Rastertunnelmikroskopie wurde zur Detektion von individuellen Einzelmolekülmagneten auf Goldsubstraten eingesetzt (siehe schematische Formel). Das Adsorbat, [Mn12O12(L)16(H2O)4], wurde durch Abscheidung eines abgeschirmten Dodecamangan(III,IV)‐Clusters aus verdünnten Lösungen in THF/H2O/NH4OH erhalten. Das System kann als erste Stufe hin zu Informationsspeichern mit ultrahoher Speicherdichte auf der Grundlage von Einzelmolekülmagneten angesehen werden.

Background: During the last years engineered nanoparticles (NPs) have been extensively used in different technologies and consequently many questions have arisen about the risk and the impact on human health following exposure to nanoparticles. Nevertheless, at present knowledge about the cytotoxicity induced by NPs is still largely incomplete. In this context, we have investigated the cytotoxicity induced by gold nanoparticles (AuNPs), which differed in size and purification grade (presence or absence of sodium citrate residues on the particle surface) in vitro, in the human alveolar type-II (ATII)-like cell lines A549 and NCIH441.

The incorporation of thioether groups in the structure of a Mn12 single-molecule magnet, [Mn12(O12)(L)16(H2O)4] with L = 4-(methylthio)benzoate, is a successful route to the deposition of well-separated clusters on native gold surfaces and to the addressing of individual molecules by scanning tunnelling microscopy.

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Monodisperse and stable cobalt ferrite (CoFe2O4) nanoparticles (5.4 nm) have been produced, coated with mono- and difunctional phosphonic and hydroxamic acids, and fully characterized (using thermogravimetric analysis (TGA), dynamic light scattering (DLS), IR spectroscopy, transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID) measurements). Cobalt leakage of the coated nanoparticles has been also studied. Magnetic measurements show the possible applications in hyperthermia at low frequencies, and for this reason, water-soluble coated CoFe2O4 can be seen as a first step toward the obtainment of novel systems for biomagnetic applications.

The tailoring of the structure and properties of singlemolecule magnets (SMMs) is a very active branch of modern coordination chemistry. Investigations on classes of structurally related SMMs, such as those of the Mn 12 family, have helped unravel the mechanisms underlying slow magnetic relaxation in high-spin molecules, a key step in both fundamental and application-oriented research.[1] At the same time, the search for new SMMs with higher blocking temperatures has fueled synthetic efforts aimed, on one side, at increasing structural control on cluster architectures [2] and, on the other side, at developing the so-called serendipitousassembly approach.[3] An elegant strategy for structural design is based on site-specific modification of preformed clusters.[4] Carboxylate abstraction from Mn 12 clusters, for instance, has been carried out site specifically using a variety of incoming ligands, such as nitrates, [4a] phosphanates, [4b] phosphates, [4c] or different carboxylates.[4d] However, these substitutions are accompanied by only small perturbation of the magnetic properties.The SMM behavior is associated with the magnetic anisotropy of clusters, which in turn depends on local anisotropies and on the way they vectorially add to give a resulting total anisotropy.[5a] Herein we show that site-specific ligand replacement provides a means to raise the symmetry of Fe 4 clusters from C 2 to D 3 , which results in a dramatic increase of magnetic anisotropy and energy barrier. Fe 4 clusters are among the simplest inorganic systems showing SMM behavior. [5,6] The archetypal member of this class is the tetrairon(iii) compound [Fe 4 (OMe) 6 (dpm) 6 ] (1) (Hdpm = dipivaloylmethane). The six m-methoxide ligands bridge a central iron(iii) ion to three peripheral iron centers arranged at the vertices of an isosceles triangle [5a] with a crystallographic C 2 symmetry, and some disorder which yields three different isomers in the lattice. At low temperature, the cluster has a high-spin state (S = 5) and an easy-axis magnetic anisotropy, two requisites for the observation of slow magnetic relaxation. For the major component, the second-order zero-field splitting (ZFS) parameters are D = À0.206(1) cm À1 and E = 0.010(3) cm À1 . In addition, the presence of sizeable fourth-order contributions has been demonstrated.[5b]

A new technique to produce very small magnetic nanoparticles of maghemite (γ-Fe2O3) is presented. The particles form and precipitate in the presence of the oligosaccharide γ-cyclodextrin and in the final product remain entrapped in tiny pseudo-single crystals of the organic host. Evidence of nanosized particles embedded in the organic crystal was obtained by HR-TEM studies that showed the occurrence of uniformly dispersed particles with average diameter of 18 Å. The resulting objects gave diffraction patterns with the same spacing as that of cyclodextrin crystals without iron. The magnetic properties were investigated by ZFC−FC magnetizations, hysteresis loops, and ac susceptibility measurements. The compound presents a complex magnetic behavior that deviates from that predicted on the basis of the classic single domain particle model. The deviation is ascribed to the complex properties of the surface, which, for such small sizes, plays the major role in determining the total magnetic behavior.

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