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Abstract

The on-surface reaction of 2,3-dibromoanthracene molecules is studied on two surfaces, Au(100) and Au(111) that differ in their surface reconstructions and thus atomic-scale structure. After deposition intact molecules are observed, which form highly ordered close-packed islands, with preferential adsorption along the corrugation rows of the substrate in the case of Au(100). Heating the sample at 520 K induced Br dissociation and on-surface oligomerization of the thus activated anthracene moieties. While dimers and trimers are formed on Au(111) where they segregate into different molecular islands, only dimers are generated on Au(100). Hence, the reaction mode can be controlled on Au(100) which clearly favors the [2+2]cycloaddition product whereas the [2+2+2] cycloaddition reaction is suppressed. This high selectivity for forming the linear dimer seems to be caused by the adsorption geometry on the reconstructed Au(100) surface.