Daniel Meyer

Metallorganische Chemie des Technetiums: VIII. Technetium(I)-carbonyl-Komplexe mit Polypyrazol-1-yl-borato-Liganden im Vergleich mit seinen Mn- und Re-Homologen

Abstract The compounds HB(C3H3N2)3Tc(CO)3 and HB(3,5-Me2C3HN2)3Tc(CO)3 have been synthesized for the first time, and their molecular and crystal structure as well as the structures of the known analogous compounds of manganese and rhenium determined by single-crystal X-ray diffraction. The IR-, 1H-NMR-, 13C-NMR-, UV- and EI-MS-spectroscopic data are discussed in correlation to the electric dipole moment and the charge distribution within the molecule.

Non‐aqueous Synthesis of Isotropic and Anisotropic Actinide Oxide Nanocrystals

The huge interest of the scientific community in the controlled synthesis, structural characterization and assembly into 2and 3-dimensional architectures of nano-objects as well as investigations of their corresponding chemical and physical properties cannot be denied anymore. Within the past two decades, it has been shown that size reduction means more than simply making things smaller. Indeed, size decreasing (as well as shape controlling) is a powerful way to tune materials properties (magnetic, electronic, optical, catalytic, etc.). Whereas nanoscience is a very active field when one considers stable elements, it is still in its infancy when dealing with radioactive actinides. Actinide compounds are important in the nuclear industry and actinide-based nano-objects could be used as new building blocks for the preparation of innovative nuclear fuels or as model systems to study the migration of radionuclides in the environment (e.g., in nuclear waste disposal). The actinide series is also characterized by the emergence of 5f electrons in the valence shell. The behaviour of the 5f electrons determines the solid-sate properties of the actinides and their compounds. Compared to the stable elements, questions related to size and shape effects on the physical and chemical properties of actinide compounds are still open and should find their way into the nanoscience. Accordingly, our main goal is dedicated to the controlled synthesis, the structural characterization and the investigation of the properties of actinide-based nano-objects. Here, we report on the controlled synthesis of uranium oxide and thorium oxide nanocrystals (NCs) by a non-aqueous approach. The obtained NCs have been characterized by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The results of this study therefore present an important step for moving to the preparation of transuranium oxide NCs (e.g., NpO2, PuO2). Uranium and thorium oxide NCs were synthesized by the so-called “heating-up” method by using standard air-free techniques. Uranyl acetylacetonate (UO2ACHTUNGTRENNUNG(acac)2) or thorium acetylacetonate (ThACHTUNGTRENNUNG(acac)4) are introduced in a degassed mixture of dibenzyl ether (BnOBn) with different concentrations of stabilizing agents, like oleic acid (OA), oleylACHTUNGTRENNUNGamine (OAm), trioctylamine (N ACHTUNGTRENNUNG(Oct)3) and trioctylphosphine oxide (OP ACHTUNGTRENNUNG(Oct)3). The resulting mixtures are then heated up to 280 8C. After being cooled to room temperature, the NCs are precipitated with ethanol followed by centrifugation and re-dispersion in toluene. Surprisingly, the experimental conditions well-suited for the formation of uranium oxide NCs cannot be applied when considering the formation of thorium oxide NCs. The modification of the reactivity (for a given organic system) as a function of the nature of the actinide precursor and/or the actinide centre seems to be essential when taking into account the synthesis of actinide oxide NCs. Because of these differences in the reactivity of uranium and thorium precursors, different solvent compositions were tested in order to find the best reaction conditions to obtain well defined NCs. A black precipitate can be isolated from the reaction of UO2ACHTUNGTRENNUNG(acac)2 in a mixture of BnOBn/OA/OAm. The PXRD data of the as-prepared compound along with the corresponding Rietveld refinement are presented in Figure 1 a. The PXRD pattern exhibits Bragg reflections characteristic of the fluorite structure (space group Fm-3m). The experimental PXRD pattern was calculated by using the bulk structure of uranium dioxide (UO2). The detailed results of the Rietveld refinement are given in the Supporting Information. The peak broadening is the result of the small size of the coherent domains (the crystallites), which has been estimated with the fundamental approach to be 4.5 nm. Under the same experimental conditions (i.e., BnOBn/ OA/OAm), the reaction of ThACHTUNGTRENNUNG(acac)4 did not give rise to the formation of thorium-based NCs. Indeed, in the presence of [a] Dr. D. Hudry, Dr. C. Apostolidis, Dr. O. Walter, Dr. T. Gouder European Commission: Joint Research Center Institute for Transuranium Elements, P. O. Box 2340 76125 Karlsruhe (Germany) Fax: (+49) 7247-951-599 E-mail : damien.hudry@ec.europa.eu damien.hudry@gmail.com [b] Dr. E. Courtois, Dr. C. K bel Karlsruhe Institute of Technology, Institute of Nanotechnology Hermann-von-Helmholtz-Platz 1 76344 Eggenstein–Leopoldshafen (Germany) [c] Dr. C. K bel Karlsruhe Nano Micro Facility, Hermann-von-Helmholtz-Platz 1 76344 Eggenstein–Leopoldshafen (Germany) [d] Dr. D. Meyer Institut de Chimie S parative de Marcoule, UMR 5257 BP 17171, 30207 Bagnols sur C ze Cedex (France) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201200513.

