic Force Microscopy (AFM) and Circular Dichroism (CD) spectroscopy to analyze aggregate structures and helicity.

Main Results:

• R-L1 formed right-handed helical fibers (aggregate I) via supramolecular polymerization.
• Addition of AgNO3 to R-L1 induced a multistep process, leading to the formation of left-handed helical aggregate II ([R-L1Ag]+ complex) and metastable spherical aggregate III ([R-L1(AgNO3)2] complex).
• AFM and CD results indicated homochiral self-sorting in a mixture system through the rearrangement of aggregates I and III, forming aggregate II.
• The self-sorting was driven by helicity and shape discrimination induced by Ag+.

Conclusions:

• A unique example of helicity- and shape-driven chiral self-sorting supramolecular polymerization induced by Ag+ from a single enantiomeric component was demonstrated.
• This finding enhances understanding of homochirality in biological models.
• The study contributes to the development of novel chiral materials and catalysts for asymmetric synthesis.