Synthesis and Properties of Uranium Sulfide Cations. An Evaluation of the Stability of Thiouranyl, {SUS}²⁺

Atomic uranium cations, U⁺ and U²⁺, reacted with the facile sulfur-atom donor OCS to produce several monopositive and dipositive uranium sulfide species containing up to four sulfur atoms. Sequential abstraction of two sulfur atoms by U²⁺ resulted in US₂²⁺; density functional theory computations indicate that the ground-state structure for this species is side-on η²-S₂ triangular US₂²⁺, with the linear thiouranyl isomer, {SU^VIS}²⁺, some 171 kJ mol^–1 higher in energy. The result that the linear thiouranyl structure is a local minimum at a moderate energy suggests that it should be feasible to stabilize this moiety in molecular compounds

Europium(III) Tetrakis(β-diketonate) Complex as an Ionic Liquid: A Calorimetric and Spectroscopic Study

An intrinsic photoluminescent ionic liquid based on europium­(III) tetrakis­(β-diketonate) complex with a tetraalkylphosphonium as counterion was synthesized. Calorimetric measurements showed a melting point at 63 °C, which allows the ionic liquid classification. When cooling the material from the liquid state, metastable supercooled ionic liquid is obtained, as seen from NMR spectroscopy as well. Eu­(III) photoluminescence is clearly observed while the absorption spectra of the ligand is dominant, showing the antenna effect. This was confirmed with submicrosecond time scale luminescence spectroscopy, where a rise of Eu­(III) emission is observed with the correspondent decay of the ligand excited state. Temperature effects in the photoluminescence are also shown, being prominent above the melting point where the intensity decreases with Arrhenius behavior. Eu­(III) luminescence decays also show features characteristic of energy migration between homologue Eu­(III) species. Solvent effects were also studied by NMR and Luminescence spectroscopies, highlighting that the nucleophilicity of organic solvents such as <i>n</i>-alcohols leads to a coordination with Eu­(III), which ultimately compromises the stability of the complex

Magnetic Properties of the Layered Lanthanide Hydroxide Series Y_<i>x</i>Dy_8‑x(OH)₂₀Cl₄·6H₂O: From Single Ion Magnets to 2D and 3D Interaction Effects

The magnetic properties of layered dysprosium hydroxides, both diluted in the diamagnetic yttrium analogous matrix (LYH:0.04Dy), and intercalated with 2,6-naphthalene dicarboxylate anions (LDyH-2,6-NDC), were studied and compared with the recently reported undiluted compound (LDyH = Dy₈(OH)₂₀Cl₄·6H₂O). The Y diluted compound reveals a single-molecule magnet (SMM) behavior of single Dy ions, with two distinct slow relaxation processes of the magnetization at low temperatures associated with the two main types of Dy sites, 8- and 9-fold coordinated. Only one relaxation process is observed in both undiluted LDyH and intercalated compounds as a consequence of dominant ferromagnetic Dy–Dy interactions, both intra- and interlayer. Semiempirical calculations using a radial effect charge (REC) model for the crystal field splitting of the Dy levels are used to explain data in terms of contributions from the different Dy sites. The dominant ferromagnetic interactions are explained in terms of orientations of easy magnetization axes obtained by REC calculations together with the sign of the superexchange expected from the Dy–O–Dy angles

Thorium and Uranium Carbide Cluster Cations in the Gas Phase: Similarities and Differences between Thorium and Uranium

Laser ionization of AnC₄ alloys (An = Th, U) yielded gas-phase molecular thorium and uranium carbide cluster cations of composition An_<i>m</i>C_<i>n</i>⁺, with <i>m</i> = 1, <i>n</i> = 2–14, and <i>m</i> = 2, <i>n</i> = 3–18, as detected by Fourier transform ion-cyclotron-resonance mass spectrometry. In the case of thorium, Th_<i>m</i>C_<i>n</i>⁺ cluster ions with <i>m</i> = 3–13 and <i>n</i> = 5–30 were also produced, with an intriguing high intensity of Th₁₃C_<i>n</i>⁺ cations. The AnC₁₃⁺ ions also exhibited an unexpectedly high abundance, in contrast to the gradual decrease in the intensity of other AnC_<i>n</i>⁺ ions with increasing values of <i>n</i>. High abundances of AnC₂⁺ and AnC₄⁺ ions are consistent with enhanced stability due to strong metal–C₂ bonds. Among the most abundant bimetallic ions was Th₂C₃⁺ for thorium; in contrast, U₂C₄⁺ was the most intense bimetallic for uranium, with essentially no U₂C₃⁺ appearing. Density functional theory computations were performed to illuminate this distinction between thorium and uranium. The computational results revealed structural and energetic disparities for the An₂C₃⁺ and An₂C₄⁺ cluster ions, which elucidate the observed differing abundances of the bimetallic carbide ions. Particularly noteworthy is that the Th atoms are essentially equivalent in Th₂C₃⁺, whereas there is a large asymmetry between the U atoms in U₂C₃⁺