Selective decarboxylative dimerization enabled by a supramolecular template on Ag(111)

Area of Science:

• Surface science
• Organic chemistry
• Supramolecular chemistry

Background:

• On-surface synthesis faces challenges in achieving high selectivity.
• Controlling reaction pathways in multi-functional molecules on surfaces is complex.

Purpose of the Study:

• To investigate the decarboxylative coupling reactions of heptaazaphenalene-tribenzoic acid (HTBA) on the Ag(111) surface.
• To understand how supramolecular assembly influences reaction selectivity.

Main Methods:

• Scanning Tunneling Microscopy (STM) for temperature-dependent measurements.
• In situ heating to observe reaction dynamics.
• Control experiments under pseudo-high dilution conditions.

Main Results:

• A thermally persistent supramolecular ribbon assembly of HTBA was formed on Ag(111).
• Sequential annealing predominantly (>90%) yielded a single dumbbell-shaped dimer from HTBA.
• Anisotropic steric confinement and inter-ribbon displacement within the assembly directed selectivity.
• Dimer formation was suppressed under pseudo-high dilution, confirming templating effects.

Conclusions:

• Supramolecular organization can effectively regulate reaction selectivity in multi-functional molecules on surfaces.
• Molecular templating within stable assemblies provides a strategy for high-selectivity on-surface synthesis.
• The study offers mechanistic insights into surface-confined reaction control.