The Kondo Effect of a Molecular Tip As a Magnetic Sensor.

A single molecule offers to tailor and control the probing capability of a scanning tunneling microscope when placed on the tip. With the help of first-principles calculations, we show that on-tip spin sensitivity is possible through the Kondo ground state of a spin = 1/2 cobaltocene molecule. When attached to the tip apex, we observe a reproducible Kondo resonance, which splits apart upon tuning the exchange coupling of cobaltocene to an iron atom on the surface.

Enhancing Hydrogen Evolution Activity of Au(111) in Alkaline Media through Molecular Engineering of a 2D Polymer.

The electrochemical splitting of water holds promise for the storage of energy produced intermittently by renewable energy sources. The evolution of hydrogen currently relies on the use of platinum as a catalyst-which is scarce and expensive-and ongoing research is focused towards finding cheaper alternatives. In this context, 2D polymers grown as single layers on surfaces have emerged as porous materials with tunable chemical and electronic structures that can be used for improving the catalytic activity of metal surfaces.

Implementing Functionality in Molecular Self-Assembled Monolayers.

The planar heterocyclic molecules 1,6,7,12-tetraazaperylene on a Ag(111) metal substrate show different charging characteristics depending on their local environment: next to vacancies in self-assembled islands, molecules can be charged by local electric fields, whereas their charge state is fixed otherwise. This enables the activation of selected molecules inside islands by vacancy creation from scanning-probe-based manipulation. This concept allows for combining the precise mutual atomic-scale alignment of molecules by self-assembly, on one hand, and the implementation of specific functionality into otherwise homogeneous monolayers, on the other.

On-surface transmetalation of metalloporphyrins.

Increasing the complexity of 2D metal-organic networks has led to the fabrication of structures with interesting magnetic and catalytic properties. However, increasing complexity by providing different coordination environments for different metal types imposes limitations on their synthesis if the controlled placement of one metal type into one coordination environment is desired. Whereas metal insertion into free-base porphyrins at the vacuum/solid interface has been thoroughly studied, providing detailed insight into the mechanisms at play, the chemical interaction of a metal atom with a metallated porphyrin is rarely investigated.

On-surface synthesis of heptacene on Ag(001) from brominated and non-brominated tetrahydroheptacene precursors.

Achieving the Ag(001)-supported synthesis of heptacene from two related reactants reveals the effect of the presence of Br atoms on the reaction process. The properties of reactants, intermediates and end-products are further characterized by scanning tunneling microscopy and spectroscopy.

Efficient Spin-Flip Excitation of a Nickelocene Molecule.

Inelastic electron tunneling spectroscopy (IETS) within the junction of a scanning tunneling microscope (STM) uses current-driven spin-flip excitations for an all-electrical characterization of the spin state of a single object. Usually decoupling layers between the single object, atom or molecule, and the supporting surface are needed to observe these excitations. Here we study the surface magnetism of a sandwich nickelocene molecule (Nc) adsorbed directly on Cu(100) by means of X-ray magnetic circular dichroism (XMCD) and density functional theory (DFT) calculations and show with IETS that it exhibits an exceptionally efficient spin-flip excitation.

AFM Imaging of Mercaptobenzoic Acid on Au(110): Submolecular Contrast with Metal Tips.

A self-assembled monolayer of mercaptobenzoic acid (MBA) on Au(110) is investigated with scanning tunneling and atomic force microscopy (STM and AFM) and density functional calculations. High-resolution AFM images obtained with metallic tips show clear contrasts between oxygen atoms and phenyl moieties. The contrast above the oxygen atoms is due to attractive covalent interactions, which is different than previously reported high-resolution images, where Pauli repulsion dominated the image contrast.

On-Surface Engineering of a Magnetic Organometallic Nanowire.

The manipulation of the molecular spin state by atom doping is an attractive strategy to confer desirable magnetic properties to molecules. Here, we present the formation of novel magnetic metallocenes by following this approach. In particular, two different on-surface procedures to build isolated and layer-integrated Co-ferrocene (CoFc) molecules on a metallic substrate via atomic manipulation and atom deposition are shown.

Assembly of Ferrocene Molecules on Metal Surfaces Revisited.

Metallocene (MCp2) wires have recently attracted considerable interest in relation to molecular spintronics due to predictions concerning their half-metallic nature. This exciting prospect is however hampered by the little and often-contradictory knowledge we have concerning the metallocene self-assembly and interaction with a metal. Here, we elucidate these aspects by focusing on the adsorption of ferrocene on Cu(111) and Cu(100).