Induced Fitting and Polarization of a Bromine Molecule in an Electrophilic Inorganic Molecular Cavity and Its Bromination Reactivity.

Dodecavanadate, [V12 O32 ]4- (V12), possesses a 4.4 Šcavity entrance, and the cavity shows unique electrophilicity. Owing to the high polarizability, Br2 was inserted into V12, inducing the inversion of one of the VO5 square pyramids to form [V12 O32 (Br2 )]4- (V12(Br2)). The inserted Br2 molecule was polarized and showed a peak at 185 cm-1 in the IR spectrum. The reaction of V12(Br2) and toluene yielded bromination of toluene at the ring, showing the electrophilicity of the inserted Br2 molecule. Compound V12(Br2) also reacted with propane, n-butane, and n-pentane to give brominated alkanes. Bromination with V12(Br2) showed high selectivity for 3-bromopentane (64 %) among the monobromopentane products and preferred threo isomer among 2-,3-dibromobutane and 2,3-dibromopenane. The unique inorganic cavity traps Br2 leading the polarization of the diatomic molecule. Owing to its new reaction field, the trapped Br2 shows selective functionalization of alkanes.

Development of dispersive XAFS system for analysis of time-resolved spatial distribution of electrode reaction.

Apparatus for a technique based on the dispersive optics of X-ray absorption fine structure (XAFS) has been developed at beamline BL-5 of the Synchrotron Radiation Center of Ritsumeikan University. The vertical axis of the cross section of the synchrotron light is used to disperse the X-ray energy using a cylindrical polychromator and the horizontal axis is used for the spatially resolved analysis with a pixel array detector. The vertically dispersive XAFS (VDXAFS) instrument was designed to analyze the dynamic changeover of the inhomogeneous electrode reaction of secondary batteries. The line-shaped X-ray beam is transmitted through the electrode sample, and then the dispersed transmitted X-rays are detected by a two-dimensional detector. An array of XAFS spectra in the linear footprint of the transmitted X-ray on the sample is obtained with the time resolution of the repetition frequency of the detector. Sequential measurements of the space-resolved XAFS data are possible with the VDXAFS instrument. The time and spatial resolutions of the VDXAFS instrument depend on the flux density of the available X-ray beam and the size of the light source, and they were estimated as 1 s and 100 µm, respectively. The electrode reaction of the LiFePO4 lithium ion battery was analyzed during the constant current charging process and during the charging process after potential jumping.

Development of a two-dimensional imaging system of X-ray absorption fine structure.

A two-dimensional imaging system of X-ray absorption fine structure (XAFS) has been developed at beamline BL-4 of the Synchrotron Radiation Center of Ritsumeikan University. The system mainly consists of an ionization chamber for I(0) measurement, a sample stage, and a two-dimensional complementary metal oxide semiconductor (CMOS) image sensor for measuring the transmitted X-ray intensity. The X-ray energy shift in the vertical direction, which originates from the vertical divergence of the X-ray beam on the monochromator surface, is corrected by considering the geometrical configuration of the monochromator. This energy correction improves the energy resolution of the XAFS spectrum because each pixel in the CMOS detector has a very small vertical acceptance of ∼0.5 µrad. A data analysis system has also been developed to automatically determine the energy of the absorption edge. This allows the chemical species to be mapped based on the XANES feature over a wide area of 4.8 mm (H) × 3.6 mm (V) with a resolution of 10 µm × 10 µm. The system has been applied to the chemical state mapping of the Mn species in a LiMn(2)O(4) cathode. The heterogeneous distribution of the Mn oxidation state is demonstrated and is considered to relate to the slow delocalization of Li(+)-defect sites in the spinel crystal structure. The two-dimensional-imaging XAFS system is expected to be a powerful tool for analyzing the spatial distributions of chemical species in many heterogeneous materials such as battery electrodes.

Formation and oxidation mechanisms of Pd-Zn nanoparticles on a ZnO supported Pd catalyst studied by in situ time-resolved QXAFS and DXAFS.

