11 research outputs found
Unusual Intermolecular âThrough-Spaceâ <i>J</i> Couplings in PâSe Heterocycles
Solid-state NMR spectra
of new PâSe heterocycles based on <i>peri</i>-substituted
naphthalene motifs show the presence of
unusual <i>J</i> couplings between Se and P. These couplings
are between atoms in adjacent molecules and occur âthrough
spaceâ, rather than through conventional covalent bonds. Experimental
measurements are supported by relativistic DFT calculations, which
confirm the presence of couplings between nonbonded atoms, and provide
information on the pathway of the interaction. This observation improves
the understanding of <i>J</i> couplings and offers insight
into the factors that affect crystal packing in solids, for future
synthetic exploitation
Unusual Intermolecular âThrough-Spaceâ <i>J</i> Couplings in PâSe Heterocycles
Solid-state NMR spectra
of new PâSe heterocycles based on <i>peri</i>-substituted
naphthalene motifs show the presence of
unusual <i>J</i> couplings between Se and P. These couplings
are between atoms in adjacent molecules and occur âthrough
spaceâ, rather than through conventional covalent bonds. Experimental
measurements are supported by relativistic DFT calculations, which
confirm the presence of couplings between nonbonded atoms, and provide
information on the pathway of the interaction. This observation improves
the understanding of <i>J</i> couplings and offers insight
into the factors that affect crystal packing in solids, for future
synthetic exploitation
Solid-State Chemistry Shuffling of Alkali Ions toward New Layered Oxide Materials
Alkali transition-metal layered compounds usually contain
only
one type of alkali cation between the edge-shared octahedra layers.
Herein, the ternary phase diagram A2Ni2TeO6 (A = Li, Na, K) was explored through solid-state synthesis
and new alkali-mixed compositions showing alternation of distinct
alkali layers are obtained. Such intergrowth structures are synthesized
either by a single high-temperature treatment from raw chemicals or
through reaction between layered precursors, the latter involving
a solid-state process triggered at moderate temperatures. The in-depth
characterization of the multiple cationic orderings is performed by
combining powder diffraction techniques (X-rays and neutrons), high-resolution
transmission electron microscopy, and solid-state NMR spectroscopy.
In addition to the Ni/Te honeycomb ordering, alternation of lithium
layers with sodium or potassium layers is observed for compositions
(Li/Na)2Ni2TeO6 or (Li/K)2Ni2TeO6, respectively. Crystal structure solving
was achieved by stacking building blocks of the respective single
alkali layered oxides and unveiled a complex out-of-plane ordering
of honeycomb layers. Moreover, a solid-state reaction between Li2Ni2TeO6 and NaKNi2TeO6 enables preparation of the new phase Liâź1Naâź0.5Kâź0.5Ni2TeO6, a unique example containing up to three alkali cations and
exhibiting a more complex stacking with sodium and potassium cations
occupying the same layer. This investigation confirms that the chemical
versatility of layered alkali transition-metal compounds could also
occur on the alkali layer. Following the research methodology described
here, we revisit the crystal chemistry of alkali transition-metal
layered materials by exploring alkali ion substitutions previously
thought infeasible, in order to find new alkali-mixed compositions
Solid-State Chemistry Shuffling of Alkali Ions toward New Layered Oxide Materials
Alkali transition-metal layered compounds usually contain
only
one type of alkali cation between the edge-shared octahedra layers.
Herein, the ternary phase diagram A2Ni2TeO6 (A = Li, Na, K) was explored through solid-state synthesis
and new alkali-mixed compositions showing alternation of distinct
alkali layers are obtained. Such intergrowth structures are synthesized
either by a single high-temperature treatment from raw chemicals or
through reaction between layered precursors, the latter involving
a solid-state process triggered at moderate temperatures. The in-depth
characterization of the multiple cationic orderings is performed by
combining powder diffraction techniques (X-rays and neutrons), high-resolution
transmission electron microscopy, and solid-state NMR spectroscopy.
