Metal-organic coordination networks (MOCNs) have attracted wide interest because they provide a novel route towards porous materials that may find applications in molecular recognition, catalysis, gas storage and separation. The so-called rational design principle-synthesis of materials with predictable structures and properties-has been explored using appropriate organic molecular linkers connecting to metal nodes to control pore size and functionality of open coordination networks. Here we demonstrate the fabrication of surface-supported MOCNs comprising tailored pore sizes and chemical functionality by the modular assembly of polytopic organic carboxylate linker molecules and iron atoms on a Cu(100) surface under ultra-high-vacuum conditions. These arrays provide versatile templates for the handling and organization of functional species at the nanoscale, as is demonstrated by their use to accommodate C(60) guest molecules. Temperature-controlled studies reveal, at the single-molecule level, how pore size and chemical functionality determine the host-guest interactions.

Designing systems with large magnetic anisotropy is critical to realize nanoscopic magnets. Thus far, the magnetic anisotropy energy per atom in single-molecule magnets and ferromagnetic films remains typically one to two orders of magnitude below the theoretical limit imposed by the atomic spin-orbit interaction. We realized the maximum magnetic anisotropy for a 3d transition metal atom by coordinating a single Co atom to the O site of an MgO(100) surface. Scanning tunneling spectroscopy reveals a record-high zero-field splitting of 58 millielectron volts as well as slow relaxation of the Co atom's magnetization. This striking behavior originates from the dominating axial ligand field at the O adsorption site, which leads to out-of-plane uniaxial anisotropy while preserving the gas-phase orbital moment of Co, as observed with x-ray magnetic circular dichroism.

A permanent magnet retains a substantial fraction of its saturation magnetization in the absence of an external magnetic field. Realizing magnetic remanence in a single atom allows for storing and processing information in the smallest unit of matter. We show that individual holmium (Ho) atoms adsorbed on ultrathin MgO(100) layers on Ag(100) exhibit magnetic remanence up to a temperature of 30 kelvin and a relaxation time of 1500 seconds at 10 kelvin. This extraordinary stability is achieved by the realization of a symmetry-protected magnetic ground state and by decoupling the Ho spin from the underlying metal by a tunnel barrier.

. The control of magnetic anisotropy is a key issue in the development of molecule-metal interfaces for magnetic applications, both at the single-molecule 12 and extended-film level 13 . In metallic multilayers used as storage media or spin-valve devices at present, tuning of the magnetic anisotropy is achieved either by a careful choice of the overlayer/substrate composition and thickness or by oxidation of the magnetic elements 11,14,15 . Recent studies showed that the magnetization direction of surface-supported paramagnetic molecules can be controlled through exchange coupling with a magnetic film, which provides robust ferromagnetic properties but does not enable each molecule to be switched independently from the substrate or its neighbours 16,17 . Alternatively, theoretical work suggested that the sign of magnetic anisotropy could be reversed in metal-organic complexes by exploiting oxidation processes that affect the hybridization of molecular orbitals with metal states carrying non-zero orbital magnetization 18 . Here, we investigate supramolecular self-assembly on a non-magnetic Cu surface as a means to produce two-dimensional