On-Surface Photodissociation Control within Magic-Sized Nanoclusters by Halogen Bonding

Area of Science:

• Surface Science
• Supramolecular Chemistry
• Photochemistry

Background:

• On-surface synthesis often uses self-assembly and dissociation of halogen-substituted molecules.
• Understanding molecular interactions on surfaces is key for controlled reactions.
• Halogen bonding plays a role in molecular assembly and reactivity.

Purpose of the Study:

• To investigate the influence of halogen bonding on the photolytic dissociation of bromobenzene nanoclusters on a Cu(111) surface.
• To elucidate the role of cluster size and noncovalent interactions in surface-mediated reactions.
• To explore the potential of weak interactions for guiding selective photolytic reactions.

Main Methods:

• Utilized two-photon photoemission spectroscopy (2PPE) to study electronic properties.
• Employed scanning tunneling microscopy (STM) for atomic-scale surface imaging.
• Performed density functional theory (DFT) computations to model interactions and reaction pathways.

Main Results:

• Identified magic-sized tetramer nanoclusters of bromobenzene on Cu(111) stabilized by halogen and weak hydrogen bonding.
• Demonstrated that surface adsorption enhances halogen bonding while weakening hydrogen bonds.
• Showed that tetramers facilitate bromobenzene photodissociation via work function reduction, with exterior molecules dissociating preferentially.

Conclusions:

• Weak noncovalent interactions, particularly halogen bonding, are crucial for directing the size and reactivity of molecular nanoclusters on surfaces.
• The specific arrangement in tetramers enables selective photolytic dehalogenation of bromobenzene.
• This work highlights the potential of controlling surface reactions through tailored molecular assembly and weak interactions.