Publishing type：Research paper (scientific journal)  

DOI： 10.1039/d0tc04307a

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Publishing type：Research paper (scientific journal)  

DOI： 10.1063/5.0033761

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Language：English   Publishing type：Research paper (scientific journal)  

Two bacterial strains isolated from soil, namely Agreia sp. D1110 and Microbacterium trichothecenolyticum D2006, were found to produce a novel oligosaccharide. The oligosaccharide was enzymatically produced from dextran using the culture supernatant of Agreia sp. D1110 or M. trichothecenolyticum D2006. LC-MS and NMR analysis identified the novel oligosaccharide as cyclo-{→6)-α-d-Glcp-(1→6)-α-d-Glcp-(1→6)-α-d-Glcp-(1→6)-α-d-Glcp-(1→}, which was named cycloisomaltotetraose, and abbreviated as CI4. CI4 was subsequently crystalized and its X-ray crystallographic structure was determined. CI4 crystals were shown to be pentahydrate, with the CI4 molecules in the crystal structure displaying a unique 3D structure, in which two glucosyl residues in the molecule were facing each other. This unique 3D structure was quite different from the 3D structure of known cyclic tetrasaccharides. This is the first report of CI4 molecules and their unique crystal structure.

DOI： 10.1016/j.carres.2020.108104

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Language：English   Publishing type：Research paper (scientific journal)  

Simple synthetic procedures for accessing novel metal-substituted tungstosulfates [SMW11O39]4- with Keggin-type structures were developed based on the reaction of metal ions (M = Mn2+, Co2+, Ni2+, and Cu2+) with lacunary tungstosulfate, [SW11O39]6-, which was obtained by treating [SW12O40]2- with a weak base in acetone. All metal-substituted tungstosulfates were characterized by elemental analysis, X-ray crystallography, ESI-MS, IR, Raman, UV-Vis and cyclic voltammetry analyses.

DOI： 10.1039/c9dt04737a

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Publishing type：Research paper (scientific journal)  

DOI： 10.1246/bcsj.20190326

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DOI： 10.1063/5.0021338

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DOI： 10.1002/ejic.201901298

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DOI： 10.7566/JPSJ.89.123701

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Language：English   Publishing type：Research paper (scientific journal)  

The temperature dependence of the resistivity (ρ) of Ag-doped Bi2Se3 (AgxBi2-xSe3) shows insulating behavior above 35 K, but below 35 K, ρ suddenly decreases with decreasing temperature, in contrast to the metallic behavior for non-doped Bi2Se3 at 1.5-300 K. This significant change in transport properties from metallic behavior clearly shows that the Ag doping of Bi2Se3 can effectively tune the Fermi level downward. The Hall effect measurement shows that carrier is still electron in AgxBi2-xSe3 and the electron density changes with temperature to reasonably explain the transport properties. Furthermore, the positive gating of AgxBi2-xSe3 provides metallic behavior that is similar to that of non-doped Bi2Se3, indicating a successful upward tuning of the Fermi level.

DOI： 10.1038/s41598-019-41906-7

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DOI： 10.7566/JPSJ.88.063704

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DOI： 10.1103/PhysRevB.100.094525

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DOI： 10.1002/ejic.201800541

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Language：English   Publishing type：Research paper (scientific journal)  