Controlled Synthesis of Thorium and Uranium Oxide Nanocrystals

Very little is known about the size and shape effects on the properties of actinide compounds. As a consequence, the controlled synthesis of well-defined actinide-based nanocrystals constitutes a fundamental step before studying their corresponding properties. In this paper, we report on the non-aqueous surfactant-assisted synthesis of thorium and uranium oxide nanocrystals. The final characteristics of thorium and uranium oxide nanocrystals can be easily tuned by controlling a few experimental parameters such as the nature of the actinide precursor and the composition of the organic system (e.g., the chemical nature of the surfactants and their relative concentrations). Additionally, the influence of these parameters on the outcome of the synthesis is highly dependent on the nature of the actinide element (thorium versus uranium). By using optimised experimental conditions, monodisperse isotropic uranium oxide nanocrystals with different sizes (4.5 and 10.7u2005nm) as well as branched nanocrystals (overall size ca. 5u2005nm), nanodots (ca. 4u2005nm) and nanorods (with ultra-small diameters of 1u2005nm) of thorium oxide were synthesised.

Thorium/uranium mixed oxide nanocrystals: Synthesis, structural characterization and magnetic properties

One of the primary aims of the actinide community within nanoscience is to develop a good understanding similar to what is currently the case for stable elements. As a consequence, efficient, reliable and versatile synthesis techniques dedicated to the formation of new actinide-based nano-objects (e.g. nanocrystals) are necessary. Hence, a “library” dedicated to the preparation of various actinidebased nanoscale building blocks is currently being developed. Nanoscale building blocks with tunable sizes, shapes and compositions are of prime importance. So far, the non-aqueous synthesis method in highly coordinating organic media is the only approach which has demonstrated the capability to provide size and shape control of actinide-based nanocrystals (both for thorium and uranium, and recently extended to neptunium and plutonium). In this paper, we demonstrate that the non-aqueous approach is also well adapted to control the chemical composition of the nanocrystals obtained when mixing two different actinides. Indeed, the controlled hot co-injection of thorium acetylacetonate and uranyl acetate (together with additional capping agents) into benzyl ether can be used to synthesize thorium/uranium mixed oxide nanocrystals covering the full compositional spectrum. Additionally, we found that both size and shape are modified as a function of the thorium:uranium ratio. Finally, the magnetic properties of the different thorium/uranium mixed oxide nanocrystals were investigated. Contrary to several reports, we did not observe any ferromagnetic behavior. As a consequence, ferromagnetism cannot be described as a universal feature of nanocrystals of non-magnetic oxides as recently claimed in the literature.

