  Graphene - transition metal phthalocyanine (G-MPc) hybrid systems constitute
promising platforms for densely-packed single-molecule magnets (SMMs). Here, we
selected iron(II) phthalocyanine (FePc) and investigated its interaction with
pristine and defective graphene layers employing density functional theory. Our
calculations indicate that thorough proper dehydrogenation of the benzol rings
in the FePc molecule its adsorption to graphene is thermodynamically favorable.
In general, the presence of anchoring sites on the graphene layer, i.e. point
defects, additionally facilitates the adsorption of FePc, allowing one to
achieve high density of SMMs per unit area. Using the combination of group
theory, ligand field splitting, and the calculated PBE0 Kohn-Sham eigenvalue
spectrum, we resolved the electronic structure and predicted the spin states of
both, the isolated FePc and G-FePc hybrid systems. Regardless of adsorption
site and the number of removed hydrogen atoms from the benzol rings of FePc,
the magnetic moment of the SMM remains unchanged with respect to free FePc.
These results should mediate a successful synthesis of densely-packed G-MPc
systems and may open up new avenue in designing scalable graphene - SMMs
systems for spintronics applications.
