Slow Magnetic Relaxation in a Californium Complex.

We report the synthesis and characterization of the macrocyclic californium derivative Na[Cf(HO)(DOTA)] (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate), , which was studied in comparison to its dysprosium counterpart, Na[Dy(HO)(DOTA)], . Divergent spectroscopic and magnetic behaviors were observed between and . Based upon spectroscopic measurements, we propose that accessible 5f → 6d transitions (potentially operating in tandem with charge-transfer transitions) are the major contributors to the observed broadband photoluminescence in .

Improved Energy Transfer in the Sensitization of Americium Enables Observation of Circularly Polarized Luminescence.

The first example of circularly polarized luminescence (CPL) from a molecular americium (Am) complex is reported. Coordination of Am(III) by a combination of thenoyltrifluoroacetonate and a chiral diphosphine oxide ligand yielded a complex with strong sensitized metal-centered luminescence. The energy transfer process for sensitization appears to occur via a unique resonant pathway, which results in the removal of the overlap between ligand phosphorescence and sensitized Am luminescence that has often been observed.

Isolation of a chloride-capped cerium polyoxo nanocluster built from 52 metal ions.

Four cerium compounds - (HPy)[CeCl]·2(HPyCl) (Ce1-1), (HPy)[CeCl] (Ce1-2), (HPy)[CeO(OH)Cl(HO)]·HO (Ce38), and (HPy)[CeO(OH)Cl(HO)]·HO (Ce52) - were crystallized from acidic aqueous solutions using pyridinium (HPy) counterions. The latter consists of two unique cerium oxide nanoclusters that are built from 52 metal ions and represents the largest chloride capped {CeO} and/or {MO} (M = Ce, Th, U, Np, Pu) nanocluster that adopts the fluorite-type structure of MO that has been reported.

PuCl{CoCp[OP(OEt)]}: transuranic elements entering the field of heterometallic molecular chemistry.

Recent advances enabled the discovery of heterometallic molecules for many metals: main group, d-block, lanthanides, and some actinides (U, Th). These complexes have at least two different metals joined by bridging ligands or by direct metal-metal bonding interactions. They are attractive because they can enable chemical cooperativity between metals from different parts of the periodic table.

Actinium chelation and crystallization in a macromolecular scaffold.

Targeted alpha therapy (TAT) pairs the specificity of antigen targeting with the lethality of alpha particles to eradicate cancerous cells. Actinium-225 [Ac; t = 9.920(3) days] is an alpha-emitting radioisotope driving the next generation of TAT radiopharmaceuticals.

Macrocyclic 1,2-Hydroxypyridinone-Based Chelators as Potential Ligands for Thorium-227 and Zirconium-89 Radiopharmaceuticals.

Thorium-227 (Th) is an α-emitting radionuclide that has shown preclinical and clinical promise for use in targeted α-therapy (TAT), a type of molecular radiopharmaceutical treatment that harnesses high energy α particles to eradicate cancerous lesions. Despite these initial successes, there still exists a need for bifunctional chelators that can stably bind thorium in vivo. Toward this goal, we have prepared two macrocyclic chelators bearing 1,2-hydroxypyridinone groups.

Siderocalin fusion proteins enable a new Y/Y theranostic approach.

The mammalian protein siderocalin binds bacterial siderophores and their iron complexes through cation-π and electrostatic interactions, but also displays high affinity for hydroxypyridinone complexes of trivalent lanthanides and actinides. In order to circumvent synthetic challenges, the use of siderocalin-antibody fusion proteins is explored herein as an alternative targeting approach for precision delivery of trivalent radiometals. We demonstrate the viability of this approach , using the theranostic pair Y (β, = 64 h)/Y (β, = 14.

Structure and Dynamics of NaCl/KCl/CaCl-EuCl ( = 2, 3) Molten Salts.

Modern molten salt reactor design and the techniques of electrorefining spent nuclear fuels require a better understanding of the chemical and physical behavior of lanthanide/actinide ions with different oxidation states dissolved in various solvent salts. The molecular structures and dynamics that are driven by the short-range interactions between solute cations and anions and long-range solute and solvent cations are still unclear. In order to study the structural change of solute cations caused by different solvent salts, we performed first-principles molecular dynamics simulations in molten salts and extended X-ray absorption fine structure (EXAFS) measurements for the cooled molten salt samples to identify the local coordination environment of Eu and Eu ions in CaCl, NaCl, and KCl.

Evaluation of Ce as a PET imaging surrogate for antibody drug conjugates incorporating Ac.

Introduction: The in vivo generator Ce/La has the potential to serve as a PET imaging surrogate for both alpha-emitting Ac and Th radionuclides due to the unique Ce/Ce redox couple and the relatively long half-life of Ce. The purpose of this study was to demonstrate the compatibility of Ce with DOTA-based antibody drug conjugates, which would act as therapeutic agents when incorporating Ac.

Methods: The in vivo biodistributions of [Ce]Ce-DOTA and [Ce]Ce-citrate were assayed by microPET imaging over 25 h in Swiss Webster mice to determine the in vivo stability of the [Ce]Ce-DOTA complex.

In situ beam reduction of Pu(IV) and Bk(IV) as a route to trivalent transuranic coordination complexes with hydroxypyridinone chelators.

The solution-state interactions of plutonium and berkelium with the octadentate chelator 3,4,3-LI(1,2-HOPO) (343-HOPO) were investigated and characterized by X-ray absorption spectroscopy, which revealed in situ reductive decomposition of the tetravalent species of both actinide metals to yield Pu(III) and Bk(III) coordination complexes. X-ray absorption near-edge structure (XANES) measurements were the first indication of in situ synchrotron redox chemistry as the Pu threshold and white-line position energies for Pu-343-HOPO were in good agreement with known diagnostic Pu(III) species, whereas Bk-343-HOPO results were found to mirror the XANES behavior of Bk(III)-DTPA. Extended X-ray absorption fine structure results revealed An-O bond distances of 2.

