Solvent-Free Reaction for Unsymmetrical Organodisulfides with High Purity and Application as Cathode-Active Materials.

Unsymmetrical disulfides, in which different organic groups are bonded to disulfide bonds, have been synthesized by cross-coupling reactions using thiols as substrates. However, due to the low-binding energy of unsymmetrical disulfides, its disproportionation occurs based on the side reactions with nucleophilic thiols, resulting in the impurity of symmetric disulfides. In this study, we developed a solvent-free synthesis method for unsymmetrical disulfides using thiosulfonates, thiols, and a base. This synthetic method enabled us to obtain highly pure diaryl-substituted unsymmetrical disulfides with particularly low-binding energy without control over the nucleophilicity and elimination properties of the substrate. Furthermore, it was observed that the disproportionation of unsymmetrical disulfides occurred in the solvent. This means that solvent-free condition is one of the factors to obtain unsymmetrical disulfides. As a new application of unsymmetrical disulfides, we applied unsymmetrical disulfides to cathode active materials of lithium batteries based on the reversible multi-electron redox activity of S-S bonds. The batteries using unsymmetrical disulfide cathode-active materials with a carbon nanotube exhibited initial capacities of 127 and 158 Ah/kg, equal to 42 and 53% of their theoretical ones. We demonstrated that unsymmetrical disulfides could be used as cathode-active materials for rechargeable batteries.

Stability Modification of Dye-sensitized Solar Cells by Ruthenium Dyes Embedded on Eggshell Membranes.

Dye-sensitized solar cells (DSSCs) have been one of the most promising technologies to convert sunlight into electricity repeatedly based on the mechanism that dyes inject/accept electron into the metal oxides/from redox mediator. Specifically, N719 ([RuL2(NCS)2], L: 4,4'-dicarboxy-2,2'-bipyridine), immobilized on TiO2 through the interaction between its ligands (-COO- and -NCS) and the oxygen on the TiO2 surface, has been used as a conventional DSSC dye with high voltage. Nevertheless, -NCS ligands have been removed from Ru2+ in N719 due to UV irradiation and exchanged with H2O or OH- in electrolyte, resulting in voltage drop. In this work, we developed the first DSSC using the N719-adsorbed Eggshell (ESM)-TiO2 composite to maintain the immobilization of N719 on TiO2 through electrostatic interaction between the protein of ESM and N719. The DSSC using the composite maintained the voltage even after 12 h light irradiation, although the voltage of DSSC without ESM dropped drastically. It means that the ESM contributed to stable photovoltaic performances of DSSCs through the protection of NCS ligands of N719.

Assessment of Dye-Absorbed Eggshell Membrane Composites as Solid Polymer Electrolyte of Fuel Cells.

Recently, polymer electrolytes have been developed for high-performance and eco-friendly fuel cells. Among the candidates, eggshell membrane (ESM) has been promising because of its abundance to assemble various energy devices with low cost and its absorption ability of organic materials. In this work, we investigated fuel cells that included ESM-absorbing xanthene-, triphenylmethane-, and azo-type tar dye, which contained abundant hydrophilic groups, as polymer electrolytes. We found out two points: (1) that the fuel cells that included ESM-absorbing xanthene-type dye generated the highest I-V performance, and (2) the basic molecular structures of the tar dyes determined the correlation of the maximum power and proton conductivities.

Ultra-High-Capacity Lithium Metal Batteries Based on Multi-Electron Redox Reaction of Organopolysulfides including Conductive Organic Moieties.

Recently, organic polysulfides have been synthesized as cathode active materials exceeding the battery performance of sulfur. However, the conventional organic polysulfides have exhibited capacities lower than the theoretical capacity of sulfur because the π-organic moieties do not conjugate with the sulfur chains. In this work, the organopolysulfides, synthesized via inverse vulcanization using disulfide compounds, exhibited higher capacities equal to the theoretical capacity of sulfur because of enhanced electronic conductivity based on the conjugation between organic moieties and sulfur chains. Furthermore, the organopolysulfide including 1,3-dhitiol-2-thione moiety exhibited the highest capacity because of the enhanced electronic conductivity. This finding will pave the way to develop next-generation rechargeable batteries.

Azo Compounds as Active Materials of Energy Storage Systems.

The rapid evolution of electrical devices and the increasing demand for the supply of sustainable energy necessitate the development of high-performance energy storage systems such as rechargeable and redox flow batteries. However, these batteries typically contain inorganic active materials, which exhibit several critical drawbacks hindering further development. In this regard, azo compounds are promising alternatives, offering the benefits of fast kinetics, multi-electron redox reactions, and tunable (via structural adjustment) battery performance. Herein, we review the use of azo compounds as the active materials of rechargeable and redox flow batteries, discuss certain aspects of material design and electrochemical reaction mechanisms, and summarize the corresponding perspectives and research directions to facilitate further progress in this field.

