Exploration of a Unique Uranium Mediated Carbon-Carbon Radical Coupling Reaction

Designing an efficient nuclear fuel cycle has motivated decades of research on aqueous phase uranium chemistry. As such, studies are often limited by the formation of unreactive uranium oxides and/or solubility issues. Carrying out reactions in non-aqueous solvents addresses said problems and enables explorations into previously unattainable reactivity and fundamental properties of uranium. One such feat is the syntheses of uranium alkyls, as they permit research into bond interactions between uranium and carbon. Considering uranium’s oxophilicity, we investigated the relatively understudied uranium(III) alkyls—both their reactivity and reaction mechanism—towards oxygen-containing reagents. In an inert atmosphere, various uranium alkyl complexes were treated with substituted phosphine oxides, which provide electronic and steric modularity. Products were characterized via nuclear magnetic resonance (NMR), electronic absorption, and infrared spectroscopies. X-ray crystallographic data were obtained whenever possible. We observed the formation of a new carbon-carbon bond between the alkyl unit and phosphine oxide in a one-electron mechanism, while maintaining the U(III) oxidation state. This radical coupling was favored by electron-poor phosphine oxide and impeded by electron-rich analogs. The ability for the alkyl to form stable radicals drives the reaction forward. All attempts to capture the radical were unsuccessful, as the formation of the new uranium complexes appears to occur in concert with the homolytic cleavage of the U—C bond. To the best of our knowledge, such reactivity with phosphine oxides is unprecedented in the field of coordination chemistry

The mechanism of high contents of oil and oleic acid revealed by transcriptomic and lipidomic analysis during embryogenesis in Carya cathayensis Sarg.

Gene transcription in lipid synthesis. (XLSX 55 kb

Multi-Feature Based Ocean Oil Spill Detection for Polarimetric SAR Data Using Random Forest and the Self-Similarity Parameter

Synthetic aperture radar (SAR) is an important means to detect ocean oil spills which cause serious damage to the marine ecosystem. However, the look-alikes, which have a similar behavior to oil slicks in SAR images, will reduce the oil spill detection accuracy. Therefore, a novel oil spill detection method based on multiple features of polarimetric SAR data is proposed to improve the detection accuracy in this paper. In this method, the self-similarity parameter, which is sensitive to the randomness of the scattering target, is introduced to enhance the discrimination ability between oil slicks and look-alikes. The proposed method uses the Random Forest classification combing self-similarity parameter with seven well-known features to improve oil spill detection accuracy. Evaluations and comparisons were conducted with Radarsat-2 and UAVSAR polarimetric SAR datasets, which shows that: (1) the oil spill detection accuracy of the proposed method reaches 92.99% and 82.25% in two datasets, respectively, which is higher than three well-known methods. (2) Compared with other seven polarimetric features, self-similarity parameter has the better oil spill detection capability in the scene with lower wind speed close to 2⁻3 m/s, while, when the wind speed is close to 9⁻12 m/s, it is more suitable for oil spill detection in the downwind scene where the microwave incident direction is similar to the sea surface wind direction and performs well in the scene with incidence angle range from 29.7° to 43.5°

Activation of Triphenylphosphine Oxide Mediated by Trivalent Organouranium Species

Treating a family of uranium benzyl compounds, Tp*₂U­(CH₂Ph) (<b>1-Bn</b>), Tp*₂U­(CH₂-<i>para</i>-^<i>i</i>PrPh) (<b>1-</b>^{<i><b>i</b></i>}<b>Pr</b>), Tp*₂­U­(CH₂-<i>para</i>-^<i>t</i>BuPh) (<b>1-</b>^{<i><b>t</b></i>}<b>Bu</b>), or Tp*₂­U­(CH₂-<i>meta</i>-OMePh) (<b>1-OMe</b>), which are supported by two hydro­tris­(3,5-di­methyl­pyra­zolyl)­borate (Tp*) ligands, with a single equivalent of triphenylphosphine oxide (OPPh₃) causes a unique carbon–carbon coupling to occur. The products of this reaction, Tp*₂U­[OP­(C₆H₅)₂­(C₆H₅­CH₂­C₆H₅)] (<b>2-Ph</b>), Tp*₂U­[OP­(C₆H₅)₂­(C₆H₅­CH₂-<i>p</i>-<i>i</i>Pr­C₆H₄)] (<b>2-</b>^{<i><b>i</b></i>}<b>Pr</b>), Tp*₂U­[OP­(C₆H₅)₂­(C₆H₅­CH₂-<i>p</i>-<i>t</i>Bu­C₆H₄)] (<b>2-</b>^{<i><b>t</b></i>}<b>Bu</b>), and Tp*₂U­[OP­(C₆H₅)₂­(C₆H₅­CH₂-<i>m</i>-OCH_3­C₆H₄)] (<b>2-OMe</b>), are characterized by coupling between the benzyl substituent and the <i>para</i>-carbon of one of the phenyl groups of OPPh₃. To probe the scope of this unusual reactivity, <b>1-Bn</b> was treated with different tris­(aryl)­phos­phine oxides, including tris­(<i>p</i>-tolyl)­phos­phine oxide, which yields Tp*₂U­[OP­(<i>p</i>-tolyl)₂­(C₆H₄­(CH₃)­CH₂­C₆H₅)] (<b>3-tolyl</b>). All compounds were characterized by multinuclear NMR, vibrational, and electronic absorption spectroscopies. When possible, X-ray diffraction was used to confirm molecular structures