Formation and oxidation processes of PdZn nanoparticles on ZnO were successfully observed by means of in situ time-resolved X-ray absorption fine structure spectroscopy (XAFS), and the analysis of data on near-edge (XANES) and extended (EXAFS) structures revealed detailed changes in Pd during both processes. PdZn nanoparticles were formed on ZnO through a two-step scheme under a hydrogen atmosphere. The first process was the formation of metallic Pd nanoparticles, which was quickly finished within 1 s. The second process was the formation of PdZn nanoparticles, which took several tens of minutes. Oxidation of the PdZn nanoparticles also consisted of two processes. Zn atoms were oxidized prior to Pd atoms and the metallic Pd nanoparticles surrounded by ZnO were formed afterwards. Oxidation of the metallic Pd nanoparticles was scarce and very slow. According to the results of kinetic analyses, the metallic Pd surrounded by ZnO was a stable species under the oxidative atmosphere.

In situ time-resolved DXAFS for the determination of kinetics of structural changes of H-ZSM-5-supported active Re-cluster catalyst in the direct phenol synthesis from benzene and O2.

Dynamic structural changes and their kinetics of a Re(10)-cluster catalyst in the direct phenol synthesis from benzene and O(2) were investigated by in situ time-resolved Re L(III)-edge energy-dispersive XAFS (DXAFS). We have successfully monitored the structural transformation of active Re(10) clusters to inactive Re monomers in the course of the selective oxidation of benzene with O(2) on the catalyst by the DXAFS technique in a real time. The results obtained suggested that the Re(10) cluster transformed directly to the Re monomers, which showed first order kinetics with respect to the quantity of Re(10) clusters. The absence of undesirable intermediate structures with low phenol selectivity during the structural transformation may be an advantageous issue for the high phenol selectivity of 93.9% at 9.9% conversion in a pulse reaction and 87.7% at 5.8% conversion in a steady-state reaction on the Re(10)-cluster catalyst. The reactant benzene inhibited the unfavorable structural transformation of the Re(10) cluster to the Re monomers during the selective benzene oxidation to phenol.

Development of Simultaneous Measurement System for X-ray Absorption Spectra at Two Absorption Edges.

Dispersive X-ray absorption fine structure (DXAFS) spectroscopy is a versatile measurement technique for analyzing chemical reactions in real time. We have developed a novel time-resolved DXAFS instrument based on two polychromators and a wide-range position-sensitive detector that permits direct observation of the synergistic effects of two elements. This system enables simultaneous acquisition of the X-ray absorption spectra for two different elements without any mechanical movement of the X-ray optics. The developed system was successfully applied to monitor both the synthesis of a Ni-Cu bimetallic catalyst, which revealed that the reduction of Ni occurred at a higher temperature than that of Cu, and the charge-discharge processes of a LixNi0.5Mn1.5O4-based lithium-ion battery, which demonstrated that the redox reactions of Ni and Mn occurred sequentially at specific electrode potentials.

Primary osteosarcoma of the lung: a case report and review of the literature.

Primary osteosarcoma of the lung is exceedingly rare. A 72-year-old man was admitted to our hospital; a primary osteosarcoma of the lung was diagnosed following computed tomography-guided needle biopsy. He died of rapidly progressing respiratory insufficiency without effective treatment seven months after the onset of symptoms. Macroscopic findings at autopsy showed typical histologic features of osteosarcoma without any bony lesion. Here we present a rare case and review the clinicopathological features of 20 previously reported cases.

Water exchange dynamics of lithium(I) ion in aqueous solution.

The water exchange dynamics of the fourfold coordinated first hydration shell of the lithium(I) ion was studied by both direct and umbrella sampling QM/MM-MD and classical MD simulations. The structural changes and energetics accompanying the activation process are discussed. The overall exchange rate constant was found to be k(ex) = 5.8 x 10(9) s(-1) from classical MD simulations. QM/MM-MD umbrella sampling simulations predict an exchange rate constant of k(TST) = 1.01 x 10(10) s(-1) as obtained from classical transition-state theory. First-shell ligands exchange preferably via an associatively activated mode.

Ionic Conduction in Lithium Ion Battery Composite Electrode Governs Cross-sectional Reaction Distribution.

