12 research outputs found
Pressure-Induced Magnetic Crossover Driven by Hydrogen Bonding in CuF2(H2O)2(3-chloropyridine)
Hydrogen bonding plays a foundational role in the life, earth, and chemical sciences, with its richness and strength depending on the situation. In molecular materials, these interactions determine assembly mechanisms, control superconductivity, and even permit magnetic exchange. In spite of its long-standing importance, exquisite control of hydrogen bonding in molecule-based magnets has only been realized in limited form and remains as one of the major challenges. Here, we report the discovery that pressure can tune the dimensionality of hydrogen bonding networks in CuF2(H2O)2(3-chloropyridine) to induce magnetic switching. Specifically, we reveal how the development of exchange pathways under compression combined with an enhanced ab-plane hydrogen bonding network yields a three dimensional superexchange web between copper centers that triggers a reversible magnetic crossover. Similar pressure- and strain-driven crossover mechanisms involving coordinated motion of hydrogen bond networks may play out in other quantum magnets
Light Switchable Magnetism in a Coordination Polymer Heterostructure Combining the Magnetic Potassium Chromiumhexacyanochromate with the Light-Responsive Rubidium Cobalthexacyanoferrate
Light Switchable Magnetism in a Coordination Polymer
Heterostructure Combining the Magnetic Potassium Chromiumhexacyanochromate
with the Light-Responsive Rubidium Cobalthexacyanoferrat
Light-induced changes in magnetism in a coordination polymer heterostructure, Rb0.24Co[Fe(CN)6][email protected][Cr(CN)6]0.70· n H2O and the role of the shell thickness on the properties of both core and shell
Particles of formula Rb0.24Co[Fe(CN)6][email protected][Cr(CN)6]0.70·nH2O with a light-responsive rubidium cobalt hexacyanoferrate (RbCoFe) core and a magnetic potassium cobalt hexacyanochromate (KCoCr) shell have been prepared and exhibit light-induced changes in the magnetization of the normally light-insensitive KCoCr shell, a new property resulting from the synergy between the core and shell of a coordination polymer heterostructure. A single batch of 135 ± 12 nm RbCoFe particles are used as seeds to generate three different core@shell samples, with KCoCr shell thicknesses of approximately 11, 23 and 37 nm, to probe the influence of the shell thickness over the particles morphology and structural and magnetic properties. Synchrotron powder X-ray diffraction reveals that structural changes in the shell accompany the charge transfer induced spin transition (CTIST) of the core, giving direct evidence that the photomagnetic response of the shell is magnetomechanical in origin. The depth to which the KCoCr shell contributes to changes in magnetization is estimated to be approximately 24 nm when using a model that assumes a constant magnetic response of the core within the series of particles. In turn, the presence of the shell changes the nature of the CTIST of the core. As opposed to the usually observed first order transition exhibiting hysteresis, the CTIST becomes continuous in the core@shell particles
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Magnetic-field-induced shift of the optical band gap in Ni3 V2 O8
Physical Review B - Condensed Matter and Materials Physics.
Volume 89, Issue 16, 17 April 2014, Article number 165120.We employ a magnetic-field driven antiferromagnetic to the fully polarized state transition in Ni3V2O8 to investigate the interaction between spin ordering and driven charge excitations, with special emphasis on the color properties. Our measurements reveal field-induced blue shifts of the band gap that are much larger than that of the Zeeman effect in isolation, anticipating a more greenish appearance in the fully polarized state. This color change is verified with direct photographic images and emanates from charge density differences around the Ni and O centers in high fields. © 2014 American Physical Society
Local Lattice Distortions in Mn[N(CN)<sub>2</sub>]<sub>2</sub> under Pressure
We combined synchrotron-based infrared
spectroscopy, Raman scattering, and diamond anvil cell techniques
with complementary lattice dynamics calculations to reveal local lattice
distortions in MnÂ[NÂ(CN)<sub>2</sub>]<sub>2</sub> under compression.
Strikingly, we found a series of transitions involving octahedral
counter-rotations, changes in the local Mn environment, and deformations
of the superexchange pathway. In addition to reinforcing magnetic
property trends, these pressure-induced local lattice distortions
may provide an avenue for the development of new functionalities
Light-Induced Changes in Magnetism in a Coordination Polymer Heterostructure, Rb<sub>0.24</sub>Co[Fe(CN)<sub>6</sub>]<sub>0.74</sub>@K<sub>0.10</sub>Co[Cr(CN)<sub>6</sub>]<sub>0.70</sub>·<i>n</i>H<sub>2</sub>O and the Role of the Shell Thickness on the Properties of Both Core and Shell
Particles
of formula Rb<sub>0.24</sub>CoÂ[FeÂ(CN)<sub>6</sub>]<sub>0.74</sub>@K<sub>0.10</sub>CoÂ[CrÂ(CN)<sub>6</sub>]<sub>0.70</sub>·<i>n</i>H<sub>2</sub>O with a light-responsive rubidium cobalt
hexacyanoferrate (RbCoFe) core and a magnetic potassium cobalt hexacyanochromate
(KCoCr) shell have been prepared and exhibit light-induced changes
in the magnetization of the normally light-insensitive KCoCr shell,
a new property resulting from the synergy between the core and shell
of a coordination polymer heterostructure. A single batch of 135 ±
12 nm RbCoFe particles are used as seeds to generate three different
core@shell samples, with KCoCr shell thicknesses of approximately
11, 23 and 37 nm, to probe the influence of the shell thickness over
the particles’ morphology and structural and magnetic properties.