Cyclic α-maltosyl-(1→6)-maltose (CMM, cyclo-{→6)-α-d-Glcp-(1→4)-α-d-Glcp-(1→6)-α-d-Glcp-(1→4)-α-d-Glcp-(1→})is a cyclic glucotetrasaccharide with alternating α-1,4 and α-1,6 linkages. CMM is composed of two maltose units and is one of the smallest cyclic glucooligosaccharides. Although CMM is resistant to usual amylases, it is efficiently hydrolyzed by CMM hydrolase (CMMase), belonging to subfamily 20 of glycoside hydrolase family 13 (GH13_20). Here, we determined the ligand-free crystal structure of CMMase from the soil-associated bacterium Arthrobacter globiformis and its structures in complex with maltose, panose, and CMM to elucidate the structural basis of substrate recognition by CMMase. The structures disclosed that although the monomer structure consists of three domains commonly adopted by GH13 and other α-amylase-related enzymes, CMMase forms a unique wing-like dimer structure. The complex structure with CMM revealed four specific subsites, namely -3', -2, -1, and +1'. We also observed that the bound CMM molecule adopts a low-energy conformer compared with the X-ray structure of a single CMM crystal, also determined here. Comparison of the CMMase active site with those in other enzymes of the GH13_20 family revealed that three regions forming the wall of the cleft, denoted PYF (Pro-203/Tyr-204/Phe-205), CS (Cys-163/Ser-164), and Y (Tyr-168), are present only in CMMase and are involved in CMM recognition. Combinations of multiple substitutions in these regions markedly decreased the activity toward CMM, indicating that the specificity for this cyclic tetrasaccharide is supported by the entire shape of the pocket. In summary, our work uncovers the mechanistic basis for the highly specific interactions of CMMase with its substrate CMM.

DOI： 10.1074/jbc.RA118.004472

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Language：English   Publishing type：Research paper (scientific journal)  

A mono-potassium cation-encapsulated Preyssler-type phosphotungstate, [P5W30O110K]14- (1), was prepared as a potassium salt, K14[P5W30O110K] (1a), by heating mono-bismuth- or mono-calcium-encapsulated Preyssler-type phosphotungstates (K12[P5W30O110Bi(H2O)] or K13[P5W30O110Ca(H2O)]) in acetate buffer. Characterization of the potassium salt 1a by single-crystal X-ray structure analysis, 31P and 183W nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy, high-resolution electrospray ionization mass spectroscopy, and elemental analysis revealed that one potassium cation is encapsulated in the central cavity of the Preyssler-type phosphotungstate molecule with a formal D 5h symmetry. Density functional theory calculations have confirmed that the potassium cation prefers the central position of the cavity over a side position, in which no water molecules are coordinated to the encapsulated potassium cation. 31P NMR and cyclic voltammetry analyses revealed the rapid protonation-deprotonation of the oxygens in the cavity compared to that of other Preyssler-type compounds. Heating of 1a in the solid state afforded a di-K+-encapsulated compound, K13[P5W30O110K2] (2a), indicating that a potassium counter-cation is introduced in one of the side cavities, concomitantly displacing the internal potassium ion from the center to a second side cavity, thus providing a new method to encapsulate an additional cation in Preyssler compounds.

DOI： 10.1021/acsomega.8b00163

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Publishing type：Research paper (scientific journal)  

DOI： 10.1002/ejic.201701311

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DOI： 10.1016/j.tetlet.2017.12.049

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DOI： 10.1002/pssb.201800200

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DOI： 10.7566/JPSJ.87.073708

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DOI： 10.7567/JJAP.57.028001

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Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevB.97.104503

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Language：English   Publishing type：Research paper (scientific journal)  

Azulene-fused polycyclic aromatic hydrocarbons (PAHs) were synthesized from commercially available azulene in four steps. The resulting azulene conjugates exhibited significantly narrow HOMO-LUMO bandgaps with high air stability, confirmed by photophysical study. Introduction of azulene also enabled the unique reversible stimuli-responsiveness even with the weak acid and base, which can potentially control the degree of conjugation and optoelectronic properties by simple acid-base and redox processes.

DOI： 10.1021/acs.orglett.7b02729

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Among chiral macrocycles 1 synthesized, 1m with the 3,5-bis(trifluoromethyl)phenylethynyl group was the best organocatalyst for the enantioselective synthesis of cyclic carbonates from disubstituted or monosubstituted epoxides and CO2. The X-ray crystal structure of 1m revealed a well-defined chiral cavity with multiple hydrogen-bonding sites that is suitable for the enantioselective activation of epoxides. A catalytic cycle proposed was supported by DFT calculations.

