Heterobimetallic Uranyl(VI) Alkoxides of Lanthanoids: Formation through simple ligand exchange

Lanthanoid and actinoid silylamides are versatile starting materials. Herein we show how a simple ligand exchange with tert-butanol leads to the formation of the first trimeric heterobimetallic uranyl(VI)-lanthanoid(III) alkoxide complexes....

CARBON NANOPARTICLES BASED ON THERMALLY EXPANDED GRAPHITE: EFFECT OF THE TEG OBTAINING ROUTE ON THE PARTICLES MORPHOLOGY

В работе представлены результаты исследования морфологии углеродных наночастиц, образующихся при жидкофазном расслоении терморасширенного графита в трет-бутаноле. Используемый в работе терморасширенный графит получен путем термического расширения соинтеркалата нитрата графита с уксусной и муравьиной кислотами в режиме термоудара при 500°С и 900 °С. Исходный соинтеркалант по данным рентгенофазового анализа представляет собой смесь соединений II-й и IV-й стадий интеркалирования. Методом просвечивающей электронной микроскопии установлено, что дисперсии углеродных наночастиц, образующиеся при расслоении терморасширенного графита в трет-бутаноле под действием ультразвука, содержат в основном малослойные графены, планарные размеры которых достигают 8 мкм. Обсуждается влияние условий получения терморасширенного графита на морфологию образующихся углеродных наночастиц. Дисперсии на основе терморасширенного графита, полученного при более низкой температуре, помимо малослойных графенов содержат также значительное количество аморфных углеродных частиц с планарными размерами до 100 нм. The paper presents the investigation results of the morphology of carbon nanoparticles formed during liquid-phase exfoliation of thermally expanded graphite in tert-butanol. The thermally expanded graphite used in this work was obtained by thermal expansion of graphite nitrate with acetic and formic acids in the thermal shock mode at 500 °C and 900 °C. Initial cointercalate was shown by powder X-ray diffraction analysis to be the mixture of the II and the IV stage intercalation compounds. It has been established by transmission electron microscopy that dispersions of carbon nanoparticles formed during the exfoliation of thermally expanded graphite in tert-butanol via sonication contain mainly few-layer graphenes, the planar dimensions of which reach 8 pm. The influence of the conditions for thermally expanded graphite obtaining on the morphology of resulting carbon nanoparticles is discussed. Dispersions based on thermally expanded graphite obtained at a lower temperature, in addition to few-layer graphenes, also contain a significant amount of amorphous carbon particles with planar sizes up to 100 nm.

18F-Fluorination Using Tri-Tert-Butanol Ammonium Iodide as Phase-Transfer Catalyst: An Alternative Minimalist Approach

The 18F syntheses of tracers for positron emission tomography (PET) typically require several steps, including extraction of [18F]fluoride from H2[18O]O, elution, and drying, prior to nucleophilic substitution reaction, being a laborious and time-consuming process. The elution of [18F]fluoride is commonly achieved by phase transfer catalysts (PTC) in aqueous solution, which makes azeotropic drying indispensable. The ideal PTC is characterized by a slightly basic nature, its capacity to elute [18F]fluoride with anhydrous solvents, and its efficient complex formation with [18F]fluoride during subsequent labeling. Herein, we developed tri-(tert-butanol)-methylammonium iodide (TBMA-I), a quaternary ammonium salt serving as the PTC for 18F-fluorination reactions. The favorable elution efficiency of [18F]fluoride using TBMA-I was demonstrated with aprotic and protic solvents, maintaining high 18F-recoveries of 96–99%. 18F-labeling reactions using TBMA-I as PTC were studied with aliphatic 1,3-ditosylpropane and aryl pinacol boronate esters as precursors, providing 18F-labeled products in moderate-to-high radiochemical yields. TBMA-I revealed adequate properties for application to 18F-fluorination reactions and could be used for elution of [18F]fluoride with MeOH, omitting an additional base and azeotropic drying prior to 18F-labeling. We speculate that the tert-alcohol functionality of TBMA-I promotes intermolecular hydrogen bonding, which enhances the elution efficiency and stability of [18F]fluoride during nucleophilic 18F-fluorination.