34 research outputs found
Noticias
The <i>K</i><sub>4</sub> structure was theoretically predicted for trivalent chemical species,
such as sp<sup>2</sup> carbon. However, since attempts to synthesize
the <i>K</i><sub>4</sub> carbon have not succeeded, this
allotrope has been regarded as a crystal form that might not exist
in nature. In the present work, we carried out electrochemical crystallization
of the radical anion salts of a triangular molecule, naphthalene diimide
(NDI)-Î, using various electrolytes. X-ray crystal analysis
of the obtained crystals revealed the <i>K</i><sub>4</sub> structure, which was formed by the unique intermolecular Ï
overlap directed toward three directions from the triangular-shape
NDI-Î radical anions. Electron paramagnetic resonance and static
magnetic measurements confirmed the radical anion state of NDI-Î
and indicated an antiferromagnetic intermolecular interaction with
the Weiss constant of Ξ = â10 K. The band structure calculation
suggested characteristic features of the present material, such as
a metallic ground state, Dirac cones, and flat bands
Monovalent and Mixed-Valent Potassium Salts of [1,2,5]Thiadiazolo[3,4-<i>f</i>][1,10]phenanthroline 1,1-Dioxide: A Radical Anion for Multidimensional Network Structures
A novel phenanthlorine derivative, [1,2,5]ÂthiadiazoloÂ[3,4-<i>f</i>]Â[1,10]Âphenanthroline 1,1-dioxide (tdapO<sub>2</sub>),
was prepared to act as a radical-anion building block for coordination
polymers. The crystal structures and magnetic properties of the monovalent
and mixed-valent radical-anion salts K·tdapO<sub>2</sub> and
K·(tdapO<sub>2</sub>)<sub>2</sub> were elucidated and confirm
the possibility of tdapO<sub>2</sub> to act as a bridging ligand and
its capability to exhibit magnetic ordering at 15 K
Discovery of a âBipolar Chargingâ Mechanism in the Solid-State Electrochemical Process of a Flexible MetalâOrganic Framework
Metalâorganic
frameworks (MOFs) are well-known for their application to various
types of energy storage; nevertheless, their potential in electron
storage has scarcely been investigated. Indeed, the synthetic strategy
of MOFs toward the pseudocapactive materials is still absent due to
the lack of a detailed insight into the solid-state redox process
of MOFs. In this manuscript, we reported the discovery of a new electrochemical
mechanism, namely, âbipolar chargingâ mechanism by analyzing
the solid-state electrochemical process of a flexible redox active
MOF. In a single redox cycle, not only the Li-ions but also the bulky
anions are separately intercalated into the pores of the MOF and contribute
to the total capacity. With this âbipolar chargingâ
mechanism, a general synthetic strategy could be proposed. Furthermore,
MOF materials employing this mechanism may exhibit remarkable reactivity
and high cyclic stability and be adopted as versatile electrode materials
in various battery architectures
Monovalent and Mixed-Valent Potassium Salts of [1,2,5]Thiadiazolo[3,4-<i>f</i>][1,10]phenanthroline 1,1-Dioxide: A Radical Anion for Multidimensional Network Structures
A novel phenanthlorine derivative, [1,2,5]ÂthiadiazoloÂ[3,4-<i>f</i>]Â[1,10]Âphenanthroline 1,1-dioxide (tdapO<sub>2</sub>),
was prepared to act as a radical-anion building block for coordination
polymers. The crystal structures and magnetic properties of the monovalent
and mixed-valent radical-anion salts K·tdapO<sub>2</sub> and
K·(tdapO<sub>2</sub>)<sub>2</sub> were elucidated and confirm
the possibility of tdapO<sub>2</sub> to act as a bridging ligand and
its capability to exhibit magnetic ordering at 15 K
Monitoring the Solid-State Electrochemistry of Cu(2,7-AQDC) (AQDC = Anthraquinone Dicarboxylate) in a Lithium Battery: Coexistence of Metal and Ligand Redox Activities in a MetalâOrganic Framework
By
adopting a facile synthetic strategy, we obtained a microporous
redox-active metalâorganic framework (MOF), namely, CuÂ(2,7-AQDC)
(2,7-H<sub>2</sub>AQDC = 2,7-anthraquinonedicarboxylic acid) (<b>1</b>), and utilized it as a cathode active material in lithium
batteries. With a voltage window of 4.0â1.7 V, both metal clusters
and anthraquinone groups in the ligands exhibited reversible redox
activity. The valence change of copper cations was clearly evidenced
by <i>in situ</i> XANES analysis. By controlling the voltage
window of operation, extremely high recyclability of batteries was
achieved, suggesting the framework was robust. This MOF is the first
example of a porous material showing independent redox activity on
both metal cluster nodes and ligand sites
Monitoring the Solid-State Electrochemistry of Cu(2,7-AQDC) (AQDC = Anthraquinone Dicarboxylate) in a Lithium Battery: Coexistence of Metal and Ligand Redox Activities in a MetalâOrganic Framework
By
adopting a facile synthetic strategy, we obtained a microporous
redox-active metalâorganic framework (MOF), namely, CuÂ(2,7-AQDC)