Synchrotron powder X-ray diffraction reveals that structural changes
in the shell accompany the charge transfer induced spin transition
(CTIST) of the core, giving direct evidence that the photomagnetic
response of the shell is magnetomechanical in origin. The depth to
which the KCoCr shell contributes to changes in magnetization is estimated
to be approximately 24 nm when using a model that assumes a constant
magnetic response of the core within the series of particles. In turn,
the presence of the shell changes the nature of the CTIST of the core.
As opposed to the usually observed first order transition exhibiting
hysteresis, the CTIST becomes continuous in the core@shell particles
Synthesis, Characterization, and Investigation of the Antimicrobial Activity of Cetylpyridinium Tetrachlorozincate
Cetylpyridinium tetrachlorozincate (referred to herein as (CP)2ZnCl4) was synthesized and its solid-state structure was elucidated via single-crystal X-ray diffraction (SC-XRD), revealing a stoichiometry of C42H76Cl4N2Zn with two cetylpyridinium (CP) cations per [ZnCl4]2– tetrahedra. Crystal structures at 100 and 298 K exhibited a zig-zag pattern with alternating alkyl chains and zinc units. The material showed potential for application as a broad-spectrum antimicrobial agent, to reduce volatile sulfur compounds (VSCs) generated by bacteria, and in the fabrication of advanced functional materials. Minimum inhibitory concentration (MIC) of (CP)2ZnCl4 was 60, 6, and 6 μg mL–1 for Salmonella enterica, Staphylococcus aureus, and Streptococcus mutans, respectively. The MIC values of (CP)2ZnCl4 were comparable to that of pure cetylpyridinium chloride (CPC), despite the fact that approximately 16% of the bactericidal CPC is replaced with bacteriostatic ZnCl2 in the structure. A modified layer-by-layer deposition technique was implemented to synthesize mesoporous silica (i.e., SBA-15) loaded with approximately 9.0 wt % CPC and 8.9 wt % Zn
Synthesis, Characterization, and Investigation of the Antimicrobial Activity of Cetylpyridinium Tetrachlorozincate
Cetylpyridinium tetrachlorozincate (referred to herein as (CP)2ZnCl4) was synthesized and its solid-state structure was elucidated via single-crystal X-ray diffraction (SC-XRD), revealing a stoichiometry of C42H76Cl4N2Zn with two cetylpyridinium (CP) cations per [ZnCl4]2– tetrahedra. Crystal structures at 100 and 298 K exhibited a zig-zag pattern with alternating alkyl chains and zinc units. The material showed potential for application as a broad-spectrum antimicrobial agent, to reduce volatile sulfur compounds (VSCs) generated by bacteria, and in the fabrication of advanced functional materials. Minimum inhibitory concentration (MIC) of (CP)2ZnCl4 was 60, 6, and 6 μg mL–1 for Salmonella enterica, Staphylococcus aureus, and Streptococcus mutans, respectively. The MIC values of (CP)2ZnCl4 were comparable to that of pure cetylpyridinium chloride (CPC), despite the fact that approximately 16% of the bactericidal CPC is replaced with bacteriostatic ZnCl2 in the structure. A modified layer-by-layer deposition technique was implemented to synthesize mesoporous silica (i.e., SBA-15) loaded with approximately 9.0 wt % CPC and 8.9 wt % Zn
Light-Induced Magnetization Changes in a Coordination Polymer Heterostructure of a Prussian Blue Analogue and a Hofmann-like Fe(II) Spin Crossover Compound
Coordination polymer thin film heterostructures
of the Prussian
blue analogue Ni<sup>II</sup><sub><i>b</i></sub>[Cr<sup>III</sup>(CN)<sub>6</sub>]<sub>0.7</sub>·<i>n</i>H<sub>2</sub>O (NiCr-PBA) and the 3D Hofmann-like spin crossover compound
FeÂ(azpy)Â[PtÂ(CN)<sub>4</sub>]·<i>x</i>H<sub>2</sub>O
{azpy = 4,4′-azopyridine} have been developed, and spin transition
properties have been characterized via SQUID magnetometry and Raman
spectroscopy. The magnetic response of the ferromagnetic NiCr-PBA
layer (<i>T</i><sub>c</sub> ≈ 70 K) can be altered
by inducing the LIESST effect (light-induced excited spin state trapping)
in the coupled paramagnetic FeÂ(II) spin crossover material. Whereas
an increase in magnetization is measured for the single-phase FeÂ(azpy)Â[PtÂ(CN)<sub>4</sub>]·<i>x</i>H<sub>2</sub>O, a decrease in magnetization
is observed for the heterostructure. These results indicate the LIESST
effect alone cannot account for the sign and magnitude of the magnetization
change in the heterostructure, but the temperature profile of the
magnetization shows that significant changes in the NiCr-PBA network
are correlated to the spin state of the Hofmann-like SCO network