Properties and electronic structure of tetrahalogenocuprate (II)-complexes

Several salts containing the complex anions [CuCl ₄]= or [CuBr ₄]= have heen prepared, and their spectra have been measured and interpreted in terms of ligand-field theory. They exhibit a d-d band with about 8–9000 cm^–1, and several well defined charge-transfer bands in the visible and near ultraviolet spectral range. Several experimental facts, supported by theoretical considerations, indicate that the structure of the [CuX ₄]= anions is not a truly tetrahedral, but a flattened tetrahedral one, of symmetry D _2d . Details on the course of the endothermic solvolysis reactions which occur in polar organic solvents, and on the probable nature of the solvolysis products are reported and discussed.

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Zusammenfassung Mehrere Salze der komplexen Anionen [CuCl ₄]^2– und [CuBr ₄]^2– wurden dargestellt, ihre Spektren gemessen und ligandenfeldtheoretisch interpretiert. Die Spektren zeigen eine d d-Bande mit im Gebiet von 8000 bis 9000 cm^–1 und mehrere wohldefinierte Elektronenüberführungsbanden im sichtbaren und nahen ultravioletten Spektralbereich. Mehrere experimentelle Befunde, die von theoretischen Überlegungen unterstützt werden, deuten darauf hin, daß die [CuX ₄]^2/s--Anionen nicht rein tetraedrisch gebaut sind, sondern längs einer zweizähligen Achse gestauchte Tetraeder der Symmetrie D _2d darstellen.Einzelheiten über den Verlauf der endothermen Solvolysereaktionen in polaren organischen Lösungsmitteln und über die wahrscheinlichen Solvolyseprodukte werden mitgeteilt und diskutiert.

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Résumé Plusieurs sels des anions complexes [CuCl ₄]^2– et [CuBr ₄]^2– ont été préparés et leurs spectres mesurés et interprétés dans le cadre de la théorie du champ des ligands.Ils montrent une bande d d avec dans la région de 8000 à 9000 cm^–1 et plusieurs bandes bien définies du type «transfer de charges» dans le visible et l'ultraviolet proche. Plusieurs résultats expérimentaux, soutenus par des considérations théoriques, indiquent que la structure des ions [CuX ₄]^2– n'est pas celle d'un tétraèdre véritable mais celle d'un tétraèdre déformé, de symétrie D _2d , Des détails sur le cours des réactions endothermiques de solvolyse, qui ont lieu dans les solvants organiques polaires et sur la nature probable des produits de la solvolyse sont rapportés et discutés.

     

Correlation between molecular orbitals and doping dependence of the electrical conductivity in electron-doped metal-phthalocyanine compounds

We have performed a comparative study of the electronic properties of six different electron-doped metal-phthalocyanine (MPc) compounds (ZnPc, CuPc, NiPc, CoPc, FePc, and MnPc), in which the electron density is controlled by means of potassium intercalation. Despite the complexity of these systems, we find that the nature of the underlying molecular orbitals produces observable effects in the doping dependence of the electrical conductivity of the materials. For all the MPc's in which the added electrons are expected to occupy orbitals centered on the ligands (ZnPc, CuPc, and NiPc), the doping dependence of the conductivity has an essentially identical shape. This shape is different from that observed in MPc materials in which electrons are also added to orbitals centered on the metal atom (CoPc, FePc, and MnPc). The observed relation between the macroscopic electronic properties of the MPc compounds and the properties of the molecular orbitals of the constituent molecules clearly indicates the richness of the alkali-doped metal-phthalocyanines as a model class of compounds for the investigation of the electronic properties of molecular systems.     

Manifestations of phase-coherent transport in graphene

The electronic transport properties of graphene exhibit pronounced differences from those of conventional two dimensional electron systems investigated in the past. As a consequence, well established phenomena such as the integer quantum Hall effect and weak localization manifest themselves differently in graphene. Here we present an overview of recent experiments that we have performed to probe phase coherent transport. In particular, we have investigated in great detail Josephson supercurrent and superconducting proximity effect in junctions consisting of a graphene layer in between superconducting electrodes. We have also used the same devices to measure aperiodic conductance fluctuations and weak localization. The experimental results clearly indicate that low-temperature transport in graphene is phase coherent on a ∼ 1μm length scale, irrespective of the position of the Fermi level. We discuss the different behavior of Josephson supercurrent and weak localization in terms of the unusual properties of the electronic states in graphene upon time reversal symmetry.     

Ueber Untersuchung von Jodoform und Jod enthaltenden Verbandstoffen und Arzneimitteln

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