A benzoquinone-imidazole hybrid organic anolyte for aqueous redox flow batteries.

A benzoquinone derivative annelated by two imidazole rings was investigated as an organic anolyte of aqueous redox flow batteries. The anolyte showed a high solubility of 0.18 M in 1 M KOH aqueous solution and exhibited a one-step two-electron reversible redox wave with a half-wave potential of -0.59 V VS. SHE. An aqueous redox flow cell comprising the benzoquinone-imidazole hybrid as the anolyte and potassium ferrocyanide as the catholyte showed an operating voltage of ∼1.1 V and minimum capacity fading of over 220 cycles.

Voltammetric and In Situ Spectroscopic Investigations on the Redox Processes of Trioxotriangulene Neutral Radicals on Graphite Electrodes.

To investigate the microscopic electrochemical dynamics of a stable trioxotriangulene (TOT) organic neutral π-radical on a graphite electrode surface, voltammetric and in situ infrared (IR) spectroelectrochemical studies were conducted using electrolyte solutions containing TOT monoanions. Upright columnar crystals (face-on alignment) of the TOT neutral radical were preferentially formed and dissolved in a rather reversible manner in the electrolyte with a low concentration of TOT monoanion under electrochemical conditions; however, more flat-lying columnar crystals (edge-on alignment) were formed in a higher concentration electrolyte. The flat-lying crystals remained on the graphite surface even at a fully reduced potential, owing to the lack of direct π-π interactions between the molecules and the graphite electrode. In situ IR attenuated total reflectance spectroscopy analyses successfully characterized the alignment of the columnar crystals of the TOT neutral radicals and their electrochemical behaviors, including the possible origins of the irreversible redox reaction of TOT on the graphite electrode.

Real-time monitoring of enzyme-catalyzed phosphoribosylation of anti-influenza prodrug favipiravir by time-lapse nuclear magnetic resonance spectroscopy.

Favipiravir (brand name Avigan), a widely known anti-influenza prodrug, is metabolized by endogenous enzymes of host cells to generate the active form, which exerts inhibition of viral RNA-dependent RNA polymerase activity; first, favipiravir is converted to its phosphoribosylated form, favipiravir-ribofuranosyl-5'-monophosphate (favipiravir-RMP), by hypoxanthine-guanine phosphoribosyltransferase (HGPRT). Because this phosphoribosylation reaction is the rate-determining step in the generation of the active metabolite, quantitative and real-time monitoring of the HGPRT-catalyzed reaction is essential to understanding the pharmacokinetics of favipiravir. However, assay methods enabling such monitoring have not been established. 19 F- or 31 P-based nuclear magnetic resonance (NMR) are powerful techniques for observation of intermolecular interactions, chemical reactions, and metabolism of molecules of interest, given that NMR signals of the heteronuclei sensitively reflect changes in the chemical environment of these moieties. Here, we demonstrated direct, sensitive, target-selective, nondestructive, and real-time observation of HGPRT-catalyzed conversion of favipiravir to favipiravir-RMP by performing time-lapse 19 F-NMR monitoring of the fluorine atom of favipiravir. In addition, we showed that 31 P-NMR can be used for real-time observation of the identical reaction by monitoring phosphorus atoms of the phosphoribosyl group of favipiravir-RMP and of the pyrophosphate product of that reaction. Furthermore, we demonstrated that NMR approaches permit the determination of general parameters of enzymatic activity such as Vmax and Km . This method not only can be widely employed in enzyme assays, but also may be of use in the screening and development of new favipiravir-analog antiviral prodrugs that can be phosphoribosylated more efficiently by HGPRT, which would increase the intracellular concentration of the drug's active form. The techniques demonstrated in this study would allow more detailed investigation of the pharmacokinetics of fluorinated drugs, and might significantly contribute to opening new avenues for widespread pharmaceutical studies.

Double-σ-Bonded Close-Shell Dimers and Peroxy-Linked Open-Shell Dimer Derived from a C3 Symmetric Trioxophenalenyl Neutral Diradical.

