4 research outputs found
Tetranuclear Lanthanide(III) Complexes in a Seesaw Geometry: Synthesis, Structure, and Magnetism
The reaction of 2-methoxy-6-(pyridin-2-ylhydrazonomethyl)phenol
(LH) with Ln(III) (Ln = Gd, Tb, Dy, Ho) salts in the presence of an
excess of triethylamine afforded [Gd<sub>4</sub>(L)<sub>4</sub>(μ<sub>4</sub>-OH)(μ<sub>3</sub>-OH)<sub>2</sub>(NO<sub>3</sub>)<sub>4</sub>]·(NO<sub>3</sub>)·4CH<sub>3</sub>CN·CH<sub>3</sub>OH·2H<sub>2</sub>O (<b>1</b>), [Tb<sub>4</sub>(L)<sub>4</sub>(μ<sub>4</sub>-OH)(μ<sub>3</sub>-OH)<sub>2</sub>(NO<sub>3</sub>)<sub>4</sub>]·(NO<sub>3</sub>)·4CH<sub>3</sub>CN·3H<sub>2</sub>O (<b>2</b>), [Dy<sub>4</sub>(L)<sub>4</sub>(μ<sub>4</sub>-OH)(μ<sub>3</sub>-OH)<sub>2</sub>(NO<sub>3</sub>)<sub>4</sub>]·(NO<sub>3</sub>)·6CH<sub>3</sub>CN·H<sub>2</sub>O (<b>3</b>), and [Ho<sub>4</sub>(L)<sub>4</sub>(μ<sub>4</sub>-OH)(μ-OH)<sub>2</sub>(NO<sub>3</sub>)<sub>4</sub>]·(NO<sub>3</sub>)·8CH<sub>3</sub>CN·3CH<sub>3</sub>OH·2H<sub>2</sub>O (<b>4</b>). All four complexes
contain a monocationic tetranuclear core with a unique <i>seesaw</i> topology. The tetranuclear assembly is formed through the coordination
of four [L]<sup>−</sup>, one μ<sub>4</sub>-OH, two μ<sub>3</sub>-OH, and four chelating nitrate ligands, with a charge-balancing
nitrate counteranion. Magnetic studies reveal a weak antiferromagnetic
coupling throughout the series. Compound <b>1</b> can be modeled
well with an isotropic exchange between all centers parametrized by <i>J</i> = −0.09 cm<sup>–1</sup>. Compound <b>3</b> exhibits slow magnetic relaxation at low temperatures
Tetranuclear Lanthanide(III) Complexes in a Seesaw Geometry: Synthesis, Structure, and Magnetism
The reaction of 2-methoxy-6-(pyridin-2-ylhydrazonomethyl)phenol
(LH) with Ln(III) (Ln = Gd, Tb, Dy, Ho) salts in the presence of an
excess of triethylamine afforded [Gd<sub>4</sub>(L)<sub>4</sub>(μ<sub>4</sub>-OH)(μ<sub>3</sub>-OH)<sub>2</sub>(NO<sub>3</sub>)<sub>4</sub>]·(NO<sub>3</sub>)·4CH<sub>3</sub>CN·CH<sub>3</sub>OH·2H<sub>2</sub>O (<b>1</b>), [Tb<sub>4</sub>(L)<sub>4</sub>(μ<sub>4</sub>-OH)(μ<sub>3</sub>-OH)<sub>2</sub>(NO<sub>3</sub>)<sub>4</sub>]·(NO<sub>3</sub>)·4CH<sub>3</sub>CN·3H<sub>2</sub>O (<b>2</b>), [Dy<sub>4</sub>(L)<sub>4</sub>(μ<sub>4</sub>-OH)(μ<sub>3</sub>-OH)<sub>2</sub>(NO<sub>3</sub>)<sub>4</sub>]·(NO<sub>3</sub>)·6CH<sub>3</sub>CN·H<sub>2</sub>O (<b>3</b>), and [Ho<sub>4</sub>(L)<sub>4</sub>(μ<sub>4</sub>-OH)(μ-OH)<sub>2</sub>(NO<sub>3</sub>)<sub>4</sub>]·(NO<sub>3</sub>)·8CH<sub>3</sub>CN·3CH<sub>3</sub>OH·2H<sub>2</sub>O (<b>4</b>). All four complexes
contain a monocationic tetranuclear core with a unique <i>seesaw</i> topology. The tetranuclear assembly is formed through the coordination
of four [L]<sup>−</sup>, one μ<sub>4</sub>-OH, two μ<sub>3</sub>-OH, and four chelating nitrate ligands, with a charge-balancing
nitrate counteranion. Magnetic studies reveal a weak antiferromagnetic
coupling throughout the series. Compound <b>1</b> can be modeled
well with an isotropic exchange between all centers parametrized by <i>J</i> = −0.09 cm<sup>–1</sup>. Compound <b>3</b> exhibits slow magnetic relaxation at low temperatures
On the Possibility of Magneto-Structural Correlations: Detailed Studies of Dinickel Carboxylate Complexes
A series
