Hierarchical Self-Assembly and Conformation of Tb Double-Decker Molecular Magnets: Experiment and Molecular Dynamics

Nanostructures, fabricated by locating molecular building blocks in well-defined positions, for example, on a lattice, are ideal platforms for studying atomic-scale quantum effects. In this context, STM data obtained from self-assembled Bis(phthalocyaninato) Terbium (III) (TbPc₂) single-molecule magnets on various substrates have raised questions about the conformation of the TbPc₂ molecules within the lattice. In order to address this issue, molecular dynamics simulations were carried out on a 2D assembly of TbPc₂ molecules. The calculations are in excellent agreement with the experiment, and thus improve our understanding of the self-assembly process. In particular, the calculated electron density of the molecular assembly compares well with STM contrast of self-assembled TbPc₂ on Au(111), simultaneously providing the conformation of the two Pc ligands of the individual double-decker molecule. This approach proves valuable in the identification of the STM contrast of LnPc₂ layers and could be used in similar cases where it is difficult to interpret the STM images of an assembly of molecular complexes.