On-Surface Molecular Design and Synthesis of Discrete Metal–Fullerene Complexes on Graphite

Abstract On-surface synthesis enables the fabrication of molecular complexes, which cannot be obtained through traditional solution chemistry. Generally, metal substrates have been used due to their catalytic properties. Here, a tripod-like magnetic molecular complex, (C60)3–Co, has been created on an inert nonmetal substrate, graphite, and characterized with the scanning tunneling microscopy through on-surface synthesis. By deposition of Co atoms onto a double layer of C60 supported on a graphite substrate, the Co atoms get trapped within the room temperature C60 layers before the formation of (C60)3–Co via a totally self-organized reaction at 543 K. The reaction has a selectivity of 62% toward (C60)3–Co. The azimuthal orientation of the (C60)3–Co complex approaches 100%. The fullerene–cobalt complex, featuring a planar equilateral triangular structure with sides measuring 1 nm, stands on the graphite support using the three C60 legs. The magnetic Co forms three identical chemical bonds to C60 molecules, and it is effectively decoupled from the substrate. The (C60)3–Co complex carries a magnetic moment of the order of 1 μB according to DFT calculations. Our work extends the synthetic pathway to involve inert nonmetal substrates and offers an extra advantage that the synthesized structure maintains its intrinsic properties due to the lack of a screening effect from a metallic substrate. Furthermore, an inert substrate functions as a physical support without actively participating in the synthesis process itself, and hence the synthetic reaction is primarily governed by interactions among the reactants.