Accurate calculation of core-electron binding energies: multireference perturbation treatment

Multireference perturbation theory (MRPT) with multiconfigurational self-consistent field (MCSCF) reference functions is applied to the calculations of core-electron binding energies (CEBEs) of atoms and molecules. Orbital relaxations in a core-ionized state and electron correlation are both taken into account in a conventional MCSCF-MRPT procedure. In the MCSCF calculation, the target core ionized state is directly optimized as an excited state and this treatment can completely prevent a variational collapse. Multireference Moller-Plesset perturbation theory and multiconfigurational self-consistent field reference quasidegenerated perturbation theory were used to treat electron correlation. The present method quite accurately reproduced the 1s CEBEs of CH4, NH3, H2O, and FH; the average deviation from the experimental data is 0.11 eV using Ahlrichs' VTZ basis set. The C 1s and O 1s CEBEs of formic acid and acetic acid were calculated and the results are consistent with the bonding characters of the atoms in these molecules. The present procedure can also be applied to CEBEs of higher angular momentum orbitals by including spin-orbit coupling. The calculated CEBEs of Ar 2p, HCl 2p, Kr 3d, and HBr 3d are in reasonable agreement with the available experimental values. In the calculation of the 3d CEBEs, a relativistic correction significantly improves the agreements. The effect of polarization functions is also discussed.     

Adduct of acetylene at sulfur in an oxygen- and sulfur-bridged open cubane cluster complex of tungsten

Formation of a single carbon-sulfur bond is described. The reaction of incomplete cubane-type sulfur and oxygen-bridged isothiocyanato tungsten cluster [W3(mu3-S)(mu-O)(mu-S)2(NCS)9]5- (7) with acetylene affords [W3(mu3-S)(mu-O)(mu-S)(mu-SCH=CH2)(NCS)9]4- (8). The cluster 8 has been isolated as K0.5(Hpy)3.5[W3(mu3-S)(mu-O)(mu-S)(mu-SCH=CH2)(NCS)9] (8'), whose structure has been characterized by X-ray crystallography, electronic spectra, and 1H and 13C NMR spectroscopy. Crystal data of 8': triclinic system, space group P1, a = 14.465(5) A, b = 17.353(3) A, c = 10.202(2) A, alpha = 90.98(1) degrees, beta = 108.59(2) degrees, gamma = 98.13(2) degrees, V = 2397.6(10) A(3), Z = 2, D(c) = 2.096 g cm(-3), Dm = 2.08 g cm(-3), R (Rw) = 3.6 (5.5)% for 8786 reflections (I > 1.50 sigma(I)). The carbon-carbon distance is 1.27(1) A and is almost equidistant between ethylene (1.339 A) and acetylene (1.203 A). The electronic spectrum of 8' in 1.0 M HCl containing 1.5 M KSCN has a characteristic broad peak in the near-infrared region [lambda(max), nm (epsilon, M(-1) cm(-1)): 840 (650), 575 (1450)]. (1)H NMR and HH correlation spectroscopy (COSY) of 8' in CD3CN support the results of the X-ray structural analysis. The (1)H NMR spectrum shows three signals at 2.42 (1H, dd), 4.84 (1H, d, J = 8.8 Hz), and 4.89 (1H, d, J = 16.2 Hz) ppm due to the mu-SCH=CH2 moiety of 8'. The correlation spectrum shows spin couplings of the signal at 2.42 ppm with the signals at 4.84 and 4.89 ppm. The mechanism of the formation of 8 is suggested to proceed through an intermediate with acetylene bridging two of the sulfur atoms.     

Application of integrated SECM ultra-micro-electrode and AFM force probe to biosensor surfaces

The integration of scanning electrochemical ultra-micro-electrode (UME) with atomic force microscope cantilever probe have been achieved by using a homemade photolithography system. A gold-film-coated AFM cantilever was insulated with photo resist coating and a pointed end of the AFM probe was opened by illuminating with maskless arbitrary optical micro-pattern generator. To realize precise control of probe sample distance constantly, the resulting scanning electrochemical microscopy (SECM)-AFM probe was operated using a dynamic force microscopy (DFM) technique with magnetic field excitation. From a steady-state voltammetric experiment, the effective electrode diameters of the probes thus prepared were estimated to be from 0.050 to 6.2 microm. The capability of this SECM-AFM probe have been tested using gold comb in the presence of Fe(CN)(6)(3-). The simultaneous imaging of the topography and electrochemical activity of the strip electrode was successfully obtained. We also used the SECM-AFM to examine in situ topography and enzymatic activity measurement. Comparison of topography and oxidation current profiles above enzyme-modified electrode showed active parts distribution of biosensor surface.     

Solid state synthesis and crystal structure of a novel cluster, [WS4Ag3I(AsPh3)3](SAsPh3)

Summary The cluster [WS₄Ag₃I(AsPh₃)₃](SAsPh₃) was prepared by the solid state reaction of (NH₄)₂WS₄, AgI and AsPh₃ at low heat. Some As^III atoms were oxidized to As^v in the process. The structure of [WS₄Ag₃I(AsPh₃)₃](SAsPh₃) was determined by single crystal X-ray diffractometry and can be described as the combination of cubane-like [WS₄Ag₃I(AsPh₃)₃] with an SAsPh₃ moiety.     

Intramolecular exciplex laser

Laser action of the intramolecular exciplex emission of p-(9′-anthryl)-N,N-dimethylaniline (ADMA) has been found in non-polar and slightly polar solvents. In moderately as well as strongly polar solvents, the laser emission is quenched in spite of the fact that the spontaneous fluorescence yields is larger in polar than in non-polar solvents.     

