Electrooxidative copolymerization of 3,4-ethylenedioxithiophene (EDOT) and benzene from a mixture of the monomers with concentrations of 5 mM EDOT and 5 M benzene produced copolymer films on an anode surface. The formation of copolymer films and characterization of their electrochemical properties was confirmed using Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible absorption (UV–vis) spectroscopy, energy dispersive X-ray (EDX) spectroscopy, cyclic voltammetry (CV), and solid-state carbon-13 nuclear magnetic resonance (13C NMR) spectroscopy measurements. Furthermore, the copolymerization ratio could be controlled by selection of the oxidation potential applied for copolymerization.
A melamine cyanurate complex catalyst containing Pd(II) ions (denoted Pd/M-CA) was effective for Suzuki-Miyaura cross-coupling reactions in environmentally benign aqueous media at room temperature. The reaction conditions, such as the type of Pd species in Pd/M-CA, loading amounts of Pd, solvent, and substrate concentration, were investigated for optimization. In the presence of Pd/M-CA under the optimal conditions, cross-coupling reactions of a wide range of structurally diverse aryl halides and arylboronic acids containing functional groups proceeded smoothly to provide the corresponding products in high yields. In addition, the Pd/M-CA could be reused at least 5 times while maintaining high yields. The reduction of Pd(II) ions in Pd/M-CA to Pd(0) by NaBH4 enhanced the catalytic activity to provide a high turnover number (TON) of 17600 and turnover frequency (TOF) of 880 h−1.
Crystals consisting of the closed-ring form of 1,2-bis(3-methyl-5-phenyl-2-thienyl)perfluorocyclopentene underwent a photochemical ring-opening reaction accompanying crystal fragmentation upon irradiation with visible light. The open-ring form crystal produced by the ring-opening reaction exhibited green fluorescence, whereas open-ring form crystals produced by recrystallization exhibit orange or yellow fluorescence depending on the polymorphic forms. The fluorescence quantum yield of the photogenerated open-ring form crystal was larger than that in n-hexane. The open-ring form exhibits different fluorescence colors depending on the intermolecular interaction in different states.
We investigated the relationship between the conductivities of CeO2-ZrO2-MOx (M = Bi, Ca, Sn, Ni, Fe) solid solutions and the catalytic abilities of catalysts composed of PdO on CeO2-ZrO2-MOx/γ-Al2O3 supports. The oxide-ionic conductivities of the CeO2-ZrO2-MOx promoters increased with increasing oxygen vacancy concentrations and the electronic conductivities of these promoters were significantly enhanced by doping with Sn4+/2+, Ni3+/2+ and Fe3+/2+, all of which readily undergo valency changes. Studies of the oxygen release characteristics of CeO2-ZrO2-MOx/γ-Al2O3 samples found that the reduction temperatures obtained from hydrogen temperature programmed reduction data were primarily determined by the electronic conductivity of the promoter rather than by the oxide-ionic conductivity. However, the oxygen storage capacity of each CeO2-ZrO2-MOx/γ-Al2O3 sample was related to both the oxide-ionic and electronic conductivities. The catalytic methane oxidation activities of these materials were evidently affected by both the reduction temperature and the oxygen storage capacity. As a result, the activities of the PdO/CeO2-ZrO2-MOx/γ-Al2O3 catalysts were clearly dependent on the oxide-ionic and electronic conductivities of the CeO2-ZrO2-MOx promoters.
The magnetic field effect (MFE) on lead metal deposition from the reaction of lead(II) acetate aqueous solution and a zinc metal plate was studied. The effect depends on the lead(II) acetate concentration. By applying a 0.38 T field, the deposition yield increased by 50% and 10%, respectively, when a 0.2 M and a 0.5 M solution was used. It decreased by about 5% when a 0.1 M solution was used. The effect is explainable by Lorentz-force-induced convection. The decrease or increase of the yield is probably attributable to the change of the rate-controlling step in this inhomogeneous reaction by the change of lead(II) ion concentration.
