Thermochromism, the Alexandrite Effect, and Dynamic Jahn–Teller Distortions in Ho₂Cu(TeO₃)₂(SO₄)₂

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. Magnetic studies reveal an effective magnetic moment of 14.97 μB. which has a good agreement with the calculated value of 15.09 μB

Thermochromism, the Alexandrite Effect, and Dynamic Jahn–Teller Distortions in Ho₂Cu(TeO₃)₂(SO₄)₂

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. Magnetic studies reveal an effective magnetic moment of 14.97 μB. which has a good agreement with the calculated value of 15.09 μB

Synthesis and Spectroscopy of New Plutonium(III) and -(IV) Molybdates: Comparisons of Electronic Characteristics

Synthesis of a plutonium­(III) molybdate bromide, PuMoO₄Br­(H₂O), has been accomplished using hydrothermal techniques in an inert-atmosphere glovebox. The compound is green in color, which is in stark contrast to the typical blue color of plutonium­(III) complexes. The unusual color arises from the broad charge transfer (CT) spanning from approximately 300 to 500 nm in the UV–vis–near-IR spectra. Repeating the synthesis with an increase in the reaction temperature results in the formation of a plutonium­(IV) molybdate, Pu₃Mo₆O₂₄(H₂O)₂, which also has a broad CT band and red-shifted f–f transitions. Performing an analogous reaction with neodymium produced a completely different product, [Nd­(H₂O)₃]­[NdMo₁₂O₄₂]·2H₂O, which is built of Silverton-type polyoxometallate clusters

Expansion of the Rich Structures and Magnetic Properties of Neptunium Selenites: Soft Ferromagnetism in Np(SeO₃)₂

Two new neptunium selenites with different oxidation states of the metal centers, Np^IV(SeO₃)₂ and Np^VIO₂(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 <i>P</i>2₁/<i>n</i>, <i>a</i> = 7.0089(5) Å, <i>b</i> = 10.5827(8) Å, <i>c</i> = 7.3316(5) Å, β = 106.953(1)°); whereas NpO₂(SeO₃) crystals are garnet-colored with an acicular habit (space group <i>P</i>2₁/<i>m</i>, <i>a</i> = 4.2501(3) Å, <i>b</i> = 9.2223(7) Å, <i>c</i> = 5.3840(4) Å, β = 90.043(2)°). Single-crystal X-ray diffraction studies reveal that the structure of Np­(SeO₃)₂ features a three-dimensional (3D) framework consisting of edge-sharing NpO₈ units that form chains that are linked via SeO₃ units to create a 3D framework. NpO₂(SeO₃) possesses a lamellar structure in which each layer is composed of NpO₈ hexagonal bipyramids bridged via SeO₃^2– anions. Bond-valence sum calculations and UV-vis-NIR absorption spectra support the assignment of tetravalent and hexavalent states of neptunium in Np­(SeO₃)₂ and NpO₂(SeO₃), respectively. Magnetic susceptibility data for Np­(SeO₃)₂ deviates substantially from typical Curie–Weiss behavior, which can be explained by large temperature-independent paramagnetic (TIP) effects. The Np^IV selenite shows weak ferromagnetic ordering at 3.1(1) K with no detectable hysteresis, suggesting soft ferromagnetic behavior

Synthesis and Spectroscopy of New Plutonium(III) and -(IV) Molybdates: Comparisons of Electronic Characteristics

Synthesis of a plutonium­(III) molybdate bromide, PuMoO₄Br­(H₂O), has been accomplished using hydrothermal techniques in an inert-atmosphere glovebox. The compound is green in color, which is in stark contrast to the typical blue color of plutonium­(III) complexes. The unusual color arises from the broad charge transfer (CT) spanning from approximately 300 to 500 nm in the UV–vis–near-IR spectra. Repeating the synthesis with an increase in the reaction temperature results in the formation of a plutonium­(IV) molybdate, Pu₃Mo₆O₂₄(H₂O)₂, which also has a broad CT band and red-shifted f–f transitions. Performing an analogous reaction with neodymium produced a completely different product, [Nd­(H₂O)₃]­[NdMo₁₂O₄₂]·2H₂O, which is built of Silverton-type polyoxometallate clusters

LnV₃Te₃O₁₅(OH)₃·<i>n</i>H₂O (Ln = Ce, Pr, Nd, Sm, Eu, Gd; <i>n</i> = 1–2): A New Series of Semiconductors with Mixed-Valent Tellurium (IV,VI) Oxoanions

Six new lanthanide tellurium vanadates with the general formula LnV₃Te₃O₁₅(OH)₃·<i>n</i>H₂O (<b>LnVTeO</b>) (Ln = Ce, Pr, Nd, Sm, Eu, and Gd; <i>n</i> = 2 for Ce and Pr; <i>n</i> = 1 for Nd, Sm, Eu, and Gd) have been prepared hydrothermally via the reactions of lanthanide nitrates, TeO₂, and V₂O₅ at 230 °C. <b>LnVTeO</b> adopts a three-dimensional (3D) channel structure with a space group of <i>P</i>6₃/<i>mmc</i>. Surprisingly, two types of oxoanions: Te^IVO₃^2– trigonal pyramids and Te^VIO₆^6– octahedra, coexist in these compounds. Solid-state UV–vis–NIR absorption spectra for <b>LnVTeO</b> show approximate band gaps on the order of 1.9 eV, suggesting the wide band gap semiconducting nature of these materials. No magnetic phase transition was observed in any of the analogues, but a clear increase in the strength of short-range antiferromagnetic correlations was found with the shortening of distances between magnetically coupled Ln³⁺ ions in <b>LnVTeO</b>

