Search Results (7)

Lewis base-free lanthanoid (Ln) and actinoid (An) iodides are difficult to obtain, as standard protocols describe syntheses in solutions of donor solvents which are ultimately hard to remove. We have now established a mechanochemical approach towards the synthesis of Lewis base-free f-block metal iodides with excellent yields. In particular, we describe herein the synthesis of EuI₂ as an example of a divalent lanthanoid iodide, of CeI₃ as an example of a trivalent lanthanoid iodide, and of UI₃ as the most important actinoid iodide. Each can be obtained in high yield with minimal work-up, presenting the most efficient and simple synthetic route to access these materials to date. Full article

α-Aminophosphonates, -phosphinates, and -phosphine oxides are a group of organophosphorus compounds that were investigated as extraction agents for rare earth (RE) metals and actinoids for the first time in the 1960s. However, more systematic investigations of their extraction properties towards REs and actinoids were not started until the 2010s. Indeed, recent studies have shown that these α-amino-functionalized compounds can outperform the commercial organophosphorus extraction agents in RE separations. They have also proven to be very efficient extraction and precipitation agents for recovering Th and U from RE concentrates. These actinoids coexist with REs in some of the commercially important RE-containing minerals. The efficient separation and purification of REs is becoming more and more important every year as these elements have a pivotal role in many existing technologies. If one also considers the facile synthesis of α-amino-functionalized organophosphorus extractants and precipitation agents, it is expected that they will be increasingly utilized in the extraction chemistry of REs and actinoids in the future. This review collates α-aminophosphonates, -phosphinates, and -phosphine oxides that have been utilized in the separation chemistry of REs and actinoids, including their most relevant synthetic routes and molecular properties. Their extraction and precipitation properties towards REs and actinoids are also discussed. Full article

Deferoxamine B is an outstanding molecule which has been widely studied in the past decade for its ability to bind iron and many other metal ions. The versatility of this metal chelator makes it suitable for a number of medicinal and analytical applications, from the well-known iron chelation therapy to the most recent use in sensor devices. The three bidentate hydroxamic functional groups of deferoxamine B are the centerpiece of its metal binding ability, which allows the formation of stable complexes with many transition, lanthanoid and actinoid metal ions. In addition to the ferric ion, in fact, more than 20 different metal complexes of deferoxamine b have been characterized in terms of their chemical speciation in solution. In addition, the availability of a terminal amino group, most often not involved in complexation, opens the way to deferoxamine B modification and functionalization. This review aims to collect and summarize the available data concerning the complex-formation equilibria in solutions of deferoxamine B with different metal ions. A general overview of the progress of its applications over the past decade is also discussed, including the treatment of iron overload-associated diseases, its clinical use against cancer and neurodegenerative disorders and its role as a diagnostic tool. Full article

EXAFS spectroscopy is one of the most used techniques to solve the structure of actinoid solutions. In this work a systematic analysis of the EXAFS spectra of four actinyl cations, [UO₂]²⁺, [NpO₂]²⁺, [NpO₂]⁺ and [PuO₂]²⁺ has been carried out by comparing experimental results with theoretical spectra. These were obtained by averaging individual contributions from snapshots taken from classical Molecular Dynamics simulations which employed a recently developed [AnO₂]^2+/+ –H₂O force field based on the hydrated ion model using a quantum-mechanical (B3LYP) potential energy surface. Analysis of the complex EXAFS signal shows that both An-O${}_{\mathrm{yl}}$ and An-O${}_{\mathrm{W}}$ single scattering paths as well as multiple scattering ones involving [AnO₂]^+/2+ molecular cation and first-shell water molecules are mixed up all together to produce a very complex signal. Simulated EXAFS from the B3LYP force field are in reasonable agreement for some of the cases studied, although the k= 6–8 Å${}^{-1}$ region is hard to be reproduced theoretically. Except uranyl, all studied actinyls are open-shell electron configurations, therefore it has been investigated how simulated EXAFS spectra are affected by minute changes of An-O bond distances produced by the inclusion of static and dynamic electron correlation in the quantum mechanical calculations. A [NpO₂]⁺−H₂O force field based on a NEVPT2 potential energy surface has been developed. The small structural changes incorporated by the electron correlation on the actinyl aqua ion geometry, typically smaller than 0.07 Å, leads to improve the simulated spectrum with respect to that obtained from the B3LYP force field. For the other open-shell actinyls, [NpO₂]²⁺ and [PuO₂]²⁺, a simplified strategy has been adopted to improve the simulated EXAFS spectrum. It is computed taking as reference structure the NEVPT2 optimized geometry and including the DW factors of their corresponding MD simulations employing the B3LYP force field. A better agreement between the experimental and the simulated EXAFS spectra is found, confirming the a priori guess that the inclusion of dynamic and static correlation refine the structural description of the open-shell actinyl aqua ions. Full article

Even 155 years after their first synthesis, Schiff bases continue to surprise inorganic chemists. Schiff-base ligands have played a major role in the development of modern coordination chemistry because of their relevance to a number of interdisciplinary research fields. The chemistry, properties and applications of transition metal and lanthanoid complexes with Schiff-base ligands are now quite mature. On the contrary, the coordination chemistry of Schiff bases with actinoid (5f-metal) ions is an emerging area, and impressive research discoveries have appeared in the last 10 years or so. The chemistry of actinoid ions continues to attract the intense interest of many inorganic groups around the world. Important scientific challenges are the understanding the basic chemistry associated with handling and recycling of nuclear materials; investigating the redox properties of these elements and the formation of complexes with unusual metal oxidation states; discovering materials for the recovery of trans-{U^VIO₂}²⁺ from the oceans; elucidating and manipulating actinoid-element multiple bonds; discovering methods to carry out multi-electron reactions; and improving the 5f-metal ions’ potential for activation of small molecules. The study of 5f-metal complexes with Schiff-base ligands is a currently “hot” topic for a variety of reasons, including issues of synthetic inorganic chemistry, metalosupramolecular chemistry, homogeneous catalysis, separation strategies for nuclear fuel processing and nuclear waste management, bioinorganic and environmental chemistry, materials chemistry and theoretical chemistry. This almost-comprehensive review, covers aspects of synthetic chemistry, reactivity and the properties of dinuclear and oligonuclear actinoid complexes based on Schiff-base ligands. Our work focuses on the significant advances that have occurred since 2000, with special attention on recent developments. The review is divided into eight sections (chapters). After an introductory section describing the organization of the scientific information, Sections 2 and 3 deal with general information about Schiff bases and their coordination chemistry, and the chemistry of actinoids, respectively. Section 4 highlights the relevance of Schiff bases to actinoid chemistry. Sections 5–7 are the “main menu” of the scientific meal of this review. The discussion is arranged according the actinoid (only for Np, Th and U are Schiff-base complexes known). Sections 5 and 7 are further arranged into parts according to the oxidation states of Np and U, respectively, because the coordination chemistry of these metals is very much dependent on their oxidation state. In Section 8, some concluding comments are presented and a brief prognosis for the future is attempted. Full article