9 research outputs found
Combination of Magnetic Susceptibility and Electron Paramagnetic Resonance to Monitor the 1D to 2D Solid State Transformation in Flexible MetalāOrganic Frameworks of Co(II) and Zn(II) with 1,4-Bis(triazol-1-ylmethyl)benzene
Two families of coordination polymers, {[MĀ(btix)<sub>2</sub>(OH<sub>2</sub>)<sub>2</sub>]Ā·2NO<sub>3</sub>Ā·2H<sub>2</sub>O}<sub><i>n</i></sub> [M = Co (<b>1</b>),
Zn (<b>2</b>), CoāZn (<b>3</b>); btix = 1,4-bisĀ(triazol-1-ylmethyl)Ābenzene]
and {[MĀ(btix)<sub>2</sub>(NO<sub>3</sub>)<sub>2</sub>]}<sub><i>n</i></sub> [M = Co (<b>4</b>), Zn (<b>5</b>), CoāZn
(<b>6</b>)], have been synthesized and characterized. The two
conformations of the ligand, <i>syn</i> and <i>anti</i>, lead to one-dimensional (1D) cationic chains or two-dimensional
(2D) neutral grids. Extrusion of the water molecules of the 1D compounds
results in an irreversible transformation into the 2D compounds, which
involves a change in conformation of the btix ligands and a rearrangement
in the metal environment with cleavage and reformation of covalent
bonds. This structural transformation has been followed by electron
paramagnetic resonance (EPR) and magnetic susceptibility measurements
to monitor the minor modifications that the metal centers suffer
Combination of Magnetic Susceptibility and Electron Paramagnetic Resonance to Monitor the 1D to 2D Solid State Transformation in Flexible MetalāOrganic Frameworks of Co(II) and Zn(II) with 1,4-Bis(triazol-1-ylmethyl)benzene
Two families of coordination polymers, {[MĀ(btix)<sub>2</sub>(OH<sub>2</sub>)<sub>2</sub>]Ā·2NO<sub>3</sub>Ā·2H<sub>2</sub>O}<sub><i>n</i></sub> [M = Co (<b>1</b>),
Zn (<b>2</b>), CoāZn (<b>3</b>); btix = 1,4-bisĀ(triazol-1-ylmethyl)Ābenzene]
and {[MĀ(btix)<sub>2</sub>(NO<sub>3</sub>)<sub>2</sub>]}<sub><i>n</i></sub> [M = Co (<b>4</b>), Zn (<b>5</b>), CoāZn
(<b>6</b>)], have been synthesized and characterized. The two
conformations of the ligand, <i>syn</i> and <i>anti</i>, lead to one-dimensional (1D) cationic chains or two-dimensional
(2D) neutral grids. Extrusion of the water molecules of the 1D compounds
results in an irreversible transformation into the 2D compounds, which
involves a change in conformation of the btix ligands and a rearrangement
in the metal environment with cleavage and reformation of covalent
bonds. This structural transformation has been followed by electron
paramagnetic resonance (EPR) and magnetic susceptibility measurements
to monitor the minor modifications that the metal centers suffer
Solvent-Free Synthesis of a Pillared Three-Dimensional Coordination Polymer with Magnetic Ordering
A new
magnetic coordination polymer, [FeĀ(bipy)Ā(im)<sub>2</sub>] (bipy =
4,4-bipyridine and im = imidazole), has been synthesized in a solvent-free
reaction. Structural analysis reveals a pillared 3D coordination polymer
composed by neutral layers, formed by ironĀ(II) and imidazolate linkers,
interconnected by bipy ligands which serve as pillars. Magnetic measurements
show that the material magnetically orders at low temperatures (<i>T</i><sub>c</sub> = 14.5 K) as a weak ferromagnet, likely due
to a spin canting
A Mixed-Ligand Approach for Spin-Crossover Modulation in a Linear Fe<sup>II</sup> Coordination Polymer
In
this work, we present a family of Fe<sup>II</sup> coordination polymers
of general formula [FeĀ(btzx)<sub>3ā3<i>x</i></sub>(btix)<sub>3<i>x</i></sub>]Ā(ClO<sub>4</sub>)<sub>2</sub> with interesting spin-crossover properties. These coordination polymers
have been synthesized using chemical mixtures of two different but
closely related ligands, 1,4-bisĀ(tetrazol-1-ylmethyl)Ābenzene (btzx)
and 1,4-bisĀ(triazol-1-ylmethyl)Ābenzene (btix), and the effect of a
gradual substitution of the ligand in the spin transition temperature
has been investigated. Several chemical mixtures have been structurally
characterized by X-ray powder diffraction indicating a clear critical
amount in the composition of the mixture after which mixed phases
rather than a single phase comprising mixed components are observed.