Reactivity of a Chloride Decorated, Mixed Valent Ce-Oxo Cluster.

A cerium-oxo nanocluster capped by chloride ligands, [CeCeO(OH)Cl(HO)] ( = 1-24), has been isolated from acidic chloride solutions by using potassium counterions. The crystal structure was elucidated using single crystal X-ray diffraction. At the center of the cluster is a {Ce} core that exhibits the same fluorite-type structure as bulk CeO, with eight-coordinate Ce sites bridged by tetrahedral oxo anions.

Using molten salts to probe outer-coordination sphere effects on lanthanide(III)/(II) electron-transfer reactions.

Controlling structure and reactivity by manipulating the outer-coordination sphere around a given reagent represents a longstanding challenge in chemistry. Despite advances toward solving this problem, it remains difficult to experimentally interrogate and characterize outer-coordination sphere impact. This work describes an alternative approach that quantifies outer-coordination sphere effects.

Advancing understanding of actinide(iii) (Ac, Am, Cm) aqueous complexation chemistry.

The positive impact of having access to well-defined starting materials for applied actinide technologies - and for technologies based on other elements - cannot be overstated. Of numerous relevant 5f-element starting materials, those in complexing aqueous media find widespread use. Consider acetic acid/acetate buffered solutions as an example.

Impact of Noncovalent Interactions on the Structural Chemistry of Thorium(IV)-Aquo-Chloro Complexes.

Five novel tetravalent thorium (Th) compounds that consist of Th(HO)Cl structural units were isolated from acidic aqueous solutions using a series of nitrogen-containing heterocyclic hydrogen (H) bond donors. Taken together with three previously reported phases, the compounds provide a series of monomeric Th complexes wherein the effects of noncovalent interactions (and H-bond donor identity) on Th structural chemistry can be examined. Seven distinct structural units of the general formulas [Th(HO)Cl] ( = 2, 4) and [Th(HO)Cl] ( = 5-7) are described.

Structural and spectroscopic characterization of an einsteinium complex.

The transplutonium elements (atomic numbers 95-103) are a group of metals that lie at the edge of the periodic table. As a result, the patterns and trends used to predict and control the physics and chemistry for transition metals, main-group elements and lanthanides are less applicable to transplutonium elements. Furthermore, understanding the properties of these heavy elements has been restricted by their scarcity and radioactivity.

Mononuclear to Polynuclear U Structural Units: Effects of Reaction Conditions on U-Furoate Phase Formation.

Uranium(IV) complexation by 2-furoic acid (2-FA) was examined to better understand the effects of ligand identity and reaction conditions on species formation and stability. Five compounds were isolated: [UCl (2-FA) (H O) ] (1), [U Cl O (THF) (2-FA) ]⋅2 THF (2), [U O (OH) (H O) (2-FA) ]⋅7 THF⋅H O (3), [U O (OH) (H O) (2-FA) ]⋅8.76 H O (4), and [U Cl O (OH) (H O) ]⋅m H O⋅n THF (5).

Monomeric and Trimeric Thorium Chlorides Isolated from Acidic Aqueous Solution.

Two thorium(IV) compounds, [Th(HO)Cl]·2(HPy·Cl) () and (HPy)[Th(HO)Cl(OH)]·4(HPy·Cl) () (HPy = pyridinium), were isolated from acidic aqueous solution. The compounds were synthesized at room temperature and subsequently characterized using single crystal X-ray diffraction along with Raman and IR spectroscopies. Whereas compound is built from discrete mononuclear Th(HO)Cl units, compound consists of a novel hydroxo-bridged trimeric [Th(OH)] core.

From Thorium to Plutonium: Trends in Actinide(IV) Chloride Structural Chemistry.

A series of eighteen tetravalent actinide (An = Th, U, Pu) compounds were synthesized from acidic aqueous solutions containing thorium, uranium, or plutonium and a series of protonated nitrogen heterocycles. The compounds were characterized using Raman, IR, and optical absorption spectroscopies. The structures were determined using single-crystal X-ray diffraction and found to consist of [An(HO)Cl] ( = 4-7 and = 2-4) or AnCl molecular units.

Solution and Solid State Structural Chemistry of Th(IV) and U(IV) 4-Hydroxybenzoates.

Organic ligands with carboxylate functionalities have been shown to affect the solubility, speciation, and overall chemical behavior of tetravalent metal ions. While many reports have focused on actinide complexation by relatively simple monocarboxylates such as amino acids, in this work we examined Th(IV) and U(IV) complexation by 4-hydroxybenzoic acid in water with the aim of understanding the impact that the organic backbone has on the solution and solid state structural chemistry of thorium(IV) and uranium(IV) complexes. Two compounds of the general formula [AnO(OH)(HO)(4-HB)]· nHO [An = Th (Th-1) and U (U-1); 4-HB = 4-hydroxybenzoate] were synthesized via room-temperature reactions of AnCl and 4-hydroxybenzoic acid in water.

Uranium(IV) Chloride Complexes: UCl and an Unprecedented U(HO)Cl Structural Unit.

The room temperature synthesis and structural characterization of two U(IV) compounds isolated from acidic aqueous solution is reported. Evaporation of a U(IV)/HCl solution containing pyridinium (HPy) yielded (HPy)UCl (1), yet in the presence of an organic carboxylate U(HO)Cl·(HPy·Cl) (2) is obtained. The structures have been determined by single crystal X-ray diffraction and characterized by Raman, IR, and optical spectroscopies.