When depositing a Polyciclic Aromatic Hydrocarbon (PAH) on different transition metals, the presence or the lack of diffusion of the as-deposited precursor rules the final outcome of the surface-assisted dehydrogenation. When diffusion is allowed, on weakly interacting surfaces, the pyridyl-substituted dibenzo[5]helicene (DiPy[5]DBH) can form N-doped networks by dehydrogenative polymerisation. When no diffusion occurs, no interaction with other molecules is allowed: upon thermal activation, the lack of annealing results in surface-assisted intramolecular cyclodehydrogenation, so new 0D objects are created.
DiPy[5]DBH diffuses when deposited on Cu(110). In these videos we show the initial stages of the formation of N-doped organic chains on Cu(110), obtained after annealing the system to 200ºC. The molecules dehydrogenate and meet other dehydrogenated molecules upon diffusion, so that C dangling bonds of different precursors can bond together to form chains.
In these videos, we can see some dimers and oligomers which are the seeds of the polymeric chains. The other precursors, the ones which did not dehydrogenate, are still diffusing: they mostly move in the direction of the rows of Cu(110), because the energy needed to change row is higher than the energy they dispose, hence choosing the row direction as the preferential one.