21 research outputs found
Air-Stable Cyclohexasulfur as Cocrystal
A new stable cyclohexasulfur (cyclo-S<sub>6</sub>) was
discovered
in the crystal of 3,5-diphenyl-1,2,4-dithiazol-1-ium (dpdti); dpdti
was synthesized via an oxidation reaction of thiobenzamide with iodine
in benzene, under reflux. Two kinds of crystal habitsīøbrick-shaped
(crystal-<b>A</b>) and needle-shaped (crystal-<b>B</b>)īøwere obtained following recrystallization from acetonitrile
solvent. Single-crystal structure analysis using synchrotron X-ray
radiation showed that both crystal-<b>A</b> and -<b>B</b> consist of a dpdti cation and an iodine anion. Furthermore, neutral
cyclo-S<sub>6</sub> molecules are present in crystal-<b>A</b> as cocrystals, enclosed by the dpdti cation and the iodide anion.
This is akin to cyclosulfur of <i>S</i><sub><i>n</i></sub> in zeolites and sodalities, suggesting a contribution to the
stabilization of cyclo-S<sub>6</sub> molecules. The results show that
crystal engineering of cocrystals may be used as a method to control
the stability and activity of sulfur, for improved utilization
Magnetic Sponge Behavior via Electronic State Modulations
A reversible
magnetic change in response to external stimuli is
a desired function of molecular magnetic materials. The magnetic change
induced by a change in the intrinsic spin is significant because the
magnetic change is inevitable and could become drastic. In this study,
we demonstrate a reversible magnetic change closely associated with
electronic state modulations, as well as structural modifications
realized by solvation/desolvation cycles of a magnetic sponge. The
compound was a D<sub>2</sub>A-type layered magnet, [{Ru<sub>2</sub>(O<sub>2</sub>CPh-2,3,5-Cl<sub>3</sub>)<sub>4</sub>}<sub>2</sub>(TCNQMe<sub>2</sub>)]Ā·4DCM (<b>1</b>; 2,3,5-Cl<sub>3</sub>PhCO<sub>2</sub><sup>ā</sup> = 2,3,5-trichlorobenzoate; TCNQMe<sub>2</sub> = 2,5-dimethyl-7,7,8,8-tetracyanoquinodimethane; DCM = dichloromethane),
where [Ru<sub>2</sub>(O<sub>2</sub>CPh-2,3,5-Cl<sub>3</sub>)<sub>4</sub>] ([Ru<sub>2</sub><sup>II,II</sup>]) is an electron donor (D) and
TCNQMe<sub>2</sub> is an electron acceptor (A). Compound <b>1</b> had a one-electron-transferred, charge-ordered state with a [{Ru<sub>2</sub><sup>II,II</sup>}āTCNQMe<sub>2</sub><sup>ā¢ā</sup>ā{Ru<sub>2</sub><sup>II,III</sup>}<sup>+</sup>] (1e-I) formula.
Strong intralayer antiferromagnetic couplings between [Ru<sub>2</sub><sup>II,II</sup>] with <i>S</i> = 1 or [Ru<sub>2</sub><sup>II,III</sup>]<sup>+</sup> with <i>S</i> = 3/2 and TCNQMe<sub>2</sub><sup>ā¢ā</sup> with <i>S</i> = 1/2,
as well as ferromagnetic interlayer interactions, induced long-range
ferrimagnetic ordering at <i>T</i><sub>c</sub> = 101 K.