Ultra-Small Plutonium Oxide Nanocrystals: An Innovative Material in Plutonium Science

Apart from its technological importance, plutonium (Pu) is also one of the most intriguing elements because of its non-conventional physical properties and fascinating chemistry. Those fundamental aspects are particularly interesting when dealing with the challenging study of plutonium-based nanomaterials. Here we show that ultra-small (3.2±0.9u2005nm) and highly crystalline plutonium oxide (PuO2 ) nanocrystals (NCs) can be synthesized by the thermal decomposition of plutonyl nitrate ([PuO2 (NO3 )2 ]⋅3u2009H2 O) in a highly coordinating organic medium. This is the first example reporting on the preparation of significant quantities (several tens of milligrams) of PuO2 NCs, in a controllable and reproducible manner. The structure and magnetic properties of PuO2 NCs have been characterized by a wide variety of techniques (powder X-ray diffraction (PXRD), X-ray absorption fine structure (XAFS), X-ray absorption near edge structure (XANES), TEM, IR, Raman, UV/Vis spectroscopies, and superconducting quantum interference device (SQUID) magnetometry). The current PuO2 NCs constitute an innovative material for the study of challenging problems as diverse as the transport behavior of plutonium in the environment or size and shape effects on the physics of transuranium elements.

Metallorganische chemie des technetiums XII. Photolytische CO-substitutionsreaktionen von technetiumtricarbonylverbindungen. Synthesen und Röntgenstrukturanalysen von (C5H5)Tc(CO)3(PPh3), (C5Me5)Tc(CO)2(PPh3) und [HB(3,5-Me2 Pz)3Tc(CO) 2[P(OMe)3] im Vergleich mit seinen Homologen

Abstract Photochemical reactions of technetiumtricarbonyl compounds with neutral phosphorous donor ligands are reported. (C 5 Me 5 )Tc(CO) 3 and (C 5 H 5 )Tc(CO) 3 react with triphenylphosphane to yield (C 5 Me 5 )Tc(CO) 2 (PPh 3 ) ( 3 ) and (C 5 H 5 )Tc(CO) 2 (PPh 3 ) ( 4 ) respectively. 3 and 4 have been isolated and their molecular and crystal structures were determined by single-crystal X-ray diffraction. The crystal structures of the yellow compounds 3 (monoclinic) and 4 (triclinic) are discussed together with their spectroscopic data and are compared with the also determined structure of the homologous rhenium compound (C 5 Me 5 )Re(CO) 2 (PPh 3 ) ( 3a ). Thermal in-situ reaction of irradiated HB(3,5-Me 2 C 3 HN 2 )Tc(CO) 3 with trimethylphosphite (TMP) yields HB(3,5-Me 2 C 3 HN 2 )Tc(CO) 2 (TMP) ( 7 ). The crystal and molecular structure of 7 was determined and and is discussed in comparison with the determined structures of the homologous compounds HB(3,5-Me 2 C 3 HN 2 )Re(CO) 2 (TMP) ( 7a ), and HB(3,5-Me 2 C 3 HN 2 )Mn(CO) 2 (TMP) ( 7b ). The intermediate Re-compound HB(3,5-Me 2 C 3 HN 2 )Re(CO) 2 (THF) ( 8a ) has been also isolated and characterized.

Synthesis of transuranium-based nanocrystals via the thermal decomposition of actinyl nitrates

In this communication, we report on the use of easily accessible actinide precursors to synthesize actinide oxide nanocrystals. Uranyl and neptunyl nitrates have been successfully used as starting materials in the non-aqueous synthesis of AnO2 (An = U, Np) nanocrystals. This communication reports for the first time on the formation of transuranium-based nanocrystals.

