A Thorium Metal-Organic Framework with Outstanding Thermal and Chemical Stability.

A new thorium metal-organic framework (MOF), Th(OBA)2 , where OBA is 4,4'-oxybis(benzoic) acid, has been synthesized hydrothermally in the presence of a range of nitrogen-donor coordination modulators. This Th-MOF, described herein as GWMOF-13, has been characterized by single-crystal and powder X-ray diffraction, as well as through a range of techniques including gas sorption, thermogravimetric analysis (TGA), solid-state UV/Vis and luminescence spectroscopy. Single-crystal X-ray diffraction analysis of GWMOF-13 reveals an interesting, high symmetry (cubic Ia 3 ‾ d) structure, which yields a novel srs-a topology. Most notably, TGA analysis of GWMOF-13 reveals framework stability to 525 °C, matching the thermal stability benchmarks of the UiO-66 series MOFs and zeolitic imidazolate frameworks (ZIFs), and setting a new standard for thermal stability in f-block based MOFs

Selective Lanthanide Sensing with Gold Nanoparticles and Hydroxypyridinone Chelators.

The octadentate hydroxypyridinone chelator 3,4,3-LI(1,2-HOPO) is a promising therapeutic agent because of its high affinity for f-block elements and noncytotoxicity at medical dosages. The interaction between 3,4,3-LI(1,2-HOPO) and other biomedically relevant metals such as gold, however, has not been explored. Gold nanoparticles functionalized with chelators have demonstrated great potential in theranostics, yet thus far, no protocol that combines 3,4,3-LI(1,2-HOPO) and colloidal gold has been developed. Here, we characterize the solution thermodynamic properties of the complexes formed between 3,4,3-LI(1,2-HOPO) and Au3+ ions and demonstrate how under specific pH conditions the chelator promotes the growth of gold nanoparticles, acting as both reducing and stabilizing agent. 3,4,3-LI(1,2-HOPO) ligands on the nanoparticle surface remain active and selective toward f-block elements, as evidenced by gold nanoparticle selective aggregation. Finally, a new colorimetric assay capable of reaching the detection levels necessary for the quantification of lanthanides in waste from industrial processes is developed based on the inhibition of particle growth by lanthanides

Spontaneous Chelation-Driven Reduction of the Neptunyl Cation in Aqueous Solution.

Octadentate hydroxypyridinone (HOPO) and catecholamide (CAM) siderophore analogues are known to be efficacious chelators of the actinide cations, and these ligands are also capable of facilitating both activation and reduction of actinyl species. Utilizing X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies, as well as cyclic voltammetry measurements, herein, we elucidate chelation-based mechanisms for driving reactivity and initiating redox processes in a family of neptunyl-HOPO and CAM complexes. Based on the selected chelator, the ability to control the oxidation state of neptunium and the speed of reduction and concurrent oxo group activation was demonstrated. Most notably, reduction kinetics for the NpV O2 +/ /NpIV redox couple upon chelation by the ligands 3,4,3-LI(1,2-HOPO) and 3,4,3-LI(CAM)2 (1,2-HOPO)2 was observed to be faster than ever reported, and in fact quicker than we could measure using either X-ray absorption spectroscopy or electrochemical techniques

Controlling Dimensionality Via A Dual Ligand Strategy In Ln-thiophene-2,5-dicarboxylic Acid-terpyridine Coordination Polymers

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Eleven new lanthanide (Ln = Nd-Lu)-thiophene-2,5-dicarboxylic acid (25-TDC)-2,2':6',2 ''-terpyridine (terpy) coordination polymers (1-11) which employ a dual ligand strategy have been synthesized hydrothermally and structurally characterized by single crystal and powder X-ray diffraction. Two additional members of the series (12 and 13) were made with Ce3+ and Pr3+ and characterized via powder X-ray diffraction only. The series is comprised of three similar structures wherein differences due to the lanthanide contraction manifest in Ln(3+) coordination number as well as the number of bound and solvent water molecules within the crystal lattice. Structure type I (Ce3+-Sm3+) contains two nine-coordinate Ln(3+) metal centers each with a bound water molecule. Structure type II (Eu3+-Ho3+) features a nine and an eight coordinate Ln(3+) metal along with one bound and one solvent water molecule. Structure type III (Er3+-Lu3+) includes two eight-coordinate Ln(3+) metal centers with both water molecules residing in the lattice. Assembly into supramolecular 3D networks via p-p interactions is observed for all three structure types, whereas structure types II and III also feature hydrogen-bonding interactions via the well-known C-H center dot center dot center dot O and O-H center dot center dot center dot O synthons. Visible and near-IR luminescence studies were performed on compounds 1, 2, 10, and 13 at room temperature. As a result characteristic near-IR luminescent bands of Pr3+, Nd3+, Sm3+, and Yb3+ as well as visible bands of Sm3+ were observed.44361584315854Material Science of Actinides, an Energy Frontier Research Center - U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-SC0001089]George Washington UniversityCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CAPES [4671120]FAPESP [2009/54066-7

Exploring the promotion of synthons of choice: halogen bonding in molecular lanthanide complexes characterized via X-ray diffraction, luminescence spectroscopy, and magnetic measurements

Promotion of a synthon of choice for the non-covalent assembly of lanthanide tectons represents both a noteworthy challenge and opportunity within LnIII hybrid materials. We have developed a system, wherein some control can be exercised over supramolecular assembly and, as part of continued efforts to improve this process we have generated a family of ten new lanthanide (Ln = Sm3+ – Lu3+) 2,4,6-trichlorobenzoic acid-1,10-phenanthroline molecular complexes. Delineation of criteria for promoting assembly via halogen based interactions was introduced previously and is refined herein based on the characterization of complexes 1–10 via single-crystal X-ray diffraction. Direct comparison of means of supramolecular assembly for 1–10 with isostructural Ln-p-chlorobenzoic acid-1,10-phenanthroline analogues verifies that increasing the number of halogen atoms at the periphery of a tecton is one route that increases the frequency of halogen bonding interactions. Additionally, solid-state visible and near-IR photoluminescence and luminescent lifetime data were collected for complexes 1 (Sm3+), 2 (Eu3+), 4 (Tb3+), 5 (Dy3+), 6 (Ho3+), 7 (Er3+), and 9 (Yb3+) and characteristic emission was observed for all complexes except 6. Further, direct current magnetic susceptibility measurements were carried out for complexes 5 (Dy3+) and 7 (Er3+), and two slow magnetic relaxation processes were characterized using alternating current magnetic susceptibility measurements for 5