CaAlSiN3:Eu2+ is a widely applied phosphor in white LEDs (w-LEDs) because of strong blue absorption and efficient red luminescence with high thermal quenching temperature. The good stability against thermal quenching has been well established, but the mechanism for the luminescence quenching at high temperatures has not been elucidated yet. In this report, we investigate the possibility of thermal ionization quenching by thermoluminescence (TL) and persistent luminescence techniques. In the TL glow curve by UV charging at 100 K, two broad TL glow bands were observed around 160 and 390 K. The higher TL glow band was not observed by 550 nm charging at 300 K, but it was observed by 550 nm charging at above 400 K which corresponds to the onset temperature of luminescence quenching. Because the 550 nm light excites the lowest 5d level of Eu2+, we conclude that the luminescence quenching of CaAlSiN3:Eu2+ at high temperatures is caused by the thermal ionization.
We developed a UV-curable resin (NL-SU1) suitable for screen printing with laser-drilled polyimide masks and reverse-tone nanoimprint lithography. The viscosity of the UV-curable resin composed of two bisphenol A-based monomers was adjusted to 11.0 Pa·s for the screen printing process. It was determined by photo-differential scanning calorimetry that photoinitiator Irgacure 369 was suitable for high methacrylate consumption in UV curing. The UV-curable resin after curing could be used as a top-coated resist layer on another imprinted resist layer because of its sufficient contrast in oxygen reactive ion etching and argon ion milling. We demonstrated a method for reverse-tone lithography in a print–and-imprint method to fabricate 20-nm-thick and 50-nm-linewide Au split-ring resonator arrays.
The catalytic enantioselective synthesis of planar chiral cyclophanes has been achieved by two types of transition-metal catalysis: (1) enantioselective construction of aromatic rings by transition-metal-catalyzed [2+2+2] cycloaddition reactions; (2) enantioselective construction of ansa chains by transition-metal-catalyzed coupling reactions. The former approach has been achieved by the cationic rhodium(I)/H8-BINAP complex-catalyzed enantioselective intramolecular [2+2+2] cycloaddition of triynes, which afforded planar chiral dioxa–metacyclophanes with high ee values, although the yields were low. Planar chiral carba–paracyclophanes could also be synthesized with high yields and ee values by the cationic rhodium(I)/BDPP complex-catalyzed enantioselective intermolecular [2+2+2] cycloaddition of cyclic diynes with monoynes. On the other hand, the latter approach was achieved by the cationic rhodium(I)/BINAPHANE or palladium(II)/BINAP complex-catalyzed double C–S bond formation between dithiols and 1,4-bis(bromomethyl)benzenes, which afforded planar chiral dithia–paracyclophanes and dithia[3.3]paracyclophanes with varying yields and ee values.
In this work, we have prepared alumina-embedded mesoporous silica and investigated their molybdenum (Mo) adsorption properties. To synthesize such materials, mesoporous silica particles were firstly synthesized via a soft-templated approach followed by the introduction of aluminium butoxide into the mesopores, which was converted into alumina by heat treatment at high temperatures. The obtained alumina-embedded mesoporous silica samples (Alx-MPS) were characterized by low- and wide-angle X-ray diffractions, nitrogen adsorption-desorption isotherms, and transmission electron microscopy. The effects of Al/Si ratios and calcination temperature on their Mo adsorption properties were also carefully investigated by using the batch method. The experimental results showed the following trend in Mo adsorption capacity in relation to the calcination temperature: 750 °C > 600 °C > 900 °C > 1050 °C and Al/Si molar ratio: Al0.1-MPS < Al0.3-MPS < Al0.5-MPS < Al0.6-MPS.
The effect of concentration of two anionic surfactants sodium 1-octanesulfonate and sodium 1-decanesulfonate in the temperature range 288–318 K on the kinetics and mechanism of electroreduction of Zn2+ ions was studied using electrochemical impedance spectroscopy (eis) and other electrochemical methods. It was found that the process of electroreduction proceeds in two steps. To describe the mechanism of Zn2+ amalgamation, the Fawcett’s models were considered: CE (chemical step C, electron transfer step E), IE (ion transfer step I, electron transfer step E) and IA (ion transfer step I, adsorption step A). The results of theoretical investigations suggest that the IE model is the most probable mechanism of the process. Both surfactants were found to exert a catalytic effect on the analyzed electrode process. The accelerating abilities of the surfactants were found to increase with the growth of the length of their hydrocarbon chain and with the increase of temperature. The observations concerning the mechanism of the electrode reaction and its acceleration caused by surfactants were confirmed by the parameters calculated from temperature dependencies.
