Publications by authors named "Kariem Diefenbach"

Radiation dosimeters displaying conspicuous response of irradiance are highly desirable, owing to the growing demand of monitoring high-energy radiation and environmental exposure. Herein, we present a case of dosimetry based on a discrete nanocluster, [Th(OH)(O)(HO)](TPC)(HCOO)∙4DMF∙HO (Th-SINAP-100), by judiciously incorporating heavy Th polynuclear centers as radiation attenuator and organic linkers as photo-responsive sensor. Interestingly, dual-module photochromic transitions upon multiple external stimuli including UV, β-ray, and γ-ray are integrated into this single material.

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The synthesis of a large family of heterobimetallic lanthanide copper sulfates was realized via stoichiometric hydrothermal reactions among LnO, CuO, and HSO, giving rise to four distinct phases, namely LnCu(SO)(OH) (Ln = Sm-Ho) (), LnCu(SO)(OH) (Ln = Tm-Lu) (), LnCu(SO)(OH) (Ln = Nd-Gd, except Pm) (), and LnCu(SO)(OH) (Ln = Dy-Lu) (), with completely different topologies. The passage from and to and across the 4f series, respectively, can be ascribed to the effect of lanthanide contraction, which progressively induces shrinking of the Ln-O distance, reduction in the Ln coordination number, and eventually structural transitions. The incorporation of identical 3d-4f metal ions into different spin-lattices, in conjunction with substitution of diverse Ln cations within the same spin-lattice, gives rise to tunable magnetic properties varying from ferromagnetic ordering in and to antiferromagnetic ordering in , and to paramagnetic correlations found in and .

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A unique selective crystallization strategy based on an iodate-sulfate mixed-anion system has been developed for lanthanide separation. Periodic divergences in crystal formation energy enable simple Nd/Dy, La/Lu, Gd/Tb, La/Dy, and Nd/Lu separations through crystallization of the early lanthanides, giving rise to separation factors up to 123(5), 100(2), 2.4(2), 137(9), and 85(6), respectively.

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Expanding the family of f-element bearing molybdate iodates via hydrothermal reactions has yielded ten new rare-earth molybdate iodates with two distinct phases, Ln(MoO2)(IO3)4(OH) (LnMoIO-1, Ln = Ce and Pr) and Ln(Mo2O7)(IO3)(H2O)2 (LnMoIO-2, Ln = Gd-Yb, and Y), as well as the first thorium molybdate iodate, ThF(MO4)(IO3) (ThFMoIO). All three structures exhibit three dimensional frameworks and are exclusively built from lanthanide/actinide polyhedra bridged by molybdates and iodates. Furthermore, the coordination versatility of molybdates (octahedral, square pyramidal, and tetrahedral geometries) results in a diversity of structures.

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A break in periodicity occurs in the actinide series between plutonium and americium as the result of the localization of 5f electrons. The subsequent chemistry of later actinides is thought to closely parallel lanthanides in that bonding is expected to be ionic and complexation should not substantially alter the electronic structure of the metal ions. Here we demonstrate that ligation of californium(III) by a pyridine derivative results in significant deviations in the properties of the resultant complex with respect to that predicted for the free ion.

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Six new lanthanide tellurium vanadates with the general formula LnV3Te3O15(OH)3·nH2O (LnVTeO) (Ln = Ce, Pr, Nd, Sm, Eu, and Gd; n = 2 for Ce and Pr; n = 1 for Nd, Sm, Eu, and Gd) have been prepared hydrothermally via the reactions of lanthanide nitrates, TeO2, and V2O5 at 230 °C. LnVTeO adopts a three-dimensional (3D) channel structure with a space group of P63/mmc. Surprisingly, two types of oxoanions: Te(IV)O3(2-) trigonal pyramids and Te(VI)O6(6-) octahedra, coexist in these compounds.

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Twenty-two new lanthanide tellurite sulfates with five distinct structures, Ln2(Te2O5)(SO4)2 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb; LnTeSO-1), Ho3(TeO3)2(SO4)2(OH)(H2O) (LnTeSO-2), Ln2TeO3(SO4)2(H2O)2 (Ln = Dy, Ho, Er; LnTeSO-3), Ln2(Te2O5)(SO4)2 (Ln = Er, Tm, Yb, Lu; LnTeSO-4), and Ln2(Te4O10)(SO4) (Ln = Gd, Dy, Ho, Er, Tm, Yb; LnTeSO-5), have been prepared and characterized. The topologies of LnTeSO-1, LnTeSO-2, LnTeSO-3, LnTeSO-4, and LnTeSO-5 are substantially different with respect to the connectivity between Ln polyhedra and the coordination environments of the lanthanide ions. For the first four topologies, the dimensionality changes from layered (LnTeSO-1) to chains (LnTeSO-2) to tetramers (LnTeSO-3) and finally to a monomer (LnTeSO-4).

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Two new neptunium selenites with different oxidation states of the metal centers, Np(IV)(SeO3)2 and Np(VI)O2(SeO3), have been synthesized under mild hydrothermal conditions at 200 °C from the reactions of NpO2 and SeO2. Np(SeO3)2 crystallizes as brown prisms (space group P21/n, a = 7.0089(5) Å, b = 10.

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The reaction of A2S3/U/P2S5/S at 500 °C affords the quinary U(IV) thiophosphates A6U3Sb2P8S32 (A = Rb, Cs). These compounds contain {U3(PS4)2[Sb(PS4)3]2}(6-) layers separated by alkali metal cations. The layers are composed of trimeric uranium units connected to each other by the thiophosphato-antimonite anion, [Sb(PS4)3](6-).

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A 3d-4f heterobimetallic material with mixed anions, Ho2Cu(TeO3)2(SO4)2, has been prepared under hydrothermal conditions. Ho2Cu(TeO3)2(SO4)2 exhibits both thermochromism and the Alexandrite effect. Variable temperature single crystal X-ray diffraction and UV-vis-NIR spectroscopy reveal that changes in the Cu(II) coordination geometry result in negative thermal expansion of axial Cu-O bonds that plays a role in the thermochromic transition of Ho2Cu(TeO3)2(SO4)2.

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