Surface Supramolecular Organization of a Terbium(III) Double-Decker Complex on Graphite and its Single Molecule Magnet Behavior

Abstract

The two-dimensional self-assembly of a terbium(III) double-decker phthalocyanine on highly oriented pyrolitic graphite (HOPG) was studied by atomic force microscopy (AFM), and it was shown that it forms highly regular rectangular two-dimensional nanocrystals on the surface, that are aligned with the graphite symmetry axes, in which the molecules are organized in a rectangular lattice as shown by scanning tunneling microscopy. Molecular dynamics simulations were run in order to model the behavior of a collection of the double-decker complexes on HOPG. The results were in excellent agreement with the experiment, showing that-after diffusion on the graphite surface-the molecules self-assemble into nanoscopic islands which align preferentially along the three main graphite axes. These low dimension assemblies of independent magnetic centers are only one molecule thick (as shown by AFM) and are therefore very interesting nanoscopic magnetic objects, in which all of the molecules are in interaction with the graphite substrate and might therefore be affected by it. The magnetic properties of these self-assembled bar-shaped islands on HOPG were studied by X-ray magnetic circular dichroism, confirming that the compounds maintain their properties as single-molecule magnets when they are in close interaction with the graphite surface.

Radical ligand-containing single-molecule magnets

“…For instance, variations of TbPc 2 have been deposited onto pyrolytic graphite [234][235][236], graphene [237,238], carbon nanotubes [239], copper (1 0 0) [240], copper (1 1 1) [241], ferro-magnetic films [242], gold films [243], gold (1 1 1) [244,245]. Interactions of TbPc 2 with single-walled nanotubes (SWNTs) [239,246], within the context of potential molecular spintronic devices have further been reported [247,248].…”

Reduction of Mn19 Coordination Clusters on a Gold Surface

“…XAS and XMCD are receiving growing interest because they allow the investigation of the magnetic properties of submonolayers of magnetic atoms and molecules on surfaces with elemental selectivity. 7,10,17,34,37,38 Whereas XAS gives information about oxidation states and ligand field, XMCD is sensitive to the magnetic moment localized at the element under investigation.…”

X-ray induced demagnetization of single-molecule magnets

“…There is growing interest in x-ray magnetic circular dichroism (XMCD) to study SMMs because of its ability to detect element-resolved magnetic moments combined with submonolayer sensitivity. [9][10][11][12][13][14] XMCD has been used to observe magnetic hysteresis, i.e., nonequilibrium magnetization in SMMs. [11][12][13] Here, we demonstrate that in endohedral SMMs the x-ray exposure itself can lead to an acceleration of magnetization relaxation.…”

“…[9][10][11][12][13][14] XMCD has been used to observe magnetic hysteresis, i.e., nonequilibrium magnetization in SMMs. [11][12][13] Here, we demonstrate that in endohedral SMMs the x-ray exposure itself can lead to an acceleration of magnetization relaxation. The x-ray induced demagnetization can be understood by the creation of small volumes of excited, or hot, molecules by the secondary electrons emitted from the Auger decay of the x-ray induced core hole.…”