Composite electrodes containing active materials, carbon and binder are widely used in lithium-ion batteries. Since the electrode reaction occurs preferentially in regions with lower resistance, reaction distribution can be happened within composite electrodes. We investigate the relationship between the reaction distribution with depth direction and electronic/ionic conductivity in composite electrodes with changing electrode porosities. Two dimensional X-ray absorption spectroscopy shows that the reaction distribution is happened in lower porosity electrodes. Our developed 6-probe method can measure electronic/ionic conductivity in composite electrodes. The ionic conductivity is decreased for lower porosity electrodes, which governs the reaction distribution of composite electrodes and their performances.

Formation and Deprotonation Kinetics of the Sitting-Atop Complex of Copper(II) Ion with 5,10,15,20-Tetraphenylporphyrin Relevant to the Porphyrin Metalation Mechanism. Structure of Copper(II)-Pyridine Complexes in Acetonitrile As Determined by EXAFS Spectroscopy.

The formation of a sitting-atop (SAT) complex of Cu(II) ion with 5,10,15,20-tetraphenylporphyrin (H(2)tpp) in acetonitrile has been observed, and the kinetic parameters for the formation were determined as follows: k(S0) = (3.6 +/- 0.1) x 10(5) mol(-)(1) dm(3) s(-)(1) at 25.0 degrees C, DeltaH(S0)() = 56 +/- 5 kJ mol(-)(1), and DeltaS(S0)() = 46 +/- 19 J mol(-)(1) K(-)(1). The (1)H NMR spectrum of the SAT complex (Cu(H(2)tpp)(2+)) indicated that two pyrrolenine nitrogens coordinate to the Cu(II) ion and that two protons bound to the pyrrole nitrogens remain. The protons were abstracted by the addition of pyridine (py) as the Brønsted base to give the Cu(tpp) metalloporphyrin. In the presence of py, the product for the reaction of the Cu(II) ion with H(2)tpp was Cu(tpp) instead of the SAT complex. The observed conditional rates for the formation of Cu(H(2)tpp)(2+) and Cu(tpp) were interpreted by the contribution of Cu(2+), Cu(py)(2+), and Cu(py)(2)(2+) species, and the second-order rate constants of the SAT complex formation were k(S1) = (3.5 +/- 0.3) x 10(4) mol(-)(1) dm(3) s(-)(1) for Cu(py)(2+) and k(S2) = 90 +/- 2 mol(-)(1) dm(3) s(-)(1) for Cu(py)(2)(2+). Deprotonation rates were measured by following the reaction between the SAT complex and py as a function of the py concentration, and the second-order rate constant was determined to be (2.3 +/- 0.1) x 10(2) mol(-)(1) dm(3) s(-)(1). The present kinetic results have indicated that the SAT complex exists during the course of the metalation process and that the SAT complex formation is a rate-determining step.

Reevaluation of donor number using titration calorimetry.

Many empirical parameters have been suggested to measure solvent effects in chemical reactions. Gutmann's donor number has been a successful parameter to quantify the electron-donating property of the solvent molecule; it is defined as the enthalpy change of the addition reaction of solvent molecule to SbCl(5) in 1,2-dichloroethane. Calorimetric measurements can be applied to determine the quantity. Because the existence of water is critical for reactions in organic solvents, we have analyzed the enthalpy change using the titration calorimetry while considering the complexation with water. The determined donor numbers of formamide, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and 1,1,3,3-tetramethylurea (TMU) are 22.4, 26.5, 30.0, and 40.4, respectively. The values of DMF and DMSO are in perfect agreement with those of Gutmann. A reliable value for TMU is obtained for the first time on the basis of the enthalpy change for the addition reaction.

Chlorides behavior in raw fly ash washing experiments.

