Guided Molecular Assembly on a Locally Reactive 2D Material

Abstract

Atomically precise engineering of the position of molecular adsorbates on surfaces of 2D materials is key to their development in applications ranging from catalysis to single-molecule spintronics. Here, stable room-temperature templating of individual molecules with localized electronic states on the surface of a locally reactive 2D material, silicene grown on ZrB₂, is demonstrated. Using a combination of scanning tunneling microscopy and density functional theory, it is shown that the binding of iron phthalocyanine (FePc) molecules is mediated via the strong chemisorption of the central Fe atom to the sp³-like dangling bond of Si atoms in the linear silicene domain boundaries. Since the planar Pc ligand couples to the Fe atom mostly through the in-plane d orbitals, localized electronic states resembling those of the free molecule can be resolved. Furthermore, rotation of the molecule is restrained because of charge rearrangement induced by the bonding. These results highlight how nanoscale changes can induce reactivity in 2D materials, which can provide unique surface interactions for enabling novel forms of guided molecular assembly.

Molecular templating using a locally reactive 2D material is achieved at the domain boundaries of silicene formed on ZrB₂. Selective bonding between silicene sp³-like states and the d_z² orbitals of iron phthalocyanine (FePc) molecules preserves electronic states that are strongly localized on the Pc ligand while pinning the molecule into a unique rotational alignment up to room temperature.

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