Manipulation of C-C coupling pathways using different annealing procedures.

From scanning tunnelling microscopy and density functional theory calculations, we demonstrate that different annealing mechanisms could modulate distinct reaction pathways, where in a stepwise annealing procedure the detached Br atoms may reduce the activation barrier of CH activation resulting in hierarchical cross dehydrogenative coupling, while in a one-step annealing procedure only Ullmann coupling products are observed.