Iron–Oxalato Framework with One‐Dimensional Open Channels for Electrochemical Sodium‐Ion Intercalation

Discovery of a new class of ion intercalation compounds is highly desirable due to its relevance to various electrochemical devices, such as batteries. Herein, we present a new iron–oxalato open framework, which showed reversible Na⁺ intercalation/extraction. The hydrothermally synthesized K₄Na₂[Fe(C₂O₄)₂]₃ ? 2 H₂O possesses one‐dimensional open channels in the oxalato‐bridged network, providing ion accessibility up to two Na⁺ per the formula unit. The detailed studies on the structural and electronic states revealed that the framework exhibited a solid solution state almost entirely during Na⁺ intercalation/extraction associated with the reversible redox of Fe. The present work demonstrates possibilities of the oxalato frameworks as tunable and robust ion intercalation electrode materials for various device applications.     

Laplace transform impedance analysis in the two-phase coexistence reaction of spinel Li1 + x Mn2O4 positive electrode

Journal of Solid State Electrochemistry - We demonstrate the Laplace transform (LT) impedance technique for measuring electrochemical lithiation and delithiation in the two-phase system of spinel...     

Rhenium complex-catalyzed acylative cleavage of ethers with acyl chlorides

It was found that rhenium complex was an efficient catalyst for the acylative cleavage of C-O bond of ethers with acyl chlorides. When acyclic ethers were allowed to react with acyl chlorides in the presence of a catalytic amount of ReBr(CO)₅, acylative cleavage of C-O bond of acyclic ethers smoothly proceeded to give the corresponding esters in moderate to good yields. Similarly, cyclic ethers were acylative cleaved by acyl chlorides to give the corresponding chloro substituted esters in good yields by the use of Re₂O₇ catalyst.     

Synthesis of 4-unsubstituted dihydropyrimidines. Nucleophilic substitution at position-2 of dihydropyrimidines

Synthesis of novel 4-unsubstituted dihydropyrimidines (DPs) was performed. Subsequently, a variety of 4-unsubstituted 1,4(3,4)-DPs with amino moieties at position-2 were obtained in excellent yields by activation of position-2 owing to regioselective alkoxycarbonylation at position-3 of the DP skeleton. 3-Oxo-2-phenyl-2,3,5,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrimidine was obtained using phenylhydrazine instead of amines. Individual tautomers of 1,4(3,4)-DP were observed in the ¹H NMR spectra of one derivative depending on temperature and concentration. On the other hand, only 1,4-DP was found in the solid state by single-crystal X-ray crystallography.     

Importance of sialic acid residues illuminated by live animal imaging using phosphorylcholine self-assembled monolayer-coated quantum dots