of water-bridged dinickel complexes of the general formula [Ni<sub>2</sub>(μ<sub>2</sub>-OH<sub>2</sub>)(μ<sub>2</sub>-O<sub>2</sub>C<sup><i>t</i></sup>Bu)<sub>2</sub>(O<sub>2</sub>C<sup><i>t</i></sup>Bu)<sub>2</sub>(L)(L′)] (L =
HO<sub>2</sub>C<sup><i>t</i></sup>Bu, L′ = HO<sub>2</sub>C<sup><i>t</i></sup>Bu (<b>1</b>), pyridine
(<b>2</b>), 3-methylpyridine (<b>4</b>); L = L′
= pyridine (<b>3</b>), 3-methylpyridine (<b>5</b>)) has
been synthesized and structurally characterized by X-ray crystallography.
The magnetic properties have been probed by magnetometry and EPR spectroscopy,
and detailed measurements show that the axial zero-field splitting, <i>D</i>, of the nickel(II) ions is on the same order as the isotropic
exchange interaction, <i>J</i>, between the nickel sites.
The isotropic exchange interaction can be related to the angle between
the nickel centers and the bridging water molecule, while the magnitude
of <i>D</i> can be related to the coordination sphere at
the nickel sites
Creating Binary Cu–Bi Compounds via High-Pressure Synthesis: A Combined Experimental and Theoretical Study
Exploration
beyond the known phase space of thermodynamically stable
compounds into the realm of metastable materials is a frontier of
materials chemistry. The application of high pressure in experiment
and theory provides a powerful vector by which to explore this uncharted
phase space, allowing discovery of complex new structures and bonding
in the solid state. We harnessed this approach for the Cu–Bi
system, where the realization of new phases offers potential for exotic
properties such as superconductivity. This potential is due to the
presence of bismuth, which, by virtue of its status as one of the
heaviest stable elements, forms a critical component in emergent materials
such as superconductors and topological insulators. To fully investigate
and understand the Cu–Bi system, we welded theoretical predictions
with experiment to probe the Cu–Bi system under high pressures.
By employing the powerful approach of in situ X-ray diffraction in
a laser-heated diamond anvil cell (LHDAC), we thoroughly explored
the high-pressure and high-temperature (high-<i>PT</i>)
phase space to gain insight into the formation of intermetallic compounds
at these conditions. We employed density functional theory (DFT) calculations
to calculate a pressure versus temperature phase diagram, which correctly
predicts that CuBi is stabilized at lower pressures than Cu<sub>11</sub>Bi<sub>7</sub>, and allows us to uncover the thermodynamic contributions
responsible for the stability of each phase. Detailed comparisons
between the NiAs structure type and the two high-pressure Cu–Bi
phases, Cu<sub>11</sub>Bi<sub>7</sub> and CuBi, reveal the preference
for elemental segregation within the Cu–Bi phases, and highlight
the unique channels and layers formed by ordered Cu vacancies. The
electron localization function from DFT calculations account for the
presence of these “voids” as a manifestation of the
lone pair orientation on the Bi atoms. Our study demonstrates the
power of joint experimental–computational work in exploring
the chemistry occurring at high-<i>PT</i> conditions. The
existence of multiple high-pressure-stabilized phases in the Cu–Bi
binary system, which can be readily identified with in situ techniques,
offers promise for other systems in which no ambient pressure phases
are known to exist