Uranyl oxo activation and functionalization by metal cation coordination

International audienceThe oxo groups in the uranyl ion [UO$_2$]$^{2+}$ , one of many oxo cations formed by metals from across the periodic table—are particularly inert, which explains the dominance of this ion in the laboratory and its persistence as an environmental contaminant. In contrast, transition metal oxo (M=O) compounds can be highly reactive and carry out difficult reactions such as the oxygenation of hydrocarbons. Here we show how the sequential addition of a lithium metal base to the uranyl ion constrained in a ‘Pacman’ environment results in lithium coordination to the U=O bonds and single-electron reduction. This reaction depends on the nature and stoichiometry of the lithium reagent and suggests that competing reduction and C–H bond activation reactions are occurring

Upper critical magnetic field and vortex-free state in very thin epitaxial delta-MoN films grown by polymer-assisted deposition

We measured the thickness dependence of the superconducting properties in epitaxial delta-MoN thin films grown on alpha-Al2O3(001) substrates by polymer-assisted deposition. Our results indicate that the superconducting properties such as the upper critical field (mu H-0(c2) approximate to 10 T) and the superconducting critical temperature (T-c = 12.5 K) are thickness independent for films thicker than similar to 36 nm. By measuring the critical current density (J(c)) in the vortex-free state, which coincides with the depairing current density (J(0)), we estimate that films thicker than similar to 36 nm have a coherence length xi(0) = 5.8 +/- 0.2 nm and penetration depth lambda(0) = 420 +/- 50 nm. We found that it is possible to enhance the H-c2(0) values to close to 10 T without any appreciable reduction in T-c.11118sciescopu