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Dissymmetric On-surface Dehalogenation Reaction Steered by Preformed Self-assembled Structure.

Ullmann coupling of 4,4''-dibromo-p-terphenyl (DBTP) thermally catalyzed on Ag(111) surface was studied by scanning tunneling microscopy. Detailed experimental measurement shows that the Ullmann coupling reaction pathways of DBTP molecules can be controlled by pre-self-assembly, and the dissymmetric dehalogenation reaction is realized. Moreover, self-assembly of the reactants in rectangular network undergoes an dissymmetric debromination transfer to a newly-observed rhombic network formed by organometallic dimers prior to the formation of longer symmetric organometallic intermediates on Ag(111) surface, while the ladder assembled phase is more likely to induce symmetric debromination reaction and convert into the symmetric organometallic intermediate. These findings help us to understand the essential of dissymmetric dehalogenation reaction originated from symmetric compound and pave new avenues for advancing the emerging field of on-surface synthesis.