  Hybrid sp-sp2 structures can be efficiently obtained on metal substrates via
on-surface synthesis. The choice of both the precursor and of the substrate
impacts on the effectiveness of the process and the stability of the formed
structures. Here we demonstrate that using anthracene-based molecules as
precursor, the formation on Au(111) of polymers hosting sp carbon chains is
affected by the steric hindrance between aromatic groups. In particular, by
scanning tunneling microscopy and density functional theory calculations we
show that the de-metalation of organometallic structures induces a lateral
separation of adjacent polymers preventing the formation of ordered domains.
