STM/STS Observation of Polyoxoanions on HOPG Surfaces:  the Wheel-Shaped [Cu₂₀Cl(OH)₂₄(H₂O)₁₂(P₈W₄₈O₁₈₄)]^25- and the Ball-Shaped [{Sn(CH₃)₂(H₂O)}₂₄{Sn(CH₃)₂}₁₂(A-PW₉O₃₄)₁₂]^36-

Abstract

A combination of scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) techniques have been performed on the wheel-shaped [Cu20Cl(OH)24(H2O)12(P8W48O184)]25- and the ball-shaped [{Sn(CH3)2(H2O)}24{Sn(CH3)2}12(A-PW9O34)12]36- deposited on highly oriented pyrolytic graphite surfaces. Small, regular molecule clusters, as well as separated single molecules, were observed. The size of the molecules is in agreement with the data determined by X-ray crystallography. In STS measurements, we found a rather large contrast at the expected location of the Cu metal centers in our molecules, i.e., the location of the individual Cu ions in their organic matrix is directly addressable by STS.

Oligonuclear Fe Complexes (Fe, Fe4, Fe6, Fe9) Derived from Tritopic Pyridine Bis-Hydrazone Ligands—Structural, Magnetic, and Mössbauer Studies

“…Grid core dimensions obtained by this method closely match those revealed by single crystal structural methods, even to the details of the canted sideways orientation of the grid on the surface. Similar observations have recently been made with a Co(II) 4 [2 × 2] square grid system, 17 a Cu(II) 20 wheel shaped polyanion, 18 and a Fe(III) 4 star shaped cluster. 19 The importance of these techniques for addressing and probing metal centers in supramolecular assemblies applied to surfaces is discussed in more detail in a review article.…”

Spinzustandsmuster in oberflächenfixierten “Perlenschnüren” aus Eisen(II)‐Komplexen

“…B. current-imaging tunneling spectroscopy, CITS), [18] erlaubt uns, elektronische Zustände der Moleküle in Abhängigkeit von der Energie innerhalb einiger Elektronenvolt (eV) um das Fermi-Niveau zu untersuchen. [19][20][21][22][23] Im Allgemeinen liefern CITS-Messungen direkte Informationen über die lokale Leitfähigkeit bei diesen Energien.…”

Immobilization of Polyoxometalates on Tailored Polymeric Surfaces

“…For example, the anchorage of a given POM to a solid substrate can lead to the combination of its catalytic activity in homogeneous phase with the ease of recovery and recycling shown by heterogeneous catalysts, which represents a clear demand for industrial purposes [35,36]. Different solid substrates have been employed as POM supports, such as oxides (alumina, silica), metals (silicon, gold), and HOPG [37,38,39,40,41,42,43]. Since POMs are negatively charged, their immobilization usually relies on electrostatic interactions, which might result in partial leaching of these clusters.…”