Synthesis of [1]rotaxane via covalent bond formation and its unique fluorescent response by energy transfer in the presence of lithium ion

Although there have been a lot of reports on the synthesis and properties of [n]rotaxanes (mainly n = 2), only a few reports on the synthesis of [1]rotaxane has been published by V?gtle's group and others (see ref 5). Generally speaking, [1]rotaxane might be expected to exhibit properties different from other rotaxanes, because the rotor and the axle in the [1]rotaxane is bound covalently and closely. We report on a novel method to make [1]rotaxanes via covalent bond formation from a macrocyclic compound. That is, we first prepared a bicyclic compound from macrocycle and then proceeded to [1]rotaxane by aminolysis. This is the first synthetic example of preparation of [1]rotaxane via covalent bond formation, not utilizing weak interactions such as hydrogen bonding, charge transfer, via metal complexation, etc. This method might provide a powerful and new tool for construction of [1]rotaxane as a new supramolecular system. In addition, we investigated energy transfer from rotor to axle using [1]rotaxane that we prepared. Energy transfer occurred perfectly from the naphthalene ring of the rotor to the anthracene ring of the axle. We found also that only lithium ion among alkali ions can drastically enhance the fluorescence intensity. This finding could be applicable to ion-sensing systems, switching devices, and so on.     

Improvement of stability of a Fe/Mg/Al2O3 catalyst for the decomposition of methane in the presence of O2/CO2

The stability of an Fe/Al₂O₃ catalyst in the methane decomposition in the presence of O₂/CO₂ was found to be improved by the addition of Mg into the catalyst (Mg/Fe=1/1 wt ratio), probably due to suppression of carbon deposition even under CH₄/ O₂/CO₂ (80/10/5 vol. ratio) conditions. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis of supramolecular boron complex with anthryl groups exhibiting specific optical response for chloride ion

Supramolecular boron complex having plural hydrogen bonding sites and anthracene moieties was synthesized and showed an excimer emission selectively accompanied with capture of chloride ions.     

Urinary metabolic profile of phenylketonuria in patients receiving total parenteral nutrition and medication

Nutrition and drugs are main environmental factors that affect metabolism. We performed metabolomics of urine from an 8‐year‐old patient (case 1) with epilepsy and an 11‐year‐old patient (case 2) with malignant lymphoma who was being treated with methotrexate. Both patients were receiving total parenteral nutrition (TPN). We used our diagnostic procedure consisting of urease pretreatment, partial adoption of stable isotope dilution, gas chromatography/mass spectrometry (GC/MS) measurement and target analysis for 200 analytes including organic acids and amino acids. Surprisingly, their metabolic profiles were identical to that of phenylketonuria. The neopterin level was markedly above normal in case 1, and both neopterin and biopterin were significantly above normal in case 2. Mutation analysis of genomic DNA from case 1 showed neither homozygosity nor heterozygosity for phenylalanine hydroxylase deficiency. The metabolic profiles of both cases were normal when they were not receiving TPN. TPN is presently prohibited for individuals who have inherited disorders that affect amino acid metabolism. Although the Phe content of the TPN was not the sole cause of the PKU profile, its effect, combined with other factors, e.g. specific medication or possibly underlying diseases, led to this metabolic abnormality. The present study suggests that GC/MS‐based metabolomics by target analysis could be important for assuring the safety of the treatments for patients receiving both TPN and methotrexate. Metabolomic profiling, both before and during TPN, is useful for determining the optimal nutritional formula not only for neonates, but also for young children who are known heterozygotes for metabolic disorders or whose status is unknown. Copyright © 2009 John Wiley & Sons, Ltd.     

Efficient 340-nm light generation by a ridge-type waveguide in a first-order periodically poled MgO:LiNbO3

Quasi-phase-matched (QPM) UV second-harmonic generation (SHG) in a periodically poled MgO:LiNbO3 waveguide is presented. A ridge-type waveguide with high nonlinearity and strong resistance to photorefractive damage was achieved by use of an ultraprecision machining technique. By use of this waveguide in 1.4-microm periodically poled MgO:LiNbO3, a first-order QPM SHG device for 340-nm UV radiation was demonstrated. In a single-pass configuration, continuous-wave 22.4-mW UV light was generated for a fundamental power of 81 mW, corresponding to a normalized conversion efficiency of 340%/W.     

Structural kinetics studies on phase transitions of the Bi UPD layer between the (2 x 2) and (p x square root[3]) structures using surface X-ray diffraction

The kinetics of the phase transition between the (2 x 2) and (p x square root[3])-Bi structures on Au(111) was investigated using electrochemical methods and time-resolved surface X-ray diffraction. The temporal changes in the current value and the diffracted X-ray intensity that originated from the (2 x 2)-Bi overlayer were monitored during the phase transitions at various over-potentials. The phase transition models and kinetics parameters were deduced from each of the current and X-ray intensity transient curves. We also carried out comparative studies of the phase transition from the structural and electrochemical points of view. For the (p x square root[3]) --> (2 x 2) phase transition, the phase transition models determined by the X-ray and electrochemical measurements were a surface-diffusion controlled instantaneous nucleation-growth process and a Langmuir process, respectively. For the reverse transition, the phase transition models determined by X-ray and electrochemical measurements were a Langmuir adsorption process and a surface diffusion controlled nucleation-growth process, respectively. Our results revealed that the current transient curve does not always reflect the phase transition model in both cases and suggest that a structural analysis is fundamental in the phase transition studies. The disagreements between the phase transition models and their mechanisms are discussed.     

Laser fragmentation of water-suspended gold flakes via spherical submicroparticles to fine nanoparticles

By nanosecond, 532-nm laser irradiation typically at approximately 1 J/(cm2 pulse), water-suspended thin gold flakes, 0.1-0.2-microm thick but more than 10-microm across, were efficiently fragmented in a unique two-step mode, as evidenced by the in situ extinction spectra taken as a function of the laser irradiation time. The initial main photoproducts were spherical gold particles in the submicrometer regime. Their ensuing laser fragmentation in oxygen-free water environment generated stable, negatively charged, fine nanoparticles less than 10 nm in diameter, characterized by a considerably weak and blue-shifted plasmon band. The Mie theory can reproduce these distinct spectral features of the fine nanoparticles as well as the scattering-dominated extinction spectra of the submicroparticles. The submicroparticle to nanoparticle conversion seemed most likely to be a single-pulse event, not leaving any larger intermediate nanoparticles in the suspension. Oxygen, as an effective electron acceptor, strongly affected the stability of the negatively charged nanoparticles, promoting their quasi-reversible or irreversible agglomeration. From the estimated balance between the absorbed laser energy and the energies for the relevant particles to produce a high-temperature molten state, possible fragmentation mechanisms are discussed.