Mixed-valence behavior and strong correlation effects of metal phthalocyanines adsorbed on metals

Abstract

We investigate the hierarchy of local correlation and hybridization effects in metal-organic molecules adsorbed on metals. Using x-ray magnetic circular dichroism and ligand field multiplet calculations, we demonstrate that the 3$d$ electronic ground state of monolayer metal-phthalocyanine (CoPc, FePc) on Au(111) is given by the coherent superposition of two charge states, ${d}^{n}E+{d}^{n+1}$, where $E$ represents a substrate electron antiferromagnetically coupled to the central metal ion and ${d}^{n}$ the many-body ionic orbital configuration of the unperturbed molecule. These results differ from previous models of hybrid metal-organic systems and provide a consistent description of their magnetic moments and Kondo physics in terms of spin and orbital multiplicity.