Probing the long-range magnetic coupling within a 2D extended transition metal-organic coordination network (2D-TMOCN) by varying the metal-to-ligand charge transfer

We propose to use self-assembled highly extended organic templates deposited on strongly interacted noble metal surfaces, such as Ag(100) and Cu(100), for the engineering of an extended metal-organic coordination network (MOCN). The interaction between molecular precursors and substrate preserves the high sample quality and, at the same time, steers the metal-organic coordination interaction with the co-adsorbed 3d transition metal (TM) atoms. However, the coupling between the molecular ligand and TM can alter or even completely quench the magnetic moment of the chelated ion, because of the interaction occurring between the 3d shell and the molecular orbitals of the ligand or/and with the metal substrate. In this context, we recently studied a metal-organic network constitued by magnetic Ni(I) and Fe(I) centers stabilized in a quadratic planar configuration by the cyano-groups of 1,2,4,5-tetracyanobenzene (TCNB) supported on the Ag(100) surface. We observed a strong XMCD signal in the case of Ni(I) while a very weak one for the Fe centers. At the same time, the valence band spectra show the presence of a new state induced by the metal-organic coordination in the LUMO and HOMO gap in the case of Ni(I) ion, while we detected an energy overlap between the LUMO and the state associated with the Fe(I) coordination; this possible hybridization between the 3d Fe states and the LUMO may cause the quenching of the magnetic moment in the Fe centers. The electron affinity of the molecular ligand and the supporting substrate can induce changes in the molecular levels in adsorbed species. Therefore, in this proposal, we would like to tune the electronic structure of the MOCN based on 3d TMs by changing the p-acceptor electron affinity in both organic ligands and substrates and, at the same time, monitor the magnetic properties of the MOCN.