A novel neutral diradical of π-extended phenalenyl derivative having three oxo-groups, tri-tert-butyl-1,4,7-trioxophenalenyl, and two types of the corresponding σ-dimers were investigated. Quantum chemical calculations showed that the neutral diradical is in triplet ground state having doubly degenerate singly occupied molecular orbitals. The neutral diradical undergoes a σ-dimerization, generating two types of σ-dimers immediately after the preparation. One of the σ-dimers, which was selectively generated in the crystalline state, was a close-shell dimer linked through double-σ-bonds on the phenalenyl skeleton with a long C-C bond length of 1.66 Å. The other σ-dimer, which existed only in the solution state, was a peroxy-linked open-shell dimer in which one σ-bond was formed between two oxygen atoms. Furthermore, the temperature-dependent 1 H NMR and ESR spectra revealed that these σ-dimers are in equilibrium in the solution state by the reversible σ-bond formation/cleavage via the neutral diradical as a key intermediate.

Design and Synthesis of a C3 Symmetrical Phenalenyl Derivative with Three Oxo Groups by Regioselective Deoxygenation/Oxygenation.

Tri-tert-butylated 4,7-dihydroxyphenalenone was designed and synthesized from a corresponding 4,9-dimethoxyphenalenone derivative by regioselective deoxygenation/oxygenation. The 4,7-dihydroxyphenalenone derivative showed a chromic behavior accompanied by protonation and deprotonation, giving monocation and dianion species, respectively, and their C3 symmetric electronic structures were elucidated by experimental and theoretical methods.

A Redox-Active Microporous Organosiloxane Containing a Stable Neutral Radical, Trioxotriangulene.

A new silyl-substituted trioxotriangulene (TOT) neutral radical and corresponding porous organosiloxanes (POSs) were synthesized. The neutral radical exhibited a peculiarly high stability and formed a diamagnetic π-dimer characteristic to TOT neutral radicals stabilized by the strong multiple SOMO-SOMO interaction in both solution and solid states. POSs including TOT units within the organosiloxane-wall were prepared by polycondensation of the silyl groups and formed microporous structures with ∼1 nm-size diameters. Redox ability of TOT units in the POS was demonstrated by the treatment of oxidant/reductant in heterogeneous suspension condition, where the TOT units were reversibly converted between reduced and neutral radical species. Furthermore, the solid-state electrochemical measurements of the POS revealed the reversible multi-stage redox ability of TOT units involving polyanionic species within the organosiloxane-wall.

Synthesis and Physical Properties of Trioxotriangulene Having Methoxy and Hydroxy Groups at α-Positions: Electronic and Steric Effects of Substituent Groups and Intramolecular Hydrogen Bonds.

New 4,8,12-trioxotriangulene (TOT) neutral radical derivatives having three methoxy and hydroxy groups at the α-positions were synthesized, and the substituent effects on the electronic spin and redox properties were elucidated in the theoretical and experimental methods. Due to the small SOMO coefficients at the α-positions of TOT, the methoxy groups in the TOT neutral radical had negligible effects on the electronic spin structure and redox ability. On the other hand, methoxy groups greatly increased the LUMO energy having large coefficients at α-positions and, thus, caused a remarkable negative-potential shift of the redox wave of anion species involving the dianion and trianion species. Converting the methoxy groups to hydroxy groups caused a dramatic change in the electronic structure of TOT, where the intramolecular hydrogen bonds between hydroxy groups and oxo groups strongly attracted a minus charge on the TOT skeleton. The HOMO energy of the monoanion species was significantly reduced, causing a blue shift of the HOMO-LUMO transition and an anodic shift of the redox potential. In addition, due to the steric repulsion smaller than that of the methoxy group, the hydroxy derivative showed a more planar molecular structure and a strong π-stacking ability.

High Capacity and Energy Density Organic Lithium-Ion Battery Based on Buckypaper with Stable π-Radical.

Owing to an increasing demand on high performance and rare-metal free energy storage systems, organic rechargeable battery has attracted much attention. To increase the capacity of the whole battery, we have fabricated coin-type buckypaper cells composed of a trioxotriangulene neutral radical derivative (H3 TOT) and single-walled carbon nanotubes as a cathode and lithium metal plate as an anode without current collector. The cells exhibited a stable charge-discharge behavior even at a 90 wt % H3 TOT content with a high-rate performance of 10 C originating from high electrical conductivity of H3 TOT. Furthermore, based on the four-stage redox ability of H3 TOT, the H3 TOT 90 wt % cathode showed a high capacity of approximately 260 mAh g-1 and a high energy density of 546 Wh g-1 . In view of the simple fabrication of the cathode and excellent performance, TOT-based buckypaper will open a new strategy for the flexible cells for next-generation energy storages.

