Structural Transformation of Surface‐Confined Porphyrin Networks by Addition of Co Atoms

The self‐assembly of a nickel‐porphyrin derivative (Ni‐DPPyP) containing two pyridyl coordinating sites and two pentyl chains at trans meso positions was studied with scanning tunneling microscopy (STM), X‐ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) on Au(111). Deposition of Ni‐DPPyP onto Au(111) gave rise to a close‐packed network for coverages smaller or equal to one monolayer as revealed by STM and LEED. The molecular arrangement of this two‐dimensional network is stabilized via hydrogen bonds formed between the pyridyl's nitrogen and hydrogen atoms from the pyrrole groups of neighboring molecules. Subsequent deposition of cobalt atoms onto the close‐packed network and post‐deposition annealing at 423 K led to the formation of a Co‐coordinated hexagonal porous network. As confirmed by XPS measurements, the porous network is stabilized by metal‐ligand interactions between one cobalt atom and three pyridyl ligands, each pyridyl ligand coming from a different Ni‐DPPyP molecule. The structural transformation of a porphyrin‐based two‐dimensional network from its H‐bonded phase to a porous metal‐coordinated phase after the addition of Co‐atoms on Au(111) under ultra‐high vacuum conditions was inverstigated. The networks were characterized by scanning tunneling microscopy, low‐energy electron diffraction and X‐ray photoelectron spectroscopy.