Interstitial DCM molecules were located between layers, and these
were gradually eliminated under vacuum at 80 Ā°C to form a solvent-free
compound (<b>1-dry</b>) without loss of crystallinity. The electronic
state of <b>1-dry</b> thermally fluctuated and eventually provided
a charge-disproportionate disordered state, with a [{Ru<sub>2</sub>}<sup>0.5+</sup>āTCNQMe<sub>2</sub><sup>1.5ā</sup>ā{Ru<sub>2</sub><sup>II,III</sup>}<sup>+</sup>] (1.5e-I) formula as the ground
state. The <i>T</i><sub>c</sub> in <b>1-dry</b> was
34 K because of the presence of diamagnetic TCNQMe<sub>2</sub><sup>2ā</sup> in some parts of the framework. A large <i>T</i><sub>c</sub> variation with Ī<i>T</i><sub>c</sub> ā 70 K was switchable; switching was achieved by charge-state
modulations accompanied by subtle structural modifications in solvation/desolvation
treatments
Triply Stacked Heterogeneous Array of Porphyrins and Phthalocyanine through Stepwise Formation of a Fourfold Rotaxane and an Ionic Complex
We
report the preparation and crystal structure of a triply stacked
metal complex array in which a Cuāphthalocyanine is sandwiched
between different Cuāporphyrins. The discrete heterogeneous
assembly was prepared through formation of a fourfold rotaxane from
a tetradactyl porphyrin with alkylammonium moieties and a phthalocyanine
bearing four crown ethers and the subsequent formation of an ionic
complex between the fourfold rotaxane and a tetraanionic porphyrin.
The tetraanionic porphyrin, CuāTPPS<sup>4ā</sup>, is
selectively bound to the fourfold rotaxane through cooperative ĻāĻ
and ionic interactions. The crystal structure revealed the columnar
stacked array of the three planar building components in a precise
order and spatial arrangement that promote intermolecular electronic
communication
Variable-Rung Design for a Mixed-Valence Two-Legged Ladder System Situated in a Dimensional Crossover Region
Ladder systems situated in a crossover
from one dimensionality to two dimensionalities have been an attractive
research target, because the physical properties, which are associated
with dimensionality, are strongly dependent on the number of constituent
legs. However, control of the intraladder configuration and electronic
properties based on the substitution of structural components remain
challenging tasks in materials science. On the other hand, structural
design using coordination chemistry offers crucial advantages for
architectural and electronic variations through substitutions of metalāorganic
building blocks. Here, we show the rational design and electronic
properties of novel metal complex-based two-legged ladder compounds
with several organic rung units: 4,4ā²-bipyridine, trans-1,4-diaminocyclohexane,
and 4,4ā²-azopyridine. Single-crystal X-ray studies show that
these two-legged ladder compounds are composed of halogen-bridged
mixed-valence one-dimensional chains (MX chains) as their constituent
legs. Depending on the molecular shape of the organic rung units,
unique configurations of two-legged ladder lattices with periodic
distortion of the legs are achieved. In addition, the electronic absorption
spectra show that intervalence charge-transfer (IVCT) band gap of
the two-legged ladder system increases with increasing degree of distortion
of the leg. We have demonstrated for the first time that a two-legged
ladder system shows a unique relationship between IVCT energy and
the distortion parameter of the leg, as distinct from a single MX
chain system. These systematic investigations, not only of configurations
based on the rung variation but also of electronic states in metalāorganic
ladder system, provide the possibility for wide and rational tunings
of physical and electronic properties of metal complex-based functional
materials
Neutral-Type One-Dimensional Mixed-Valence Halogen-Bridged Platinum Chain Complexes with Large Charge-Transfer Band Gaps
One-dimensional (1D) electronic systems
have attracted significant attention for a long time because of their
various physical properties. Among 1D electronic systems, 1D halogen-bridged
mixed-valence transition-metal complexes (the so-called MX chains)
have been thoroughly studied owing to designable structures and electronic
states. Here, we report the syntheses, structures, and electronic
properties of three kinds of novel neutral MX-chain complexes. The
crystal structures consist of 1D chains of PtāX repeating units
with (1<i>R</i>,2<i>R</i>)-(ā)-diaminocychlohexane
and CN<sup>ā</sup> in-plane ligands. Because of the absence
of a counteranion, the neutral MX chains have short interchain distances,
so that strong interchain electronic interaction is expected. Resonance
Raman spectra and diffuse-reflectance UVāvis spectra indicate
that their electronic states are mixed-valence states (charge-density-wave
state: Pt<sup>2+</sup>Ā·Ā·Ā·XāPt<sup>4+</sup>āXĀ·Ā·Ā·Pt<sup>2+</sup>Ā·Ā·Ā·XāPt<sup>4+</sup>āXĀ·Ā·Ā·).