Effect of pH and Reaction Time on the Structures of Early Lanthanide(III) Borate Perchlorates

Reactions of LnCl₃·6H₂O (Ln = La–Nd, Sm, Eu), concentrated (11 M) perchloric acid, and molten boric acid result in the formation of four different compounds. These compounds are Ln­[B₈O₁₀(OH)₆(H₂O)­(ClO₄)]·0.5H₂O (Ln = La–Nd, Sm), Pr­[B₈O₁₁(OH)₄(H₂O)­(ClO₄)], Ln­[B₇O₁₁(OH)­(H₂O)₂(ClO₄)] (Ln = Pr, Nd, Sm, and Eu), and Ce­[B₈O₁₁(OH)₄(H₂O)­(ClO₄)]. All Ln­(III) cations are ten-coordinate with a capped triangular cupola geometry and contain an inner-sphere, monodentate perchlorate moiety. This geometry is obtained because of the coordination of the oxygen donors within the polyborate sheet which create triangular holes and provide residence for the lanthanide metal centers. Aside from Ln­[B₈O₁₀(OH)₆(H₂O)­(ClO₄)]·0.5H₂O (Ln = La–Nd, Sm), which are two-dimensional sheet structures, all other compounds are three-dimensional frameworks in which the layers are tethered together by BO₃ units found roughly perpendicular to the sheets. Furthermore, a change in product is observed depending on the reaction duration while holding all other synthetic variables constant. This report also demonstrates that lanthanide borates can be prepared in extreme acidic conditions

LnV₃Te₃O₁₅(OH)₃·<i>n</i>H₂O (Ln = Ce, Pr, Nd, Sm, Eu, Gd; <i>n</i> = 1–2): A New Series of Semiconductors with Mixed-Valent Tellurium (IV,VI) Oxoanions

Six new lanthanide tellurium vanadates with the general formula LnV₃Te₃O₁₅(OH)₃·<i>n</i>H₂O (<b>LnVTeO</b>) (Ln = Ce, Pr, Nd, Sm, Eu, and Gd; <i>n</i> = 2 for Ce and Pr; <i>n</i> = 1 for Nd, Sm, Eu, and Gd) have been prepared hydrothermally via the reactions of lanthanide nitrates, TeO₂, and V₂O₅ at 230 °C. <b>LnVTeO</b> adopts a three-dimensional (3D) channel structure with a space group of <i>P</i>6₃/<i>mmc</i>. Surprisingly, two types of oxoanions: Te^IVO₃^2– trigonal pyramids and Te^VIO₆^6– octahedra, coexist in these compounds. Solid-state UV–vis–NIR absorption spectra for <b>LnVTeO</b> show approximate band gaps on the order of 1.9 eV, suggesting the wide band gap semiconducting nature of these materials. No magnetic phase transition was observed in any of the analogues, but a clear increase in the strength of short-range antiferromagnetic correlations was found with the shortening of distances between magnetically coupled Ln³⁺ ions in <b>LnVTeO</b>

Ionothermal Synthesis of Tetranuclear Borate Clusters Containing <i>f</i>- and <i>p</i>‑Block Metals

The reactions of simple oxides or halides of trivalent lanthanides and actinides or bismuth with boric acid in the ionic liquid 1-butyl-3-methyl­imid­azolium chloride at 150 °C result in the formation and crystallization of a series of isomorphous tetranuclear borate clusters with the general formula M₄B₂₂O₃₆(OH)₆(H₂O)₁₃ (M = La, Ce, Pr, Nd, Sm, Eu, Gd, Pu, and Bi). These clusters do not assemble with trivalent cations smaller than Gd³⁺, suggesting that the formation of the clusters is dictated by the size of the metal ion. The cations are found in cavities along the periphery of a cage assembled from the corner- and edge-sharing interactions of BO₃ triangles and BO₄ tetrahedra, yielding a complex chiral cluster. Both enantiomers cocrystallize. The metal ions are nonacoordinate, and their geometries are best described as distorted tridiminished icosahedra. This coordination environment is new for both Pu³⁺ and Bi³⁺. In addition to detailed structural information, UV/vis–NIR absorption and photoluminescence spectra are also provided

Effects of Large Halides on the Structures of Lanthanide(III) and Plutonium(III) Borates

Reactions of LnBr₃ or LnOI with molten boric acid result in formation of Ln­[B₅O₈(OH)­(H₂O)₂Br] (Ln = La–Pr), Nd₄[B₁₈O₂₅(OH)₁₃Br₃], or Ln­[B₅O₈(OH)­(H₂O)₂I] (Ln = La–Nd). Reaction of PuOI with molten boric acid yields Pu­[B₇O₁₁(OH)­(H₂O)₂I]. The Ln­(III) and Pu­(III) centers in these compounds are found as nine-coordinate hula-hoop or 10-coordinate capped triangular cupola geometries where there are six approximately coplanar oxygen donors provided by triangular holes in the polyborate sheets. The borate sheets are connected into three-dimensional networks by additional BO₃ triangles and/or BO₄ tetrahedra that are roughly perpendicular to the layers. The room-temperature absorption spectrum of single crystals of Pu­[B₇O₁₁(OH)­(H₂O)₂I] shows characteristic f–f transitions for Pu­(III) that are essentially indistinguishable from Pu­(III) in other compounds with alternative ligands and different coordination environments