Water-Tolerant Superbase Polyoxometalate [H2(Nb6O19)]6− for Homogeneous Catalysis

Here, doubly protonated Lindqvist-type niobium oxide cluster [H₂(Nb₆O₁₉)]^6–, fabricated by microwave-assisted hydrothermal synthesis, exhibited superbase catalysis for Knoevenagel and crossed aldol condensation reactions accompanied by activating C−H bond with pK_a >26 and proton abstraction from a base indicator with pK_a=26.5. Surprisingly, [H₂(Nb₆O₁₉)]⁶⁻ exhibited water-tolerant superbase properties for Knoevenagel and crossed aldol condensation reactions in the presence of water, although it is well known that the strong basicity of metal oxides and organic superbase is typically lost by the adsorption of water. Density functional theory calculation revealed that the basic surface oxygens that share the corner of NbO₆ units in [H₂(Nb₆O₁₉)]⁸⁻ maintained the negative charges even after proton adsorption. This proton capacity and the presence of un-protonated basic sites led to the water tolerance of the superbase catalysis.     

Variable control of the electronic states of a silver nanocluster via protonation/deprotonation of polyoxometalate ligands

The properties of metal nanoclusters depend on both their structures and electronic states. However, in contrast to the significant advances achieved in the synthesis of structurally well-defined metal nanoclusters, systematic control of their electronic states is still challenging. In particular, stimuli-responsive and reversible control of the electronic states of metal nanoclusters is attractive from the viewpoint of their practical applications. Recently, we developed a synthesis method for atomically precise Ag nanoclusters using polyoxometalates (POMs) as inorganic ligands. Herein, we exploited the acid/base nature of POMs to reversibly change the electronic states of an atomically precise {Ag₂₇} nanocluster via protonation/deprotonation of the surrounding POM ligands. We succeeded in systematically controlling the electronic states of the {Ag₂₇} nanocluster by adding an acid or a base (0–6 equivalents), which was accompanied by drastic changes in the ultraviolet-visible absorption spectra of the nanocluster solutions. These results demonstrate the great potential of Ag nanoclusters for unprecedented applications in various fields such as sensing, biolabeling, electronics, and catalysis.

The electronic states of Ag nanoclusters were reversibly controlled driven by protonation/deprotonation of polyoxometalate ligands.     

Determination of trace impurities in high-purity iron using salting-out of polyoxyethylene-type surfactants

To an iron sample solution was added polyoxyethylene-4-isononylphenoxy ether (PONPE, nonionic surfactant, average number of ethylene oxides 7.5) and the surfactant was aggregated by the addition of lithium chloride. The iron(III) matrix was collected into the condensed surfactant phase in >99.9% yields, leaving trace metals [e.g., Ti(IV), Cr(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Pb(II), and Bi(III)] in the aqueous phase. After removing the surfactant phase by centrifugation, the remaining trace metals were concentrated onto an iminodiacetic acid-type chelating resin. The trace metals were desorbed with dilute nitric acid for the determination by inductively coupled plasma-mass spectrometry or graphite-furnace atomic absorption spectrometry. The proposed separation method allowed the analysis of high-purity iron metals for trace impurities at low μg g⁻¹ to ng g⁻¹ levels.     

(<Emphasis Type="Italic">q</Emphasis>,<Emphasis Type="Italic">t</Emphasis>)-Deformations of multivariate hook product formulae

We generalize multivariate hook product formulae for P-partitions. We use Macdonald symmetric functions to prove a (q,t)-deformation of Gansner’s hook product formula for the generating functions of reverse (shifted) plane partitions. (The unshifted case has also been proved by Adachi.) For a d-complete poset, we present a conjectural (q,t)-deformation of Peterson–Proctor’s hook product formula.     

Distinguishing hepatic hemangiomas from metastatic tumors using T1 mapping on gadoxetic-acid-enhanced MRI

Objective

The objective was to evaluate the usefulness of T1 mapping in distinguishing hepatic hemangiomas from metastatic tumors on gadoxetic-acid-enhanced magnetic resonance imaging.

Methods

We examined 20 hemangiomas in 14 patients and 21 metastatic tumors in 11 patients. We performed T1 mapping using the double-flip angle method before and after the injection of gadoxetic acid. Quantitative evaluation was carried out using the pre- and post-contrast enhancement ratios (CERs), and qualitative evaluation was conducted to evaluate the added value of T1 mapping using receiver operating characteristics analysis.

Results

The mean CERs of metastatic tumors at 70 s, 240 s and 20 min after the injection of gadoxetic acid were 1.54 (95% confidence interval: 1.37–1.71), 1.47 (1.34–1.6) and 1.30 (1.19–1.41); those of hemangiomas were 3.36 (2.41–4.31), 3.06 (2.44–3.68) and 2.20 (2.02–2.38), respectively. The mean CERs of hemangiomas were significantly higher than those of metastatic tumors (P< .05). When the mean CER cutoff value 20 min after the injection was set at 1.6, the diagnostic sensitivity of hepatic hemangiomas was 100%. There was no added value observed statistically in the qualitative evaluation of T1 mapping (P> .05).

Conclusion

It is valuable to evaluate quantitatively T1 mapping 20 min after hepatobiliary phase acquisition in the case of difficulty in distinguishing hepatic hemangiomas from metastatic tumors qualitatively.