Narrow Results

The synthesis and reactivity of uranium complexes supported by a bis(aryloxide) cyclam ligand are surveyed. The hemilability of this ligand proved to be particularly appropriate to stabilize highly reactive uranium(III) and uranium(IV) complexes that were able to activate different unsaturated molecules. Of note are the reductive cleavage of azobenzene with the unprecedented formation of a trans-bis(imido) uranium(VI) complex and its reaction with carbon dioxide to generate a trans-oxido-imido uranium(VI) complex and phenyl isocyanate. The formation of a trans-dioxido uranium(VI) (uranyl) complex was also observed in the reaction of uranium(IV) complexes with sodium nitrite. Quantum chemical computations and solution ¹⁵N NMR spectroscopy were employed to evaluate bond covalency in the three {E=U=E}²⁺ complexes (E = O, NR).

The structural, elastic and electronic properties of Al₃Fe, Al₆Mn and Mg₂Si have been researched by first-principles calculations within the framework of generalized gradient approximation (GGA). The structural parameters and electronic structure such as lattice constant (a₀), shear modulus (G) and density of states (DOS) are in good agreement with the theoretical and experimental results available. It can be inferred from the negative cohesive energy and formation enthalpy that these compounds are structural stable, and the Al₃Fe phase is much steady from energetic point of view. The elastic constant of these phases obtained comply with the mechanical stability conditions. Then the shear modulus G, bulk modulus B, Young’s modulus E and Poisson’s ratio v of the studied compounds were concluded. Electronic structure of these compounds has been analyzed from electron density and density of states distribution.

Heteroatomic mesoporous Ce-MCM-41 molecular sieve was synthesized by using hydrothermal synthesis method. X-ray diffraction (XRD) and Infrared spectrophotometer (IR) results indicated that the well-ordered mesostructure was obtained and Ce had been introduced into the framework of MCM-41. Nitrogen adsorption-desorption results indicated that the average pore diameters of MCM-41 and Ce-MCM-41(Ce/Si molar ratio=0.04) were 3.24 and 3.85 nm, with pore volumes of 0.4256 and 0.8721 m³/g, Brunauer-Emmett-Teller (BET) surface areas of 587.65 m²/g and 612.35 m²/g respectively. The molecular size of dimethyl sulfide, calculated by using density functional theory (DFT), was 0.4648 nm, implying that the dimethyl sulfide easy accessed to the mesoscale pores of mesoporous molecular sieve. NH₃-TPD results illustrated that the acidity of Ce-MCM-41(Ce/Si=0.04) was stronger than that of MCM-41. As a result, for the adsorptive removal of dimethyl sulfide from nitrogen with a dimethyl sulfide content of 58 μg/g (that was 30 μg (S)/g), the desulfurization capacity of Ce-MCM-41(Ce/Si=0.04) was 7.52 mg(S)/g, higher than that of MCM-41 (4.57 mg(S)/g).