2D Coordination Network of Trioxotriangulene with Multiple Redox Abilities and Its Rechargeable Battery Performance.

A three-fold symmetric trioxotriangulene derivative with three pyridyl groups as coordinating sites was designed and synthesized. In a cyclic voltammetry measurement, the trioxotriangulene skeleton exhibited a multi-stage redox ability from neutral radical to radical tetra-anion species. In the zinc complex of monoanion species, three pyridyl groups coordinated to the zinc ion to build up a two-dimensional coordination network with a cavity larger than 12 Å in diameter. This complex was utilized as a cathode active material of a lithium ion battery, and it exhibited a capacity of ca. 60 mAh g-1 per the weight of the active material with a stable cycling performance up to 1000 cycles. This work shows that the coordination network formed by the trioxotriangulene-based ligand was effective in the improvement of cycle performance of the organic rechargeable battery.

High-field NMR with dissolution triplet-DNP.

Dissolution dynamic nuclear polarization (DNP) has wide variety of important applications such as real-time monitoring of chemical reactions and metabolic imaging. We construct DNP using photoexcited triplet electron spins (Triplet-DNP) apparatus combined with dissolution apparatus for solution NMR in a high magnetic field. Triplet-DNP enables us to obtain high nuclear polarization at room temperature. Solid-state samples polarized by Triplet-DNP are transferred to a superconducting magnet and dissolved by injecting aqueous solvents. The 13C polarization of 0.22% has been obtained for [caryboxy-13C]benzoic acid-d in the liquid state. Our results show that Triplet-DNP can be applied to real-time monitoring with solution NMR.

Air-Stable Thin Films with High and Anisotropic Electrical Conductivities Composed of a Carbon-Centered Neutral π-Radical.

Air-stable thin films (50-720 nm thickness) composed of a carbon-centered neutral π-radical with high and anisotropic electrical conductivities were fabricated by vapor deposition of 4,8,12-trioxotriangulene (TOT). The thin films were air-stable over 15 months and were the aggregate of TOT microcrystals, in which a one-dimensional π-stacking column was formed through the strong singly occupied molecular orbital (SOMO)-SOMO interaction with two-electron-multicenter bond among the spin-delocalized π-planes. The orientations of the one-dimensional column of TOT were changed depending on the deposition rate and substrates, where face-on-oriented thin films were epitaxially grown on the graphite 0001 surface, and edge-on-oriented thin films were grown on glass, SiO2, and indium tin oxide substrates under a high-deposition rate condition. The films showed high electrical conductivities of 2.5 × 10-2 and 5.9 × 10-5 S cm-1 along and perpendicular to the π-stacking column, respectively, for an edge-on oriented thin film.

Colored Ionic Liquid Based on Stable Polycyclic Anion Salt Showing Halochromism with HCl Vapor.

A sodium salt of a polycyclic trioxotriangulene (TOT) anion with six triethylene glycol chains exhibiting the formation of a colored ionic liquid at room temperature was synthesized. The ionic liquid is air- and water-stable, reflecting thermodynamic stabilization of a charge-delocalized TOT anion. Upon protonation of the TOT anion, the salt shows halochromic behaviors in solution and even in the neat liquid state with HCl vapor. The ionic liquid shows no morphological change with the chromism, presumably as a result of poor intermolecular interactions between π skeletons.

Patent Application Trends of Induced Pluripotent Stem Cell Technologies in the United States, Japanese, and European Applications.

