4 research outputs found
Synthesis and Properties of Uranium Sulfide Cations. An Evaluation of the Stability of Thiouranyl, {SUS}<sup>2+</sup>
Atomic uranium cations, U<sup>+</sup> and U<sup>2+</sup>, 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 U<sup>2+</sup> resulted in US<sub>2</sub><sup>2+</sup>; density functional theory computations indicate that the ground-state
structure for this species is side-on η<sup>2</sup>-S<sub>2</sub> triangular US<sub>2</sub><sup>2+</sup>, with the linear thiouranyl
isomer, {SU<sup>VI</sup>S}<sup>2+</sup>, some 171
kJ mol<sup>–1</sup> 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<sub><i>x</i></sub>Dy<sub>8‑x</sub>(OH)<sub>20</sub>Cl<sub>4</sub>·6H<sub>2</sub>O: 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 = Dy<sub>8</sub>(OH)<sub>20</sub>Cl<sub>4</sub>·6H<sub>2</sub>O). 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 AnC<sub>4</sub> alloys (An = Th, U) yielded gas-phase molecular thorium and uranium
carbide cluster cations of composition An<sub><i>m</i></sub>C<sub><i>n</i></sub><sup>+</sup>, 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<sub><i>m</i></sub>C<sub><i>n</i></sub><sup>+</sup> cluster ions with <i>m</i> = 3–13 and <i>n</i> = 5–30 were also produced, with an intriguing high
intensity of Th<sub>13</sub>C<sub><i>n</i></sub><sup>+</sup> cations. The AnC<sub>13</sub><sup>+</sup> ions also exhibited an
unexpectedly high abundance, in contrast to the gradual decrease in
the intensity of other AnC<sub><i>n</i></sub><sup>+</sup> ions with increasing values of <i>n</i>. High abundances
of AnC<sub>2</sub><sup>+</sup> and AnC<sub>4</sub><sup>+</sup> ions
are consistent with enhanced stability due to strong metal–C<sub>2</sub> bonds. Among the most abundant bimetallic ions was Th<sub>2</sub>C<sub>3</sub><sup>+</sup> for thorium; in contrast, U<sub>2</sub>C<sub>4</sub><sup>+</sup> was the most intense bimetallic
for uranium, with essentially no U<sub>2</sub>C<sub>3</sub><sup>+</sup> 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 An<sub>2</sub>C<sub>3</sub><sup>+</sup> and An<sub>2</sub>C<sub>4</sub><sup>+</sup> cluster ions, which elucidate the observed differing abundances
of the bimetallic carbide ions. Particularly noteworthy is that the
Th atoms are essentially equivalent in Th<sub>2</sub>C<sub>3</sub><sup>+</sup>, whereas there is a large asymmetry between the U atoms
in U<sub>2</sub>C<sub>3</sub><sup>+</sup>