Importantly, this approach causes the appearance of a new transition
at lower temperatures that is not present in the pure [FeĀ(L)<sub>3</sub>]Ā(ClO<sub>4</sub>)<sub>2</sub> systems
Dynamic Magnetic Materials Based on the Cationic Coordination Polymer [Cu(btix)<sub>2</sub>]<sub><i>n</i></sub><sup>2<i>n</i>+</sup> [btix = 1,4-Bis(triazol-1-ylmethyl)benzene]: Tuning the Structural and Magnetic Properties through Anion Exchange
A three-dimensional coordination polymer, [CuĀ(btix)<sub>2</sub>(BF<sub>4</sub>)<sub>2</sub>]<sub><i>n</i></sub> [btix
= 1,4-bisĀ(triazol-1-ylmethyl)Ābenzene], with antiferromagnetic interactions
occurring via the organic ligand, has been prepared and characterized.
It has been shown to permit the exchange of anionic species in the
crystalline network with modification of the magnetic properties.
Coordinated BF<sub>4</sub><sup>ā</sup> can be reversibly exchanged
by different anions with (NO<sub>3</sub><sup>ā</sup> and Cl<sup>ā</sup>) or without (PF<sub>6</sub><sup>ā</sup> and
ClO<sub>4</sub><sup>ā</sup>) dynamic response of the organic
ligand, which acts as the only linker between the metal centers. Interestingly,
an irreversible exchange occurs with N<sub>3</sub><sup>ā</sup> anions to generate a new coordination polymer, [CuĀ(btix)Ā(N<sub>3</sub>)<sub>2</sub>]<sub><i>n</i></sub>, whose structure has
been determined ab initio by powder X-ray diffraction, revealing a
totally different connectivity between the Cu<sup>II</sup> centers.
These structural transformations are accompanied by a change of the
magnetic properties, which have been detected by electron paramagnetic
resonance and magnetic susceptibility measurements
Spin-Crossover Modification through Selective CO<sub>2</sub> Sorption
We
present a spin-crossover Fe<sup>II</sup> coordination polymer
with no permanent channels that selectively sorbs CO<sub>2</sub> over
N<sub>2</sub>. The one-dimensional chains display internal voids of
ā¼9 Ć
diameter, each being capable to accept one molecule
of CO<sub>2</sub> at 1 bar and 273 K. X-ray diffraction provides direct
structural evidence of the location of the gas molecules and reveals
the formation of Oī»Cī»OĀ(Ī“<sup>ā</sup>)Ā·Ā·Ā·Ļ
interactions. This physisorption modifies the spin transition, producing
a 9 K increase in <i>T</i><sub>1/2</sub>
Spin-Crossover Modification through Selective CO<sub>2</sub> Sorption
We
present a spin-crossover Fe<sup>II</sup> coordination polymer
with no permanent channels that selectively sorbs CO<sub>2</sub> over
N<sub>2</sub>. The one-dimensional chains display internal voids of
ā¼9 Ć
diameter, each being capable to accept one molecule
of CO<sub>2</sub> at 1 bar and 273 K. X-ray diffraction provides direct
structural evidence of the location of the gas molecules and reveals
the formation of Oī»Cī»OĀ(Ī“<sup>ā</sup>)Ā·Ā·Ā·Ļ
interactions. This physisorption modifies the spin transition, producing
a 9 K increase in <i>T</i><sub>1/2</sub>
Spin-Crossover Modification through Selective CO<sub>2</sub> Sorption
We
present a spin-crossover Fe<sup>II</sup> coordination polymer
with no permanent channels that selectively sorbs CO<sub>2</sub> over
N<sub>2</sub>. The one-dimensional chains display internal voids of
ā¼9 Ć
diameter, each being capable to accept one molecule
of CO<sub>2</sub> at 1 bar and 273 K. X-ray diffraction provides direct
structural evidence of the location of the gas molecules and reveals
the formation of Oī»Cī»OĀ(Ī“<sup>ā</sup>)Ā·Ā·Ā·Ļ
interactions. This physisorption modifies the spin transition, producing
a 9 K increase in <i>T</i><sub>1/2</sub>
Hybrid Magnetic Superconductors Formed by TaS<sub>2</sub> Layers and Spin Crossover Complexes
The restacking of charged TaS<sub>2</sub> nanosheets with molecular counterparts has so far allowed
for the combination of superconductivity with a manifold of other
molecule-intrinsic properties. Yet, a hybrid compound that blends
superconductivity with spin crossover switching has still not been
reported. Here we continue to exploit the solid-state/molecule-based
hybrid approach for the synthesis of a layered TaS<sub>2</sub>-based
material that hosts Fe<sup>2+</sup> complexes with a spin switching
behavior. The chemical design and synthetic aspects of the exfoliation/restacking
approach are discussed, highlighting how the material can be conveniently
obtained in the form of highly oriented easy-to-handle flakes. Finally,
proof of the presence of both phenomena is provided by the use of
a variety of physical characterization techniques. The likely sensitivity
of the intercalated Fe<sup>2+</sup> complexes to external stimuli
such as light opens the door for the study of synergistic effects
between the superconductivity and the spin crossover switching at
low temperatures