In addition, the relationship between the intervalence charge-transfer
(IVCT) band gap and the degree of distortion of the 1D chain shows
that the neutral MX chains have a larger IVCT band gap than that of
cationic MX-chain complexes. These results provide new insight into
the physical and electronic properties of 1D chain compounds
Porous Coordination Polymer Polymorphs with Different Flexible Pores Using a Structurally Flexible and Bent 1,3-Bis(4-pyridyl)propane Ligand
Porous
coordination polymer (PCP) polymorphs with the formula [CuĀ(CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>(bpp)<sub>2</sub>]<sub><i>n</i></sub> [<b>1</b> and <b>2</b>, where bpp =
1,3-bisĀ(4-pyridyl)Āpropane] have been synthesized and crystallographically
characterized, and their distinguishable porous properties have been
investigated. <b>1</b> was obtained by the removal of guest
acetone molecules from one-dimensional PCP {[CuĀ(CF<sub>3</sub>SO<sub>3</sub>)Ā(bpp)<sub>2</sub>]Ā·CF<sub>3</sub>SO<sub>3</sub>Ā·2acetone}<sub><i>n</i></sub> (<b>1</b>ā2acetone), while <b>2</b> was derived from two-dimensional PCP {[CuĀ(CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>(bpp)<sub>2</sub>]Ā·H<sub>2</sub>O}<sub><i>n</i></sub> (<b>2</b>āH<sub>2</sub>O) by
the loss of guest H<sub>2</sub>O molecules. The desolvated PCPs <b>1</b> and <b>2</b> with the same formula [CuĀ(CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>(bpp)<sub>2</sub>] showed distinguishable
structures, suggesting PCP polymorphs. In addition, their adsorption
behaviors were completely different: <b>1</b> showed adsorption
with the structural transformation from closed to open forms, while <b>2</b> appeared to expand its framework for only as long as was
required for the passage of guest molecules. To the best of our knowledge,
PCP polymorphs showing either of two different types of flexible pores
are very rare
Porous Coordination Polymer Polymorphs with Different Flexible Pores Using a Structurally Flexible and Bent 1,3-Bis(4-pyridyl)propane Ligand
Porous
coordination polymer (PCP) polymorphs with the formula [CuĀ(CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>(bpp)<sub>2</sub>]<sub><i>n</i></sub> [<b>1</b> and <b>2</b>, where bpp =
1,3-bisĀ(4-pyridyl)Āpropane] have been synthesized and crystallographically
characterized, and their distinguishable porous properties have been
investigated. <b>1</b> was obtained by the removal of guest
acetone molecules from one-dimensional PCP {[CuĀ(CF<sub>3</sub>SO<sub>3</sub>)Ā(bpp)<sub>2</sub>]Ā·CF<sub>3</sub>SO<sub>3</sub>Ā·2acetone}<sub><i>n</i></sub> (<b>1</b>ā2acetone), while <b>2</b> was derived from two-dimensional PCP {[CuĀ(CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>(bpp)<sub>2</sub>]Ā·H<sub>2</sub>O}<sub><i>n</i></sub> (<b>2</b>āH<sub>2</sub>O) by
the loss of guest H<sub>2</sub>O molecules. The desolvated PCPs <b>1</b> and <b>2</b> with the same formula [CuĀ(CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>(bpp)<sub>2</sub>] showed distinguishable
structures, suggesting PCP polymorphs. In addition, their adsorption
behaviors were completely different: <b>1</b> showed adsorption
with the structural transformation from closed to open forms, while <b>2</b> appeared to expand its framework for only as long as was
required for the passage of guest molecules. To the best of our knowledge,
PCP polymorphs showing either of two different types of flexible pores
are very rare
Porous Coordination Polymer Polymorphs with Different Flexible Pores Using a Structurally Flexible and Bent 1,3-Bis(4-pyridyl)propane Ligand
Porous
coordination polymer (PCP) polymorphs with the formula [CuĀ(CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>(bpp)<sub>2</sub>]<sub><i>n</i></sub> [<b>1</b> and <b>2</b>, where bpp =