Patent application trends were investigated for induced pluripotent stem cell (iPSC) technologies, particularly disease-specific cell technologies related to iPSCs, in the U.S., Japanese, and European applications during 2017. The number of patent applications for iPSC technologies was 1516 in the United States, 895 in Japan, and 420 in Europe, with 5% of applications for disease-specific cell technologies. In contrast, the percentages of patent applications for iPSC preparation and differentiation technologies were 17% and 23%, respectively. Patent applications for disease-specific cell technologies were classified into four technical fields and 14 disorder groups. In the technical fields, patent applications for genetically engineered cell technologies were prominent, accounting for 63%, 50%, and 65% of the U.S., Japanese, and European applications for 11, 8, and 7 disorder groups, respectively. In the disorder groups, the percentages of patent applications for neurological disorders were 40%, 32%, and 40% of the U.S., Japanese, and European applications, respectively, which were filed in four technical fields in the U.S. and Japanese applications. The U.S. patent applications for disease-specific cell technologies were filed by applicants in the United States, Japan, France, Belgium, Italy, Korea, and Canada; however, patent applications filed by those in Belgium, Italy, and Canada were not found in the Japanese and European applications. The percentages of patent applications filed by the U.S. applicants were 72%, 55%, and 65% of the U.S., Japanese, and European applications, respectively. Most patent applications filed by the U.S. applicants were in the field of genetically engineered cells for 11 disorder groups, which mostly included neurological and blood disorders. Japanese applicants mainly filed patent applications for drug screening technologies; subjects included five disorder groups, particularly neurological and bone/articular disorders. French applicants filed patent applications for neurological disorders in the field of genetically engineered cells and drug screening technologies. Korean applicants filed patent applications for patient-derived cell technologies for neurological, metabolic, and chromosomal/genetic disorders. In conclusion, more than half of patent applications were for genetically engineered cells for 11 disorders, most of which were filed by U.S. applicants.

Intramolecular Magnetic Interaction of Spin-Delocalized Neutral Radicals through m-Phenylene Spacers.

A new diradical having two 4,8,10-trioxotriangulene (TOT) neutral radical units linked through an m-phenylene moiety was synthesized and characterized by ESR measurements. An electrochemical study showed that the diradical undergoes two one-electron reductions to generate corresponding dianion species, suggesting the electronic interaction between two TOT units through the π-conjugated spacer. A strong intramolecular interaction between the two TOT units gives rise to the spin-projected small hyperfine couplings in comparison with those of the monomer. Furthermore, the temperature dependent ESR measurement revealed that the dimer behaves as an S=1 species in the ground state with a ferromagnetic interaction of 2 J/kB =+7±3 K.

Microscopic Behavior of Active Materials Inside a TCNQ-Based Lithium-Ion Rechargeable Battery by in Situ 2D ESR Measurements.

Real-time spectroscopic measurements in rechargeable batteries are important to understand the electrochemistry of the batteries at the molecular level and improve relevant functionalities. We have applied in situ two-dimensional (2D) electron spin resonance (ESR) spectroscopy to a well-known organic lithium-ion battery, which is composed of 7,7,8,8-tetracyanoquinodimethane (TCNQ) as the cathode-active material and a lithium metal anode electrode. The TCNQ rechargeable battery is suitable for investigating electrochemistry in the battery in terms of behavior of electron spin at microscopic levels on both the cathode and anode electrodes. We have discussed two-stage oxidation/reduction reactions of TCNQ, Li deposited/stripped process and their resulting dendritic and/or mossy microstructures, clearly elucidating the cause of the cell capacity degradation upon the charge-discharge cycles. The observed in situ ESR spectra showed that the degradation of the cell capacity was due to the elution of the active molecules, which caused the increase of ion conductivity by the substitution of the electrolyte solution for the adsorbed active materials on the conductive carbon surface. To discriminate paramagnetic species during the charge-discharge process, the generalized 2D correlation spectroscopy has been applied to characterize time-dependent in situ ESR spectra. The correlation analysis with in situ ESR helps us identify the paramagnetic species occurring in the battery cell in a straightforward manner.

Dynamic Nuclear Polarization using Photoexcited Triplet Electron Spins in Eutectic Mixtures.

Dynamic nuclear polarization using photoexcited triplet electrons (Triplet-DNP) is a method to significantly enhance nuclear spin polarization even in a low magnetic field and at room temperature. Pentacene has been practically used as an efficient polarizing agent for Triplet-DNP. In this study, we demonstrate room temperature 1H and 13C hyperpolarization of eutectic mixtures of deuterated benzoic acid doped with pentacene and a target molecule such as salicylic acid, nicotinic acid, or 2-naphthoic acid. These molecules are otherwise difficult to hyperpolarize by Triplet-DNP due to the low pentacene dopabilities of these molecules. The highest 1H polarization of 1.2% has been obtained for the eutectic mixture of salicylic acid in 0.39 T. The present sample preparation is a crucial method to widen the range of applications of Triplet-DNP to chemical and biomedical analyses.

Selective Formation of Conductive Network by Radical-Induced Oxidation.

