Hybrid Materials of the f-Elements Part II

Controlling the Reduction of Chelated Uranyl to Stable Tetravalent Uranium Coordination Complexes in Aqueous Solution

“…This is particularly true for the highly water-soluble uranyl cation, U VI O 2 2+ , which is the predominant form of uranium (U) found in the environment. 6,7 The significant mobility of the uranyl cation introduces risks for radiological contamination, which is a crucial public health issue, as uranium exhibits both chemical and radiological toxicity. 8 Once internalized in the human body, U ions move rapidly throughout the bloodstream and are primarily deposited in the kidney and the skeleton.…”

“…As the use of actinides in both the nuclear power and defense sectors over the past 70 years has resulted in environmental releases of radionuclides generated during associated activities, − the development of aqueous actinide chelation chemistry remains continuously relevant. , Understanding the fundamental bonding interactions of individual actinide cations is critical for ongoing efforts focused on improving actinide decorporation therapies and developing new environmental remediation strategies. This is particularly true for the highly water-soluble uranyl cation, U VI O 2 2+ , which is the predominant form of uranium (U) found in the environment. , The significant mobility of the uranyl cation introduces risks for radiological contamination, which is a crucial public health issue, as uranium exhibits both chemical and radiological toxicity . Once internalized in the human body, U ions move rapidly throughout the bloodstream and are primarily deposited in the kidney and the skeleton. , Clearance following uptake and deposition of U is known to be slow, with decorporation via metal-ion chelation considered the best method for promoting excretion of actinides in vivo .…”

How to Bend the Uranyl Cation via Crystal Engineering

“…that are otherwise inaccessible via traditional coordination chemistry. [1][2][3][4][5][6][7][8][9][10][11][12][13] Within the crystal engineering umbrella is supramolecular assembly, and use of this approach for producing uranyl hybrid materials necessitates a cognizance of the relationship between intra-and intermolecular interactions and resulting global structures. [14][15][16] Judicious selection of uranyl acceptordonor pairings allows for exercising some control over the nature and directionality of non-covalent interactions within uranyl hybrid materials, which is particularly attractive as it allows for tectons and synthons to be selected for, thereby avoiding unpredictable uranyl hydrolysis products.…”

“…As a consequence, we describe the synthesis and characterization of three 'bent' complexes (1-3) featuring 2,4,6-trihalobenzoic acid ligands (where Hal=F, Cl, and Br) and 1,10-phenanthroline (phen), along with nine additional 'non-bent' hybrid materials that either co-formed with the 'bent' complexes (4)(5)(6) or were prepared as part of complementary efforts to understand the mechanism(s) of uranyl bending (7)(8)(9)(10)(11)(12).…”

“…Crystal engineering with the uranyl cation is an area of sustained interest within 5f hybrid materials as it presents a route to access unique structure types and unexpected properties across a range of dimensionalities (i.e., molecular complexes, coordination polymers (CPs), metal–organic frameworks (MOFs), etc.) that are otherwise inaccessible via traditional coordination chemistry. − Within the crystal engineering umbrella is supramolecular assembly, and use of this approach for producing uranyl hybrid materials necessitates a cognizance of the relationship between intra- and intermolecular interactions and resulting global structures. − Judicious selection of uranyl acceptor–donor pairings allows for exercising some control over the nature and directionality of noncovalent interactions within uranyl hybrid materials, which is particularly attractive as it allows for tectons and synthons to be selected for, thereby avoiding unpredictable uranyl hydrolysis products. Our group has recently focused on this problem via the hydrothermal synthesis of discrete, reproducible tectons featuring polypyridyl N-donor capping ligands in the first coordination sphere, which promote a single uranyl species with a specific coordination geometry. − As part of this strategy, N-donor capping ligands are paired with halogen functionalized benzoic acids such that tecton assembly occurs by way of halogen or hydrogen bonding interactions, and moreover, this has proven valuable for systematically engaging the nominally terminal uranyl oxo groups. , …”