  Understanding the nature and hierarchy of on surface reactions is a major
chal- lenge for designing coordination and covalent nanostructures by means of
multistep synthetic routes. In particular, intermediates and final products are
hard to predict since reaction paths and their activation windows depend on the
choice of both the molecular precursor design and the substrate. Here we report
a systematic study of the effect of the catalytic metal surface to reveal how a
single precursor can give rise to very distinct polymers that range from
coordination and covalent non planar polymer chains of distinct chirality, to
atomically precise graphene nanoribbons and nanoporous graphene. Our precursor
consists on adding two phenyl substituents to 10,10'-dibromo 9,9'-bianthracene,
a well-studied precursor in the on-surface synthesis of graphene nanoribbons.
The critical role of the monomer design on the reaction paths is inferred from
the fact that the phenyl substitution leads to very distinct products in each
one of the studied metallic substrates.