Chloride in fly ash from municipal solid waste incinerators (MSWIs) is one of the obstructive substances in recycling fly ash as building materials. As a result, we have to understand the behavior of chlorides in recycling process, such as washing. In this study, we used X-ray absorption near edge structure (XANES) and X-ray diffraction (XRD) to study the chloride behavior in washed residue of raw fly ash (RFA). We found that a combination of XRD and XANES, which is to use XRD to identify the situation of some compounds first and then process XANES data, was an effective way to explain the chlorides behavior in washing process. Approximately 15% of the chlorine in RFA was in the form of NaCl, 10% was in the form of KCl, 51% was CaCl(2), and the remainder was in the form of Friedel's salt. In washing experiments not only the mole percentage but also the amount of soluble chlorides including NaCl, KCl and CaCl(2) decreases quickly with the increase of liquid to solid (L/S) ratio or washing frequency. However, those of insoluble chlorides decrease slower. Moreover, Friedel's salt and its related compound (11CaO.7Al(2)O(3).CaCl(2)) were reliable standards for the insoluble chlorides in RFA, which are strongly related to CaCl(2). Washing of RFA promoted the release of insoluble chlorides, most of which were in the form of CaCl(2).

In situ time-resolved XAFS studies of metal particle formation by photoreduction in polymer solutions.

Formation mechanisms of metal particles (rhodium (Rh) and palladium (Pd) particles) in an aqueous ethanol solution of poly(N-vinyl-2-pyrrolidone) (PVP) by photoreduction were investigated by UV-vis, transmission electron microscopy (TEM), and in situ X-ray absorption fine structure (in situ XAFS). The average diameter of the Rh and Pd particles prepared by the photoreduction was estimated from TEM to be 2.2 and 2.0 nm, respectively. In situ energy-dispersive XAFS (in situ DXAFS) measurements were performed to investigate the reduction process of Rh(III) and Pd(II) aqua chlorocomplexes as well as their particle formation process. The reduction rate of these aqua chlorocomplexes could be quantitatively evaluated from the change of X-ray absorbance assigned to the contribution of metal-chloride bonds in these complexes. The reduction rate of Rh(III) aqua chlorocomplexes was found to be slower than that of Pd(II). It was also demonstrated that the reduction process of Rh(III) complexes possessed an induction period before the onset of Rh particle formation, although the Pd(II) complexes displayed no induction period, since the reduction of Pd(II) occurred immediately after mixing of an ethanol solution of Pd(II) complexes with aqueous PVP solutions.

In situ time-resolved XAFS analysis of silver particle formation by photoreduction in polymer solutions.

Formation mechanisms of silver (Ag) particles in an aqueous ethanol solution of poly(N-vinyl-2-pyrrolidone) (PVP) by the photoreduction of AgClO(4) were investigated by using UV-Vis, transmission electron microscopy (TEM), extended X-ray absorption fine structure (XAFS), and in situ energy-dispersive X-ray absorption fine structure (in situ DXAFS) measurements. The average diameter of the Ag particles prepared in the presence and absence of benzoin as a photo-activator was estimated from TEM to be 7.4 and 5.1 nm, respectively, and their particle size distributions ranged from 2 to 15 nm. XAFS analysis indicated that metallic Ag particles were synthesized, and the reduction rate of Ag(+) to Ag(0), the creation of Ag(0)-Ag(0) bonds and their particle growth by the association of Ag(0)-Ag(0) was regulated by the metal concentration and the inclusion of benzoin. In situ DXAFS measurements were performed in real time to investigate the kinetics of Ag(+) reduction and Ag particle formation. During the induction period the reduction of Ag(+) to Ag(0) occurred, and subsequent nucleation and growth process concurrently proceeded after the induction period. The intermediate small Ag particles (C.N. smaller than about 4) were generated in the nucleation process, and grown up to larger particles (C.N.s equal to 4.5+/-1.5) in the longer-duration photoreduction.

Water exchange dynamics of manganese(II), cobalt(II), and nickel(II) ions in aqueous solution.

The first row transition metal ions Mn(2+), Co(2+), and Ni(2+) have been studied by classical umbrella sampling molecular dynamics simulations. The water exchange mechanisms, estimates of reaction rates, as well as structural changes during the activation process are discussed. Mn(2+) was found to react via an I(A) mechanism, whereas Co(2+) and Ni(2+) both proceed via I(D). Reaction rate constants are generally higher than those obtained by experiment but the simply constructed metal(II) ion-water potential reproduces the relative order quite well.