Noticias

The <i>K</i>₄ structure was theoretically predicted for trivalent chemical species, such as sp² carbon. However, since attempts to synthesize the <i>K</i>₄ 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)-Δ, using various electrolytes. X-ray crystal analysis of the obtained crystals revealed the <i>K</i>₄ structure, which was formed by the unique intermolecular π overlap directed toward three directions from the triangular-shape NDI-Δ radical anions. Electron paramagnetic resonance and static magnetic measurements confirmed the radical anion state of NDI-Δ and indicated an antiferromagnetic intermolecular interaction with the Weiss constant of θ = −10 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]­thiadiazolo­[3,4-<i>f</i>]­[1,10]­phenanthroline 1,1-dioxide (tdapO₂), 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·tdapO₂ and K·(tdapO₂)₂ were elucidated and confirm the possibility of tdapO₂ to act as a bridging ligand and its capability to exhibit magnetic ordering at 15 K

Discovery of a “Bipolar Charging” Mechanism in the Solid-State Electrochemical Process of a Flexible Metal–Organic Framework

Metal–organic 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, “bipolar charging” 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 “bipolar charging” 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]­thiadiazolo­[3,4-<i>f</i>]­[1,10]­phenanthroline 1,1-dioxide (tdapO₂), 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·tdapO₂ and K·(tdapO₂)₂ were elucidated and confirm the possibility of tdapO₂ 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 Metal–Organic Framework

By adopting a facile synthetic strategy, we obtained a microporous redox-active metal–organic framework (MOF), namely, Cu­(2,7-AQDC) (2,7-H₂AQDC = 2,7-anthraquinonedicarboxylic acid) (<b>1</b>), and utilized it as a cathode active material in lithium batteries. With a voltage window of 4.0–1.7 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 Metal–Organic Framework

By adopting a facile synthetic strategy, we obtained a microporous redox-active metal–organic framework (MOF), namely, Cu­(2,7-AQDC) (2,7-H₂AQDC = 2,7-anthraquinonedicarboxylic acid) (<b>1</b>), and utilized it as a cathode active material in lithium batteries. With a voltage window of 4.0–1.7 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 “Bipolar Charging” Mechanism in the Solid-State Electrochemical Process of a Flexible Metal–Organic Framework

Metal–organic 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, “bipolar charging” 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 “bipolar charging” 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]­circulene 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 10² Hz. The performance of the EDL-organic thin film transistors (OTFTs) of octathio[8]­circulene 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 n‑Type 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 vanadyltetrakis­(1,2,5-thiadiazole)­porphyrazine 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