Making closed-shell lead phthalocyanine paramagnetic on Pb(100)

Lead phthalocyanine (PbPc), a nonplanar molecule, is studied on Pb(100) by scanning tunneling spectroscopy. A rigid shift of the molecular orbitals is found between molecules with the central Pb ion pointing toward $(\mathrm{PbPc}\ensuremath{\downarrow})$ or away from $(\mathrm{PbPc}\ensuremath{\uparrow})$ the substrate and is understood from the interaction between the molecules and their image charges. Within the superconducting energy gap, Yu-Shiba-Rusinov (YSR) resonances are observed for $\mathrm{PbPc}\ensuremath{\uparrow}$ molecules in islands, indicating the presence of a magnetic moment. Such bound states are not present on $\mathrm{PbPc}\ensuremath{\downarrow}$ molecules, nor on isolated $\mathrm{PbPc}\ensuremath{\uparrow}$ or molecules that have lost the Pb ion during deposition $({\mathrm{H}}₀\mathrm{Pc})$. The YSR energies vary depending on the orientation and type of the molecular neighbors. We analyze the role of the out-of-plane electrostatic dipole moment of PbPc.