Rhodium-catalyzed alkylation reactions of C-H bonds (hydroarylation) in aromatic amides that contain an 8-aminoquinoline as a directing group with alkenes are discussed. Various alkenes, including acrylic esters, styrenes, α,β-unsaturated butyrolactones, dihydrofurans, maleimides, and norbornene derivatives are applicable to this C-H alkylation. The reaction with norbornene gives unusual endo-hydroarylation products in a high degree of selectivity. The use of a carboxylic acid as an additive dramatically increases both the reactivity and the selectivity of the reaction. The results of deuterium-labeling experiments suggest that hydrometalation or carbometalation, which are commonly accepted mechanisms for C-H alkylation reactions, are not involved. Instead, the reaction appears to proceed through a rhodium carbene intermediate generated from the alkene.
Reports on the room temperature phosphorescence of metal-free organic crystals have been surging in the past few years. Together with interests in the rare phenomenon, these compounds have attracted attention for such potential applications as bio-imaging probes, oxygen sensors, and organic light-emitting diodes. For common organic compounds, phosphorescence is the emission from a triplet excited state, which is usually produced from a singlet excited state through intersystem crossing, a forbidden spin-flip of an electron. The mechanism of the forbidden process is the key to understanding such rare phenomenon and designing new phosphorescence materials. In this account, we make commentaries on the main intersystem crossing mechanisms proposed to date of the room temperature phosphorescence of heavy-atom-free, crystalline organic compounds, focusing on our own findings.
5,10,15,20-Tetrakis(4-(α-d-mannopyranosylthio)-2,3,5,6-tetrafluorophenyl)-2,3-(methano(N-methyl)iminomethano)chlorin (H2TFPC-SMan) has been prepared and characterized by 1H and 19F NMR and UV-vis spectroscopies, MALDI-TOF mass spectrometry, and elemental analysis.
H2TFPC-SMan generates singlet oxygen (1O2) upon light irradiation. The value of the relative magnitude of the 1O2-generating ability of H2TFPC-SMan is comparable to that of 5,10,15,20-tetrakis(4-(β-d-glucopyranosylthio)-2,3,5,6-tetrafluorophenyl)-2,3-(methano(N-methyl)iminomethano)chlorin (H2TFPC-SGlc). The dark and photocytotoxicity of H2TFPC-SMan and H2TFPC-SGlc were tested in HeLa cells. These compounds showed no cytotoxicity in the dark. Upon photoirradiation, these compounds killed almost all of the cells in the region of a 1 to 2 µM concentration. The photocytotoxicity of the compounds completely disappeared in the concentration region of 0 to 0.1 µM. The photocytotoxicity of H2TFPC-SMan is significantly higher than that of H2TFPC-SGlc in the concentration range from 0.2 to less than 1 µM. The cellular uptake of H2TFPC-SMan in HeLa cells was estimated in terms of fluorescence intensity from each HeLa cell. The cellular uptake of H2TFPC-SMan is significantly higher than that of H2TFPC-SGlc at a concentration of 0.5 µM. These results are consistent with the experimental observation that the photocytotoxicity of H2TFPC-SMan is significantly higher than that of H2TFPC-SGlc in a concentration range from 0.2 to less than 1 µM.
A new type of photoswitchable fluorescent diarylethenes, which have no fluorophore unit but emit strong fluorescence (Φf ∼ 0.9) in the closed-ring isomers, has been developed. They are sulfone derivatives of 1,2-bis(2-alkyl-4-methyl-5-phenyl-3-thienyl)perfluorocyclopentenes and 1,2-bis(2-alkyl-1-benzothiophen-3-yl)perfluorocyclopentenes. By chemical modifications of the structures their switching response was tuned to meet the requirements for super-resolution fluorescence microscopies. The water-soluble derivatives have been successfully applied to acquire super-resolution bioimages using a single-wavelength visible beam.
Transition-metal-catalyzed coordination–insertion polymerization of olefins is an indispensable tool in polymer synthesis. When polar monomers with polar functional groups are employed, however, the catalysts are often deactivated owing to side reactions such as σ-coordination and β-elimination of the functional group. Nevertheless, recent progress in late transition metal catalysis has enabled the synthesis of many types of functional polymers from polar monomers through coordination–insertion polymerization methods. This account describes our achievements in the palladium-catalyzed coordination–insertion (co)polymerization of polar monomers for the syntheses of a variety of functional polymers, ranging from functionalized polyolefins via olefin/polar monomer copolymerization to o-arylene-containing polymers via formal aryne polymerization.