In addition to the Ni/Te honeycomb ordering, alternation of lithium
layers with sodium or potassium layers is observed for compositions
(Li/Na)2Ni2TeO6 or (Li/K)2Ni2TeO6, respectively. Crystal structure solving
was achieved by stacking building blocks of the respective single
alkali layered oxides and unveiled a complex out-of-plane ordering
of honeycomb layers. Moreover, a solid-state reaction between Li2Ni2TeO6 and NaKNi2TeO6 enables preparation of the new phase Liâź1Naâź0.5Kâź0.5Ni2TeO6, a unique example containing up to three alkali cations and
exhibiting a more complex stacking with sodium and potassium cations
occupying the same layer. This investigation confirms that the chemical
versatility of layered alkali transition-metal compounds could also
occur on the alkali layer. Following the research methodology described
here, we revisit the crystal chemistry of alkali transition-metal
layered materials by exploring alkali ion substitutions previously
thought infeasible, in order to find new alkali-mixed compositions
Solid-State Chemistry Shuffling of Alkali Ions toward New Layered Oxide Materials
Alkali transition-metal layered compounds usually contain
only
one type of alkali cation between the edge-shared octahedra layers.
Herein, the ternary phase diagram A2Ni2TeO6 (A = Li, Na, K) was explored through solid-state synthesis
and new alkali-mixed compositions showing alternation of distinct
alkali layers are obtained. Such intergrowth structures are synthesized
either by a single high-temperature treatment from raw chemicals or
through reaction between layered precursors, the latter involving
a solid-state process triggered at moderate temperatures. The in-depth
characterization of the multiple cationic orderings is performed by
combining powder diffraction techniques (X-rays and neutrons), high-resolution
transmission electron microscopy, and solid-state NMR spectroscopy.
In addition to the Ni/Te honeycomb ordering, alternation of lithium
layers with sodium or potassium layers is observed for compositions
(Li/Na)2Ni2TeO6 or (Li/K)2Ni2TeO6, respectively. Crystal structure solving
was achieved by stacking building blocks of the respective single
alkali layered oxides and unveiled a complex out-of-plane ordering
of honeycomb layers. Moreover, a solid-state reaction between Li2Ni2TeO6 and NaKNi2TeO6 enables preparation of the new phase Liâź1Naâź0.5Kâź0.5Ni2TeO6, a unique example containing up to three alkali cations and
exhibiting a more complex stacking with sodium and potassium cations
occupying the same layer. This investigation confirms that the chemical
versatility of layered alkali transition-metal compounds could also
occur on the alkali layer. Following the research methodology described
here, we revisit the crystal chemistry of alkali transition-metal
layered materials by exploring alkali ion substitutions previously
thought infeasible, in order to find new alkali-mixed compositions
Understanding the Formation Mechanisms of Silicon Particles from the Thermal Disproportionation of Hydrogen Silsesquioxane
Crystalline silicon
particles sustaining Mie resonances are readily
obtained from the thermal processing of hydrogen silsesquioxane (HSQ).
Here, the mechanisms involved in silicon particle formation and growth
from HSQ are investigated through real-time in situ analysis using an environmental transmission electron microscope
and X-ray diffractometer. The nucleation of Si nanodomains is observed
starting around 1000 °C. For the first time, a highly mobile
intermediate phase is experimentally observed, thus demonstrating
a previously unknown growth mechanism. At least two growth processes
occur simultaneously: the coalescence of small particles into larger
particles and growth mode by particle displacement through the matrix
toward the HSQ grain surface. Postsynthetic characterization by scanning
electron microscopy further supports the latter growth mechanism.
The gaseous environment employed during synthesis impacts particle
formation and growth under both in situ and ex situ conditions, impacting the particle yield and structural
homogeneity. Understanding the formation mechanisms of particles provides
promising pathways for reducing the energy cost of this synthetic
route
Understanding the Formation Mechanisms of Silicon Particles from the Thermal Disproportionation of Hydrogen Silsesquioxane
Crystalline silicon
particles sustaining Mie resonances are readily
obtained from the thermal processing of hydrogen silsesquioxane (HSQ).
