Impact of the Substrate Work Function on Self-Assembling and Electronic Structure of Adsorbed Ruthenium Phthalocyanine

We report on a systematic study of bis-rutheniumphthalocyanine, (RuPc)2, layers deposited on Au(111), Ag(111), andgraphite. By scanning tunneling microscopy and density functional theorycalculations, a detailed picture of the molecular orbitals rearrangementdue to the contact with the substrate is drawn, which reveals a significantsubstrate impact on the molecule charge and spin patterns. On the metalsubstrates a reduction of the Ru-Ru dimer magnetic moment is observeddue to thefilling of a spin-down singly unoccupied molecular orbital.However, the higher work function of Au(111) induces a chargebackdonation, which results in an unexpected spin polarization of themolecule ligand. On the other hand, the contact with graphite leaves theelectronic and magnetic properties of (RuPc)2largely unaffected. The self-assembling process of the molecules on the different substrates has alsobeen thoroughly investigated and interpreted in the light of molecular orbital rearrangements. On the low interacting graphitesubstrate, the process is mainly driven by molecule-molecule interactions leading to a square structure. Conversely, on Ag(111) andAu(111), the stronger molecule-substrate interaction produces a more complex scenario characterized by a manifold of structures.