The recent advances in the use of rigid polynorbornene or polycyclobutene as template for the synthesis of different polymers with well-defined degree of polymerization and narrow polydispersity are reviewed. Polynorbornene and polycyclobutene templates containing fused N-arylpyrrolidene pendants are synthesized by ruthenium or molybdenum-catalyzed ring opening metathesis polymerization (ROMP) of the corresponding monomers. Since these polymerizations are living, the templates thus have well-defined degree of polymerization and narrow polydispersity. Monomers are linked to the template polymer via ester linkage. After polymerization and hydrolysis, the poly-carboxylic acid template can easily be separated from the neutral polyalcohol daughter polymer.
Various magnetic criteria of aromaticity have been proposed so far, because they are easily calculated and applicable to a variety of cyclic π-systems. Many researchers, however, are reluctant to accept all or some of them. Our graph theory of ring-current diamagnetism revealed serious flaws in familiar magnetic criteria of aromaticity. Physically meaningful information on aromaticity can nevertheless be extracted from the ring-current diamagnetism. In particular, magnetic resonance energy (MRE), derived from the ring-current diamagnetic susceptibility, is interpretable as a kind of aromatic stabilization energy (ASE) and helps in consistently interpreting energetic and magnetic criteria of aromaticity. MRE and related quantities can be determined without reference to any hypothetical polyene-like structure but with a reasonable assumption that, when a magnetic field is applied to a cyclic π-system, a current is induced in each circuit in proportion to the ASE arising from the circuit. Unlike other conventional magnetic indexes, they are independent of the size and shape of the π-system.
ATP and ADP are the major energy source in metabolism of cells, and furthermore ATP works as an important extracellular signaling material. ATP bioimaging is required to understand their metabolism. In this paper, a label-free ATP/ADP image sensor was fabricated using a 128 × 128 (16 k) pixel array semiconductor CCD-type pH image sensor and Apyrase. The principle is based on measuring protons produced by the enzyme reaction between Apyrase and ATP or ADP. In order to put a uniform potential response of the sensor into practice, two different methods, (3-APTES and CEST), which chemically fixed N-terminal of Apyrase with the sensor were examined. The sensor modified by the CEST method had a quite clean surface microscopically and demonstrated a fine real-time image monitoring the ATP concentration. The potential response of the image sensor was characterized; effect of buffer solution, calibration curves of ATP and ADP, durability, the limit of detection (LOD) for ATP, and the response of time. The potential distribution for effective pixels to ATP concentration was narrow, single and symmetrical. Due to 16 K sensing pixels finely responding to ATP concentration uniformly, the LOD of ATP concentration (10 µM) was exactly determined with a statistical treatment.
Herein, we report the green synthesis of magnetite (Fe3O4) nanostructures (including flower-like nanosheets and cube-like particles) with large surface areas ranging from 127 to 318 m2 g−1 from naturally available iron sands using a facile sonochemical method, with the assistance of polyethylene glycol (PEG 6000). The X-ray diffraction (XRD) results reveal that the Fe3O4 nanostructures obtained from these iron sands are of good purity and crystallinity and are polycrystalline with an inverse cubic spinel structure. The increased addition of PEG 6000 from 5 to 25% v/v is found to result in larger crystallite size and improved crystallinity. Furthermore, the Fe3O4 nanostructures synthesized by our proposed method have a tendency to form flower-like structures composed of thin nanosheets when the amount of PEG 6000 is low (5–10% v/v), although their morphology gradually changes to cube-like particles at 15% PEG, before finally being converted to spherical nanoparticles with relatively good dispersity at high PEG contents (above 15%). More importantly, the specific surface area of the obtained Fe3O4 nanostructures decreases with increased addition of PEG due to the increased agglomeration of the particles. The magnetic properties characterization of the as-prepared Fe3O4 samples via vibrating sample magnetometer revealed that they exhibit superparamagnetism at room temperature and that their saturation magnetization values are strongly affected by the crystallite size of the Fe3O4 phase as Fe3O4 nanoparticles with larger crystallite size exhibit higher saturation magnetization (Ms) values. The presented work may encourage the use of naturally available resources rather than laboratory-made chemical reagents for the synthesis of iron oxide and other metal oxide nanostructures in the future.