1,3-bisĀ(4-pyridyl)Āpropane] have been synthesized and crystallographically
characterized, and their distinguishable porous properties have been
investigated. <b>1</b> was obtained by the removal of guest
acetone molecules from one-dimensional PCP {[CuĀ(CF<sub>3</sub>SO<sub>3</sub>)Ā(bpp)<sub>2</sub>]Ā·CF<sub>3</sub>SO<sub>3</sub>Ā·2acetone}<sub><i>n</i></sub> (<b>1</b>ā2acetone), while <b>2</b> was derived from two-dimensional PCP {[CuĀ(CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>(bpp)<sub>2</sub>]Ā·H<sub>2</sub>O}<sub><i>n</i></sub> (<b>2</b>āH<sub>2</sub>O) by
the loss of guest H<sub>2</sub>O molecules. The desolvated PCPs <b>1</b> and <b>2</b> with the same formula [CuĀ(CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>(bpp)<sub>2</sub>] showed distinguishable
structures, suggesting PCP polymorphs. In addition, their adsorption
behaviors were completely different: <b>1</b> showed adsorption
with the structural transformation from closed to open forms, while <b>2</b> appeared to expand its framework for only as long as was
required for the passage of guest molecules. To the best of our knowledge,
PCP polymorphs showing either of two different types of flexible pores
are very rare
An Electrically Conductive Single-Component DonorāAcceptorāDonor Aggregate with Hydrogen-Bonding Lattice
An
electrically conductive DāAāD aggregate composed of
a single component was first constructed by use of a protonated bimetal
dithiolate (complex <b>1H</b><sub><b>2</b></sub>). The
crystal structure of complex <b>1H</b><sub><b>2</b></sub> has one-dimensional (1-D) Ļ-stacking columns where the D and
A moieties are placed in a segregated-stacking manner. In addition,
these segregated-stacking 1-D columns are stabilized by hydrogen bonds.
The result of a theoretical band calculation suggests that a conduction
pathway forms along these 1-D columns. The transport property of complex <b>1H</b><sub><b>2</b></sub> is semiconducting (<i>E</i><sub>a</sub> = 0.29 eV, Ļ<sub>rt</sub> = 9.1 Ć 10<sup>4</sup> Ī© cm) at ambient pressure; however, the resistivity
becomes much lower upon applying high pressure up to 8.8 GPa (<i>E</i><sub>a</sub> = 0.13 eV, Ļ<sub>rt</sub> = 6.2 Ć
10 Ī© cm at 8.8 GPa). The pressure dependence of structural and
optical changes indicates that the enhancement of conductivity is
attributed to not only an increase of ĻāĻ overlapping
but also a unique pressure-induced intramolecular charge transfer
from D to A moieties in this DāAāD aggregate
An Electrically Conductive Single-Component DonorāAcceptorāDonor Aggregate with Hydrogen-Bonding Lattice
An
electrically conductive DāAāD aggregate composed of
a single component was first constructed by use of a protonated bimetal
dithiolate (complex <b>1H</b><sub><b>2</b></sub>). The
crystal structure of complex <b>1H</b><sub><b>2</b></sub> has one-dimensional (1-D) Ļ-stacking columns where the D and
A moieties are placed in a segregated-stacking manner. In addition,
these segregated-stacking 1-D columns are stabilized by hydrogen bonds.
The result of a theoretical band calculation suggests that a conduction
pathway forms along these 1-D columns. The transport property of complex <b>1H</b><sub><b>2</b></sub> is semiconducting (<i>E</i><sub>a</sub> = 0.29 eV, Ļ<sub>rt</sub> = 9.1 Ć 10<sup>4</sup> Ī© cm) at ambient pressure; however, the resistivity
becomes much lower upon applying high pressure up to 8.8 GPa (<i>E</i><sub>a</sub> = 0.13 eV, Ļ<sub>rt</sub> = 6.2 Ć
10 Ī© cm at 8.8 GPa). The pressure dependence of structural and
optical changes indicates that the enhancement of conductivity is
attributed to not only an increase of ĻāĻ overlapping
but also a unique pressure-induced intramolecular charge transfer
from D to A moieties in this DāAāD aggregate