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Tuning Dehalogenative Coupling of Br2Py on Bimetallic Templates.
Jinping Hu1,2, Hongbing Wang1,2, Zhaofeng Liang3
1Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201204, China.
Langmuir : the ACS Journal of Surfaces and Colloids
|October 24, 2022
Summary
This study explores Ullmann coupling on bimetallic surfaces, specifically Bi-Ag(111) and Bi-Au(111). Bismuth adatoms on silver surfaces enable controlled polymerization, while on gold surfaces, higher temperatures are needed for coupling reactions.
Area of Science:
- Surface Science
- Nanotechnology
- Organic Chemistry
Background:
- On-surface Ullmann coupling is crucial for synthesizing nanostructures.
- Previous studies focused on single-metal surfaces, limiting control over reactions.
- Bimetallic surfaces offer potential for novel reactivity and control.
Purpose of the Study:
- To investigate the Ullmann coupling of 2,7-dibromopyrene (Br2Py) on bimetallic Bi-Ag(111) and Bi-Au(111) surfaces.
- To understand the role of bismuth adatoms in modifying surface reactivity and reaction pathways.
- To explore the potential of bimetallic systems for controlled on-surface polymerization.
Main Methods:
- Scanning Tunneling Microscopy (STM) for atomic-scale visualization.
- X-ray Photoemission Spectroscopy (XPS) for chemical state analysis.
- Controlled annealing experiments on bimetallic substrates.
Main Results:
- On Bi-Ag(111), intact Br2Py self-assembly occurs, followed by dehalogenation and polymerization upon annealing, with Bi adatoms having minimal impact on coupling.
- Post-deposition of Bi onto Ag(111) nanostructures initiates Ullmann coupling, leading to polymer chains with altered structures compared to bare Ag(111).
- On Bi-Au(111), higher annealing temperatures are required for Ullmann coupling, and the C-C coupling reaction is resistant to Bi adatoms, with Bi-Au reconstruction recovery observed.
Conclusions:
- Bimetallic surfaces provide a versatile platform for controlling Ullmann coupling reactions.
- Bismuth adatoms significantly influence the self-assembly and polymerization of organic molecules on silver and gold surfaces.
- This work offers insights into reaction mechanisms and a new strategy for designing platforms for regulated Ullmann coupling.
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