(2,7-H<sub>2</sub>AQDC = 2,7-anthraquinonedicarboxylic acid) (<b>1</b>), and utilized it as a cathode active material in lithium
batteries. With a voltage window of 4.0â1.7 V, both metal clusters
and anthraquinone groups in the ligands exhibited reversible redox
activity. The valence change of copper cations was clearly evidenced
by <i>in situ</i> XANES analysis. By controlling the voltage
window of operation, extremely high recyclability of batteries was
achieved, suggesting the framework was robust. This MOF is the first
example of a porous material showing independent redox activity on
both metal cluster nodes and ligand sites
Discovery of a âBipolar Chargingâ Mechanism in the Solid-State Electrochemical Process of a Flexible MetalâOrganic Framework
Metalâorganic
frameworks (MOFs) are well-known for their application to various
types of energy storage; nevertheless, their potential in electron
storage has scarcely been investigated. Indeed, the synthetic strategy
of MOFs toward the pseudocapactive materials is still absent due to
the lack of a detailed insight into the solid-state redox process
of MOFs. In this manuscript, we reported the discovery of a new electrochemical
mechanism, namely, âbipolar chargingâ mechanism by analyzing
the solid-state electrochemical process of a flexible redox active
MOF. In a single redox cycle, not only the Li-ions but also the bulky
anions are separately intercalated into the pores of the MOF and contribute
to the total capacity. With this âbipolar chargingâ
mechanism, a general synthetic strategy could be proposed. Furthermore,
MOF materials employing this mechanism may exhibit remarkable reactivity
and high cyclic stability and be adopted as versatile electrode materials
in various battery architectures
Ambipolar Carrier Injections Governed by Electrochemical Potentials of Ionic Liquids in Electric-Double-Layer Thin-Film Transistors of Lead- and Titanyl-Phthalocyanine
Electric-double-layer
thin-film transistors of lead- and titanyl-phthalocyanine
with ionic-liquid gate dielectrics exhibit ambipolar behavior with
low threshold voltages less than ±2 V. Their threshold gate voltages
are found to depend significantly on the ionic liquids, being proportional
to the electrochemical potential of the ionic liquids. This dependence
can be understood by an energy diagram of the frontier orbitals of
PbPc and TiOPc, and the electrochemical potentials of the ionic liquids
Ionic-Liquid Component Dependence of Carrier Injection and Mobility for Electric-Double-Layer Organic Thin-Film Transistors
Electrostatic carrier injection and electrochemical doping
of octathio[8]Âcirculene
thin films is examined for six kinds of ionic liquids using in situ
cyclic voltammetry (CV) and conductivity measurements. The frequency
dependence of the capacitance measurements indicates that the ionic
liquids form electric-double-layers (EDLs) below 10<sup>2</sup> Hz.
The performance of the EDL-organic thin film transistors (OTFTs) of
octathio[8]Âcirculene demonstrates that the transistor carrier mobility
shows a linear decrease with an increase in the capacitance of the
ionic liquids. In contrast, the electrochemical oxidation potentials
and the threshold voltage of the EDL-OTFT are governed only by one
component of the ionic liquid; namely, the electrostatic and electrochemical
hole injections are significantly affected by the anions
Ambipolar Transport in Phase-Separated Thin Films of p- and nâType Vanadylporphyrazines with Two-Dimensional Percolation
Phase separation in thin films of
organic p- and n-type semiconductors
has attracted much attention for applications as bulk heterojunctions
in organic photovoltaic devices and thin-film transistors (OTFTs).
In the present study, we examined the structures, electronic states,
and transistor performance of the codeposited thin films of p- and
n-type porphyrazines, vanadylphthalocyanine (VOPc), and vanadyltetrakisÂ(1,2,5-thiadiazole)Âporphyrazine
with various mixing ratios. The transistors exhibited ambipolar performance,
in which the p-type mobility increases with an increase in the VOPc
ratio, and vice versa for the n-type mobility. This can be explained
by a phase separation in these thin films. In addition, the mixing
ratio dependence of the transistor parameters such as mobility and
on/off ratio clearly indicated that the hole and electron carrier
transports in the thin films are governed by the two-dimensional percolations
of the p- and n-type semiconductor domains, respectively. We also
fabricated electric-double-layer transistors of the codeposited thin
films with ionic liquid gate dielectrics and found significant improvements
in the mobility and threshold voltage and a high on/off ratio. The
complementary inverters composed by these OTFTs worked in the first
and third quadrants with a large signal gain over 10