A transient thermal imaging technique is used to monitor heat diffusion at the surface of the antiferromagnetic spin ladder material Ca 9 La 5 Cu 24 O 41. This material shows highly anisotropic thermal conductivity due to a large uni-directional magnetic heat transport along the ladders. The thermal conductivity is measured using optical heating as well as electrical heating, yielding 37 ± 3 W m À1 K À1 for the fast (ladder) direction and 2.5 ± 0.5 W m À1 K À1 for the slow direction, respectively. The fast direction result is in agreement with the thermal conductivity measured using other dynamic methods, but about 60% lower than the thermal conductivity measured using steady state methods.

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The reaction of 2,5-bis[N,N'-bis(2-pyridyl-aminomethyl)aminomethyl]-p-hydroquinone (H2bpymah) with VO(2+) salts in acetonitrile or water at a low pH (2.2-3.5) results in the isolation of [{V(IV)(O)(Cl)}2(μ-bpymah)], the p-semiquinonate complex [{V(IV)(O)(Cl)}2(μ-bpymas)](OH), the cyclic mixed-valent hexanuclear compound [{V(V)(O)(μ-O)V(IV)(O)}(μ-bpymah)]3, and [(V(V)O2)2(μ-bpymah)]. [{V(IV)(O)(Cl)}2(μ-bpymas)](OH) is an intermediate of the radical-mediated oxidation of [{V(IV)(O)(Cl)}2(μ-bpymah)] from O2. At lower pH values (2.2), a reversible intramolecular electron transfer from the metal to the ligand of [{V(IV)(O)(Cl)}2(μ-bpymas)](OH) is induced with the concurrent substitution of chlorine atoms by the oxygen-bridging atoms, resulting in the formation of [{V(V)(O)(μ-O)V(IV)(O)}(μ-bpymah)]3. The metal complexes were fully characterized by X-ray crystallography, infrared (IR) spectroscopy, and magnetic measurements in the solid state, as well as by conductivity measurements, UV-vis spectroscopy, and electrochemical measurements in solution. The oxidation states of the metal ions and ligands were determined by the crystallographic data. The [{V(IV)(O)(Cl)}2(μ-bpymah)]-[{V(IV)(O)(Cl)}2(μ-bpymas)](OH) redox process is electrochemically reversible. The V(IV) ion in the semiquinonate compound exhibits a surprisingly low oxophilicity, resulting in the stabilization of OH(-) counterions at acidic pH values. An investigation of the mechanism of this reaction reveals that these complexes induce the reduction of O2 to H2O2, mimicking the activity of enzymes incorporating two redox-active centers (metal-organic) in the active site.

The current transport and thermoelectric properties of Fe 3 O 4 / SiO 2 / p-type Si (001) heterostructures with Fe 3 O 4 thicknesses of 150, 200, and 350 nm have been investigated between 100 and 300 K. We observe a sharp drop of the in-plane resistivity at 200K due to the onset of conduction along the Si / SiO 2 interface related to tunneling of electrons from the Fe 3 O 4 into the accumulation layer of holes at the Si / SiO 2 interface, whose existence was confirmed by capacitance-voltage measurements and a two band analysis of the Hall effect. This is accompanied by a large increase of the Seebeck coefficient reaching +1000 μV/K at 300K that is related to holes in the p-type Si(001) and gives a power factor of 70 mW/K 2 m when the Fe 3 O 4 layer thickness is reduced down to 150 nm. We show that most of the current flows in the Fe 3 O 4 layer at 300 K, while the Fe 3 O 4 / SiO 2 / p-type Si(001) heterostructures behave like tunneling p-n junctions in the transverse direction.

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