Ammonium Pertechnetate in Mixtures of Trifluoromethanesulfonic Acid and Trifluoromethanesulfonic Anhydride

Ammonium pertechnetate reacts in mixtures of trifluoromethanesulfonic anhydride and trifluoromethanesulfonic acid under final formation of ammonium pentakis(trifluoromethanesulfonato)oxidotechnetate(V), (NH4)(2)[TcO(OTf)(5)]. The reaction proceeds only at exact concentrations and under the exclusion of air and moisture via pertechnetyl trifluoromethanesulfonate, [TcO3(OTf)], and intermediate Tc-VI species. Tc-99 nuclear magnetic resonance (NMR) has been used to study the Tc-VII compound and electron paramagnetic resonance (EPR), Tc-99 NMR and X-ray absorption near-edge structure (XANES) experiments indicate the presence of the reduced technetium species. In moist air, (NH4)(2)[TcO(OTf)(5)] slowly hydrolyses under formation of the tetrameric oxidotechnetate(V) (NH4)(4)[{TcO(TcO4)(4)}(4)] .10 H2O. Single-crystal X-ray crystallography was used to determine the solid-state structures. Additionally, UV/Vis absorption and IR spectra as well as quantum chemical calculations confirm the identity of the species

UoC-3: A Metal-Organic Framework with an Anionic Framework Based on Uranyl UO22+ Nodes and Partly Fluorinated Benzene-1,3,5-Tribenzoate Linkers

The reaction of UO2(NO3) 2 center dot 6H(2)O with partly fluorinated H-3-3F-BTB (BTB3-: benzene- 1,3,5-tribenzoate) in N,N-dimethylformamide (DMF) leads to the crystallization of the metal-organic framework (MOF) [(CH3)(2)NH2][UO2(3F-BTB)]center dot xDMF, named UoC-3 (UoC: University of Cologne). X-ray singlecrystal structure analysis (Pnna, Z = 4) reveals that an anionic framework is formed, in which UO22+ nodes are connected by 3F-BTB3- ligands. Because of the fluorination of the inner ring of the linker, its three benzoate groups are tilted to an out of plane arrangement, which leads to the formation of a three-dimensional structure with large pores. This is in contrast to a known uranyl coordination polymer with the unfluorinated BTB3- linker, where an almost coplanar arrangement of the linker leads to graphene-like layers. The high porosity of UoC-3 was confirmed by N-2 gas sorption measurements, resulting in SBET = 4844 m(2)/g. The charge compensating [(CH3)(2)NH2](+) cation is formed by hydrolysis of DMF. Direct addition of [(CH3)(2)NH2]Cl to the reaction carried out in ethanol/H2O (v:v, 5:1) leads to the same MOF but with lower crystallinity. When using solvents, which hydrolyze to larger cations (e.g., N,N-diethylformamide (DEF): [(C2H5)2NH(2)](+) and N,N-di(n-butyl)formamide (DBF): [(C4H9)(2)NH2](+)), again the formation of UoC-3 was found, as confirmed by X-ray single-crystal analysis and X-ray powder diffraction. Thus, no templating effect was achieved with these cations. The exchange of the organic cations by K+ turned out to be successful, as revealed by XPS analysis. UoC-3 was also successfully tested to remove approximately 96% radioactive Cs-137(+) from aqueous solutions (93% after one regeneration cycle) while retaining its crystal structure

Characterization of Remote Sensing Albedo Over Sloped Surfaces Based on DART Simulations and In Situ Observations

International audienceAbstract In situ albedo measurement over sloped surfaces is pivotal to a wide range of remote sensing applications, such as the estimation and evaluation of surface energy budget at regional and global scales. However, existing albedo measurements over rugged terrain are limited and controversial and remain a major challenge. In this paper, two commonly measured broadband albedos, which depend on incoming/outgoing geometric conditions, were characterized over sloped surfaces and illustrated. These albedos are the horizontal/horizontal sloped surface albedo (HHSA) and inclined/inclined sloped surface albedo (IISA). The 3‐D Discrete Anisotropic Radiative Transfer (DART) model simulations over varying slopes were utilized to quantify differences in the albedos. In particular, the effects of the slope, aspect, the solar zenith angle, and the proportion of diffuse skylight were investigated. The results show that absolute (relative) biases between HHSA and IISA are significant, reaching up to 0.026 (61.8%), 0.134 (62.4%), and 0.114 (62.3%) in the visible, near‐infrared, and shortwave broadbands, respectively. In addition, the diurnal cycle differences between HHSA and IISA were also compared using DART simulations and in situ observations over four typical slopes. Comparisons reveal that topographic parameters (e.g., slope and aspect) and atmospheric conditions (e.g., diffuse skylight and atmospheric visibility) are the primary factors, while the optical and structural parameters have a smaller effect