Cd-based coordination networks having channels were formed selectively by using a redox-active aromatic ligand 2,5,8-tri(4-pyridyl)1,3-diazaphenalene (TPDAP, H(+)1(-)). An electron-conductive network having a π-π stacking columnar structure of TPDAP formed in the presence of a trace amount of TPDAP radical (1(•)). In contrast, a nonconductive network having a dimer unit of H(+)1(-) formed in the absence of 1(•). These results suggest the presence of a unique oxidation mechanism of TPDAP induced by formation of H(+)1(-)-1(•) dimer, which was initiated by a trace amount of 1(•). The dimerization increased HOMO level of H(+)1(-) moiety within the dimer to generate further radicals that could not form when H(+)1(-) was well isolated in CH3OH.

Endoscopic submucosal dissection for early gastric cancer without interruption of warfarin and aspirin.

Many guidelines for the management of antithrombotic therapy in endoscopic procedures state that warfarin should be replaced by heparin in high risk endoscopic procedures. However, heparin bridging therapy is costly, requires a long hospital stay, and is indicated as a risk factor for bleeding after endoscopic submucosal dissection (ESD). It is not yet clear whether it is better to perform gastric ESD on continuous warfarin therapy or heparin bridging therapy. We report the case of a 65-year-old Japanese man who had been diagnosed with early gastric cancer. He had a past medical history of metallic valve replacement for mitral valve regurgitation, coronary artery disease with bare metal stent, and coronary artery bypass graft. Warfarin and low dose aspirin had been used to prevent thromboembolic events in the metallic mitral valve and coronary artery stent. We performed gastric ESD safely on continuous warfarin and low dose aspirin without any complications.

Continuous aspirin use does not increase post-endoscopic dissection bleeding risk for gastric neoplasms in patients on antiplatelet therapy.

BACKGROUND AND STUDY AIMS: Discontinuation of all antiplatelet agents before endoscopic procedures may cause serious complications in some patients. The aim of this study was to evaluate the hemorrhagic risk of post-endoscopic submucosal dissection (ESD) in patients on antiplatelet therapy (APT). PATIENTS AND METHODS: The subjects were 350 patients (377 lesions) who underwent gastric ESD between January 2007 and July 2013. The patients were categorized based on antiplatelet therapies. The primary outcome was post-ESD bleeding. Multivariate analysis was performed to identify independent risk factors for post-ESD bleeding. RESULTS: The patients were categorized into three groups: (1) no APT, 261 patients with 281 lesions; (2) single APT, 58 patients with 63 lesions (53 patients with low dose aspirin [LDA] and 5 patients with a thienopyridine); and (3) dual APT (DAPT), 31 patients with 33 lesions (DAPT with LDA and a thienopyridine). Post-ESD bleeding occurred in 16 of 261 patients in the no APT group (6.1 %), 9 of 58 patients in the single APT group (15.5 %), and 11 of 31 patients in the DAPT group (35.5 %). In multivariate analysis with a Cox proportional hazards model in the no APT and single APT groups, APT (HR 2.7, 95 %CI 1.1 - 6.6, P = 0.03) and diameter of the resected specimen of 40 mm or greater (HR 2.7, 95 %CI 1.2 - 5.9, P = 0.01) were significant risk factors for post-ESD bleeding. In multivariate analysis in the no APT and DAPT groups, DAPT was the only significant risk factor for post-ESD bleeding (HR 16.3, 95 %CI 3.4 - 78.2, P < 0.01). Continuous LDA was not a significant risk factor for post-ESD bleeding in both analyses (HR 0.8, 95 %CI 0.2 - 3.6, P = 0.72 in the no APT and single APT groups; HR 1.0, 95 %CI 0.2 - 5.1, P = 0.95 in the no APT and DAPT groups). CONCLUSIONS: APT increased the risk for post-ESD bleeding, and DAPT markedly increased the risk for bleeding. Continuous LDA did not produce an additional hemorrhagic risk in all patients treated with APT. Thus, patients treated with APT should be careful monitored for post-ESD bleeding, and LDA should not be interrupted in patients with a high thromboembolic risk.

Formation of a nanometer-thick water layer at high humidity on a dynamic crystalline material composed of multi-interactive molecules.

Crystalline powders self-assembled from interactive discrete molecules reversibly transformed from a porous structure to a 2D one with a nanometer-thick H2O layer by hydration/dehydration. Multi-point weak intermolecular interactions contributed to maintenance of each phase. This structure transformation induced a humidity-dependent ion conductivity change from insulator to 3.4 × 10(-3) S cm(-1).