The interaction of molecules with surfaces plays a crucial role in the electronic and chemical properties of supported molecules and needs a comprehensive description of interfacial effects. Here, we unveil the effect of the substrate on the electronic configuration of iron porphyrin molecules on Au(111) and graphene, and we provide a physical picture of the molecule-surface interaction. We show that the frontier orbitals derive from different electronic states depending on the substrate. The origin of this difference comes from molecule-substrate orbital selective coupling caused by reduced symmetry and interaction with the substrate. The weak interaction on graphene keeps

Incorporating functional atomic sites in graphene is essential for realizing advanced two-dimensional materials. Doping graphene with nitrogen offers the opportunity to tune its chemical activity, with significant charge redistribution occurring between molecules and substrate. The necessary atomic scale understanding of how this depends on the spatial distribution of dopants, as well as their positions relative to the molecule, can be provided by scanning tunneling microscopy. Here we show that a non-covalently bonded molecule such as CoPc undergoes a variable charge transfer when placed on N-doped graphene: on a nitrogen pair, it undergoes a redox reaction, with an integral charge transfer, whereas a lower fractional charge transfer occurs over a single nitrogen.Thus the charge state of molecules can be tuned by suitably tailoring the conformation of dopant atoms.

Controlling the spatial distribution of dopants in graphene is the gateway to the realization of graphene-based electronic components. Here, it is shown that a submonolayer of self-assembled physisorbed molecules can be used as a resist during a post-synthesis nitrogen doping process to realize a nanopatterning of nitrogen dopants in graphene. The resulting formation of domains with different nitrogen concentrations allows obtaining n-n' and p-n junctions in graphene. A scanning tunneling microscopy is used to measure the electronic properties of the junctions at the atomic scale and reveal their intrinsic width that is found to be ≈7 nm corresponding to a sharp junction regime.