Here, the mechanisms involved in silicon particle formation and growth
from HSQ are investigated through real-time in situ analysis using an environmental transmission electron microscope
and X-ray diffractometer. The nucleation of Si nanodomains is observed
starting around 1000 °C. For the first time, a highly mobile
intermediate phase is experimentally observed, thus demonstrating
a previously unknown growth mechanism. At least two growth processes
occur simultaneously: the coalescence of small particles into larger
particles and growth mode by particle displacement through the matrix
toward the HSQ grain surface. Postsynthetic characterization by scanning
electron microscopy further supports the latter growth mechanism.
The gaseous environment employed during synthesis impacts particle
formation and growth under both in situ and ex situ conditions, impacting the particle yield and structural
homogeneity. Understanding the formation mechanisms of particles provides
promising pathways for reducing the energy cost of this synthetic
route
Understanding the Formation Mechanisms of Silicon Particles from the Thermal Disproportionation of Hydrogen Silsesquioxane
Crystalline silicon
particles sustaining Mie resonances are readily
obtained from the thermal processing of hydrogen silsesquioxane (HSQ).
Here, the mechanisms involved in silicon particle formation and growth
from HSQ are investigated through real-time in situ analysis using an environmental transmission electron microscope
and X-ray diffractometer. The nucleation of Si nanodomains is observed
starting around 1000 °C. For the first time, a highly mobile
intermediate phase is experimentally observed, thus demonstrating
a previously unknown growth mechanism. At least two growth processes
occur simultaneously: the coalescence of small particles into larger
particles and growth mode by particle displacement through the matrix
toward the HSQ grain surface. Postsynthetic characterization by scanning
electron microscopy further supports the latter growth mechanism.
The gaseous environment employed during synthesis impacts particle
formation and growth under both in situ and ex situ conditions, impacting the particle yield and structural
homogeneity. Understanding the formation mechanisms of particles provides
promising pathways for reducing the energy cost of this synthetic
route
Understanding the Formation Mechanisms of Silicon Particles from the Thermal Disproportionation of Hydrogen Silsesquioxane
Crystalline silicon
particles sustaining Mie resonances are readily
obtained from the thermal processing of hydrogen silsesquioxane (HSQ).
Here, the mechanisms involved in silicon particle formation and growth
from HSQ are investigated through real-time in situ analysis using an environmental transmission electron microscope
and X-ray diffractometer. The nucleation of Si nanodomains is observed
starting around 1000 °C. For the first time, a highly mobile
intermediate phase is experimentally observed, thus demonstrating
a previously unknown growth mechanism. At least two growth processes
occur simultaneously: the coalescence of small particles into larger
particles and growth mode by particle displacement through the matrix
toward the HSQ grain surface. Postsynthetic characterization by scanning
electron microscopy further supports the latter growth mechanism.
The gaseous environment employed during synthesis impacts particle
formation and growth under both in situ and ex situ conditions, impacting the particle yield and structural
homogeneity. Understanding the formation mechanisms of particles provides
promising pathways for reducing the energy cost of this synthetic
route
<i>Peri</i>-Substituted PhosphorusâTellurium SystemsâAn Experimental and Theoretical Investigation of the P¡¡¡Te through-Space Interaction
A series
of <i>peri</i>-substituted phosphorusâtellurium
systems Râ˛TeâAcenapâPR<sub>2</sub> (Râ˛
= Ph, <i>p</i>-An, Nap, Mes, Tip; Acenap = acenaphthene-5,6-diyl
(âC<sub>12</sub>H<sub>8</sub>); R = <sup><i>i</i></sup>Pr, Ph) exhibiting large âthrough-spaceâ spinâspin
coupling constants and the âonsetâ of three-center four-electron
type interactions is presented. The influence of the substituents
at the phosphorus and tellurium atoms as well as their behavior upon
oxidation (with S, Se) or metal-coordination (Pt, Au) is discussed
using NMR spectroscopy, single-crystal X-ray diffraction, and advanced
density functional theory studies including NBO, AIM, and ELI-D analyses