Steering the Achiral into Chiral with a Self-Assembly Strategy

Area of Science:

• Surface Science
• Supramolecular Chemistry
• Chirality Studies

Background:

• Phthalocyanines are versatile macrocyclic compounds with applications in various fields.
• Achiral molecules can exhibit chirality through specific interactions or assembly processes.
• Understanding chirality transfer is crucial for developing chiral materials and devices.

Purpose of the Study:

• To investigate the transfer of chirality from self-assembled achiral titanyl phthalocyanine (TiOPc) to adsorbed molecules.
• To elucidate the mechanism behind chirality induction in achiral molecules upon adsorption.
• To explore the general applicability of this chirality transfer phenomenon.

Main Methods:

• Self-assembly of achiral titanyl phthalocyanine (TiOPc) on a Au(111) surface.
• Scanning Tunneling Microscopy (STM) for structural characterization.
• Density Functional Theory (DFT) calculations to analyze electronic structure and charge transfer.

Main Results:

• Achiral TiOPc molecules self-assemble into a porous network with chiral voids on Au(111).
• A top-sitting TiOPc molecule adsorbed in a chiral void becomes chiral.
• Chirality arises from charge transfer between the indole rings and oxygen atoms, leading to chiral molecular orbitals.
• Other achiral metallophthalocyanines, like copper phthalocyanine, also exhibit induced chirality.

Conclusions:

• Chirality can be successfully transferred from a self-assembled achiral molecular network to individual adsorbed molecules.
• The mechanism involves the formation of chiral voids and subsequent charge transfer, inducing molecular chirality.
• This finding suggests a general pathway for creating chiral structures from achiral building blocks.