Cross-coupling of aryl-bromide and porphyrin-bromide on an Au(111) surface

Abstract

Cross-coupling is of great importance in organic synthesis. Here it is demonstrated that cross-coupling of aryl-bromide and porphyrin-bromide takes place on a Au(111) surface in vacuo. The products are oligomers consisting of porphyrin moieties linked by p-phenylene at porphyrin's meso-positions. The ratio of the cross-coupled versus homocoupled bonds can be regulated by the reactant concentrations. Kinetic Monte Carlo simulations were applied to determine the activation barrier. It is expected that this reaction can be employed in other aryl-bromide precursors for designing alternating co-polymers incorporating porphyrin and other functional moieties. Back on the chain gang: Aryl-bromide and porphyrin-bromide cross-coupling on an Au(111) surface with a yield as high as 95% was achieved, as confirmed by submolecularly resolved scanning tunnelling microscopy imaging (see figure). Tuning the ratio of the two reactants allowed formation of 95% of the cross-coupled bonds. The activation barriers were determined using kinetic Monte Carlo simulations.