Assessment of Eggshell Membrane as a New Type of Proton-Conductive Membrane in Fuel Cells.

Polymer electrolyte membrane fuel cells have recently attracted considerable attention as sustainable and eco-friendly electricity generation devices from the viewpoint of carbon neutrality. This study focuses on new discoveries related to the application of eggshell membranes to polymer electrolytes in the development of cheaper, more eco-friendly fuel cells. We observed the electricity generation of the fuel cells using an eggshell membrane as a proton-conductive material and a general carbonic acid aqueous solution. This new fuel cell will contribute to the continued improvement of available fuel cells at lower costs.

Water-Processable, Air-Stable Organic Nanoparticle-Carbon Nanotube Nanocomposites Exhibiting n-Type Thermoelectric Properties.

Water-dispersed organic base nanoparticles are utilized for the highly stable n-type doping of single-walled carbon nanotubes in aqueous dispersion. Long-term stability is often a critical challenge in the application of n-type organic conductors. The present n-type organic materials exhibit almost no degradation in the thermoelectric properties over months, in air.

Photoswitching of conductance of diarylethene-Au nanoparticle network.

A network composed of gold nanoparticles covered with diarylethene dithiophenols was prepared on an interdigitated nanogapped gold electrode to show the reversible photoswitching of the conductance due to the photochromism of the diarylethene molecules induced by UV and visible light.

New photoswitching unit for magnetic interaction: diarylethene with 2,5-bis(arylethynyl)-3-thienyl group.

Photoswitching of the intramolecular magnetic interaction was demonstrated using diarylethenes with 2,5-bis(arylethynyl)-4-methyl-3-thienyl side group. Two nitroxide radicals were placed at each end of the 2,5-bis(arylethynyl)-4-methyl-3-thienyl group. Three kinds of aryl groups, 2,5-thienylene, p-phenylene, and m-phenylene groups, were used in the arylethynyl moiety. The diarylethene photoswitching units have an extended pi-conjugated chain on one side of the diarylethene. The photochromic reactivity was dependent on the arylethynyl group. Diarylethenes with m-phenylene group showed an efficient photochromic reactivity. Along with the photochromic reaction the diarylethenes showed photoswitching of an ESR spectrum originating from the change in the magnetic interaction between two unpaired electrons. The open-ring isomer showed stronger exchange interaction than the photogenerated closed-ring isomer. The magnetic interaction between two radicals via the pi-conjugated chain was altered by photocyclization due to the change of the hybrid orbital at the 2-position of the thiophene ring from sp(2) to sp(3).

Effect of imino nitroxyl and nitronyl nitroxyl groups on the photochromic reactivity of diarylethenes.

Diarylethene derivatives having imino nitroxide and nitronyl nitroxide have been prepared to examine the effect of the radical substituents on the photochromic reactivity of 1,2-bis(2-methyl-1-benzothiophen-3-yl)perfluorocyclopentene. These radical substituents reduce the quantum yields of both cyclization and cycloreversion reactions. The nitronyl nitroxyl moiety is more effective to suppress the reactivity in comparison with the imino nitroxide moiety. [reaction: see text]

Electrochemical cyclization/cycloreversion reactions of diarylethenes.

[reaction: see text]. Electrochemical oxidation of diarylethene derivatives induced cyclization or cycloreversion reactions. The reaction mechanism was studied with CV, absorption spectra, and theoretical calculation.

Full-color photochromism of a fused dithienylethene trimer.

A diarylethene fused trimer, 1-(5-(2-(3,5-dimethyl-2-thienyl)hexafluorocyclopententen-1-yl)-2,4-dimethyl-3-thienyl)-2-(5-(2-(2,4-dimethyl-5-phenyl-3-thienyl)hexafluorocyclopentene-1-yl)-2,4-dimethyl-3-thienyl)hexafluorocyclopentene, was synthesized. The diarylethene derivative showed full-color photochromic performance by choosing appropriate wavelength of light.

Rotational isomerism involving an acetylenic carbon IV: synthesis and structure of bis(1,1';3',1"-terphenyl-2'-yl)ethynes: molecular design of sterically congested alkynes toward restricted rotation about acetylenic axis.

The title diphenylethyne derivative with 4-methylphenyl (tolyl) groups at all the ortho positions was synthesized by the Stille or Sonogashira coupling from the corresponding iodide. The X-ray structure revealed that the two terminal phenyl groups at the sp carbons are twisted by 63 degrees out of the coplanar conformation to avoid steric interactions between the tolyl groups. The relative stabilities of possible conformers were analyzed by the PM3 calculations. The axially chiral derivative with two methoxymethyl groups showed no evidence of restricted rotation about the acetylenic axis by VT NMR measurements, its barrier being less than 35 kJ mol(-1). The spectroscopic features and reactivities of this sterically congested alkyne are also described.