Glycans are expected to be one of the potential signal molecules for controlling drug targeting/delivery or long-term circulation of biopharmaceuticals. However, the effect of the carbohydrates of artificially glycosylated derivatives on in vivo dynamic distribution profiles after intravenous injection of model animals remains unclear due to the lack of standardized methodology and a suitable platform. We report herein an efficient and versatile method for the preparation of multifunctional quantum dots (QDs) displaying common synthetic glycosides with excellent solubility and long-term stability in aqueous solution without loss of quantum yields. Combined use of an aminooxy-terminated thiol derivative, 11,11'-dithio bis[undec-11-yl 12-(aminooxyacetyl)amino hexa(ethyleneglycol)], and a phosphorylcholine derivative, 11-mercaptoundecylphosphorylcholine, provided QDs with novel functions for the chemical ligation of ketone-functionalized compounds and the prevention of nonspecific protein adsorption concurrently. In vivo near-infrared (NIR) fluorescence imaging of phosphorylcholine self-assembled monolayer (SAM)-coated QDs displaying various simple sugars (glyco-PC-QDs) after administration into the tail vein of the mouse revealed that distinct long-term delocalization over 2 h can be achieved in cases of QDs modified with α-sialic acid residue (Neu5Ac-PC-QDs) and control PC-QDs, while QDs bearing other common sugars, such as α-glucose (Glc-PC-QDs), α-mannose (Man-PC-QDs), α-fucose (Fuc-PC-QDs), lactose (Lac-PC-QDs), β-glucuronic acid (GlcA-PC-QDs), N-acetyl-β-D-glucosamine (GlcNAc-PC-QDs), and N-acetyl-β-D-galactosamine (GalNAc-PC-QDs) residues, accumulated rapidly (5-10 min) in the liver. Sequential enzymatic modifications of GlcNAc-PC-QDs gave Galβ1,4GlcNAc-PC-QDs (LacNAc-PC-QDs), Galβ1,4(Fucα1,3)GlcNAc-PC-QDs (Le(x)-PC-QDs), Neu5Acα2,3Galβ1,4GlcNAc-PC-QDs (sialyl LacNAc-PC-QDs), and Neu5Acα2,3Galβ1,4(Fucα1,3)GlcNAc-PC-QDs (sialyl Le(x)-PC-QDs) in quantitative yield as monitored by direct matrix-assisted laser desorption ionization time-of-flight mass spectrometry analyses. Live animal imaging uncovered for the first time that Le(x)-PC-QDs also distributed rapidly in the liver after intravenous injection and almost quenched over 1 h in similar profiles to those of LacNAc-PC-QDs and Lac-PC-QDs. On the other hand, sialyl LacNAc-PC-QDs and sialyl Le(x)-PC-QDs were still retained stably in the whole body after 2 h, while they showed significantly different in vivo dynamics in the tissue distribution, suggesting that structure/sequence of the neighboring sugar residues in the individual sialyl oligosaccharides might influence the final organ-specific distribution. The present results clearly visualize the evidence of an essential role of the terminal sialic acid residue(s) for achieving prolonged in vivo lifetime and biodistribution of various glyco-PC-QDs as a novel class of functional platforms for nanomaterial-based drug targeting/delivery. A standardized protocol using multifunctional PC-QDs should facilitate live animal imaging of ligand-displayed QDs using versatile NIR fluorescence photometry without influence of size-dependent accumulation/excretion pathway for nanoparticles (e.g., viruses) >10 nm in hydrodynamic diameter by the liver.     

Kinetics of hydrogen bonding between anthracene urea derivatives and anions in the excited state

Urea compounds are useful anion sensors due to their hydrogen-bonding capabilities. We investigated the emissive properties of complexes consisting of urea-anthracene (nPUA, n = 1, 2) host compounds and acetate anions held as guests through intermolecular hydrogen bonding. The kinetics of a new emission band formed by conformational changes in the excited singlet state were revealed. The new band is thought to arise from a charge-transfer interaction between the anthracene and urea moieties after intermolecular hydrogen-bond reconfiguration in the excited state, with rate constants of 2.4 × 10(9) and 4.0 × 10(7) s(-1) for 1PUA and 2PUA, respectively.     

Role of base in the formation of silver nanoparticles synthesized using sodium acrylate as a dual reducing and encapsulating agent

The formation mechanism of Ag nanoparticles (NPs) synthesized with a wet-chemical reduction method using sodium acrylate as a dual reducing and capping agent was investigated with various analytical techniques. The time course of the state of the reaction solution was investigated using UV-vis and XAFS spectroscopies which showed that the NP formation rate increased with increasing concentration of sodium hydroxide (NaOH). The detailed kinetic analyses reveal that both the reduction rate of Ag ions and the nucleation rate of Ag NPs are dramatically increased with increasing NaOH concentration. XANES analyses imply that another reaction pathway via alternative Ag(+) species, such as Ag(OH)(x), was developed in the presence of NaOH. Consequently, NaOH is found to play an important role not only in creating specific intermediates in the reduction of Ag(+) to Ag(0), but also in accelerating the reduction and nucleation rates by enhancing the oxidation of sodium acrylate, thereby increasing the rate of formation of the Ag NPs.     

Optical fibers and fiber dispersion compensators for high-speed optical communication

In order to meet the requirements necessary for advanced optical fiber transmission schemes that enable larger transmission capacity, higher efficiency and/or lower transmission costs per bit, optical fiber technologies are still evolving toward ultimate performance. Recent developmental activities have realized a number of improved performance optical fibers, such as ultra-low loss or ultra-low nonlinearity fibers and various types of dispersion-modified fibers. Fiber-based dispersion compensators or dispersion compensating fibers have also become one of the most essential optical components that support high-speed large capacity optical transmission. Very recently, the dispersion compensating fibers have further evolved into dispersion-managed optical transmission lines, which are now being actually deployed in transoceanic submarine optical cable networks.