Metallorganische Chemie des Technetiums: X. Synthese, Charakterisierung und Röntgenstrukturanalyse von μ-Distickstoff-bis[hydrotris(3,5-dimethylpyrazolyl)-borato-technetium-dicarbonyl], [L★Tc(CO)2]2(μ-N2)☆

Abstract The compound [HB(3,5-Me2C3N2)3]Tc(CO)3 reacts after UV irradiation in THF with elementary nitrogen to give the air-stable N2-bridged binuclear complex {[HB(3,5-Me2C3N2)3]Tc(CO)2}2(μ-N2). The crystal and molecular structure of this first N2-bridged organometallic technetium complex has been determined by a single-crystal X-ray diffraction study. The compound crystallizes monoclinic (space group C2/c) with cell parameters a 2032.2(6), b 1454.7(4) and c 1427.0(5) pm and Z = 4. The Nue5f8N distance is 116.0 pm and the Tcue5f8Nue5f8N angle is 174.0°. The IR, 1H NMR, UV and EI-MS spectroscopic data are discussed.

Tuning Selectivity of Fluorescent Carbon Nanotube-Based Neurotransmitter Sensors

Detection of neurotransmitters is an analytical challenge and essential to understand neuronal networks in the brain and associated diseases. However, most methods do not provide sufficient spatial, temporal, or chemical resolution. Near-infrared (NIR) fluorescent single-walled carbon nanotubes (SWCNTs) have been used as building blocks for sensors/probes that detect catecholamine neurotransmitters, including dopamine. This approach provides a high spatial and temporal resolution, but it is not understood if these sensors are able to distinguish dopamine from similar catecholamine neurotransmitters, such as epinephrine or norepinephrine. In this work, the organic phase (DNA sequence) around SWCNTs was varied to create sensors with different selectivity and sensitivity for catecholamine neurotransmitters. Most DNA-functionalized SWCNTs responded to catecholamine neurotransmitters, but both dissociation constants (Kd) and limits of detection were highly dependent on functionalization (sequence). Kd values span a range of 2.3 nM (SWCNT-(GC)15 + norepinephrine) to 9.4 μM (SWCNT-(AT)15 + dopamine) and limits of detection are mostly in the single-digit nM regime. Additionally, sensors of different SWCNT chirality show different fluorescence increases. Moreover, certain sensors (e.g., SWCNT-(GT)10) distinguish between different catecholamines, such as dopamine and norepinephrine at low concentrations (50 nM). These results show that SWCNTs functionalized with certain DNA sequences are able to discriminate between catecholamine neurotransmitters or to detect them in the presence of interfering substances of similar structure. Such sensors will be useful to measure and study neurotransmitter signaling in complex biological settings.

Metallorganische chemie des technetiums: XI. Synthese, charakterisierung und röntgenstrukturanalyse von η5-tetramethylazacyclopentadienyltechnetiumtricarbonyl (Me4C4N)Tc(CO)3·HNC4Me4 und seinen Mn- und Re-homologen

Abstract The heterocyclic “half-sandwich”-compounds η5-(Me4C4N)M(CO)3·HNC4Me4 of manganese, technetium and rhenium have been synthesized by reaction of tetramethylpyrrolyl potassium, (Me4C4N)K, with BrM(CO)5(M = Mn, Tc, Re) in THF. The products were isolated and characterized by IR, UV/VIS, EI-MS and 1H-NMR spectroscopy. The crystal and molecular structure of the three compounds were determined by single-crystal X-ray diffraction. The technetium and rhenium compounds crystallize orthorhombic with four molecules per elementary cell. The manganese compound crystallizes monoclinic with eight molecules per elementary cell, which belong to two discrete types of molecules. A tetramethylpyrrolylring is η5-coordinated to the M(CO)3-fragment, and a free tetramethylpyrrole is bonded to the nitrogen atom of the η5-bonded pyrrolylring by a hydrogen-bridged bond.