DOI： 10.1021/acs.orglett.7b01838

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Here, we report a simple and direct method to visualize the protonation/deprotonation of an amine active pharmaceutical ingredient (API) in the solid state using a solid-vapor reaction with propargyl bromide and Raman imaging for the assessment of the API during the manufacturing process of solid formulations. An alkyne tagging occurred on the free form of solid haloperidol by the vapor phase reaction, and a distinct Raman signal of alkyne was detected. Alkyne signal monitoring by Raman imaging enabled us to visualize the distribution of the free-form haloperidol in a solid formulation. On the other hand, haloperidol hydrochloride did not react with propargyl bromide in the solid-vapor reaction, and the alkyne signal was not observed. Using the difference in reactivity, the protonation/deprotonation of the amine API in the solid state could be visualized. As an example of application, we tried to visually assess the protonation/deprotonation state when the free-form haloperidol was ground with acids using the solid-vapor reaction and Raman imaging and found that haloperidol was partially protonated when ground with 2 equivalents of hydrogen chloride. Furthermore, we demonstrated the relationship between the degree of protonation and the amount of water added as a medium for grinding haloperidol with succinic acid.

DOI： 10.1016/j.xphs.2017.03.006

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The structure of the Keggin-type β-[PW12O40]3- (PW12) polyoxometalate, with n-Bu4N+ as the countercation, has been determined for the first time by single-crystal X-ray analysis and compared to data obtained from a new determination of the structure of the α-PW12 isomer, having the same countercation. Analysis of cyclic voltammograms obtained in CH3CN (0.1 M [n-Bu4N][PF6]) reveals that the reversible potential for the β-PW12 isomer always remains ca. 100 mV more positive than that of the α-PW12 isomer on addition of the acid CF3SO3H. Simulations of the cyclic voltammetry as a function of acid concentration over the range 0-5 mM mimic experimental data exceptionally well. These simulation-experiment comparisons provide access to reversible potentials and acidity constants associated with α and β fully oxidized and one- and two-electron reduced systems and also explain how the two well-resolved one-electron W(VI)/W(V) processes converge into a single two-electron process if sufficient acid is present. 183W NMR spectra of the oxidized forms of the PW12 isomers are acid dependent and in the case of β-PW12 imply that the bridging oxygens between the WI and WII units are preferentially protonated in acidic media. EPR data on frozen solutions of one-electron reduced β-[PWVWVI11O40]4- indicate that either the WI or the WIII unit in β-PW12 is reduced in the β-[PWVI12O40]3-/β-[PWVWVI11O40]4- process. In the absence of acid, reversible potentials obtained from the α- and β-isomers of PW12 and [SiW12O40]4- exhibit a linear relationship with solvent properties such as Lewis acidity, acceptor number, and polarity index.

DOI： 10.1021/acs.inorgchem.6b03046

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DOI： 10.1002/poc.3726

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DOI： 10.7566/JPSJ.86.025002

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DOI： 10.1103/PhysRevB.95.245310

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DOI： 10.3987/COM-17-13820

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Language：English   Publishing type：Research paper (scientific journal)  

Dipotassium cation (K+)-encapsulated Preyssler-type phosphotungstate, [P5W30O110K2]13-, was prepared by heating monobismuth (Bi3+)-encapsulated Preyssler-type phosphotungstate, [P5W30O110Bi(H2O)]12-, in acetate buffer in the presence of an excess amount of potassium cations. Characterization of the isolated potassium salt, K13[P5W30O110K2] (1a), and its acid form, H13[P5W30O110K2] (1b), by single crystal X-ray structure analysis, 31P and 183W nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR) spectroscopy, cyclic voltammetry (CV), high-resolution electrospray ionization mass spectroscopy (HR-ESI-MS), and elemental analysis revealed that two potassium cations are encapsulated in the Preyssler-type phosphotungstate molecule with formal D5h symmetry, which is the first example of a Preyssler-type compound with two encapsulated cations. Incorporation of two potassium cations enhances the thermal stability of the potassium salt, and the acid form shows catalytic activity for hydration of ethyl acetate. Packing of the Preyssler-type molecules was observed by high-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM).

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Language：English   Publishing type：Research paper (scientific journal)  

We report syntheses of new superconducting metal-doped MoSe2 materials (MxMoSe2). The superconducting MxMoSe2 samples were prepared using a liquid NH3 technique, and can be represented as '(NH3)yMxMoSe2'. The Tcs of these materials were approximately 5.0 K, independent of x and the specific metal atom. X-ray diffraction patterns of (NH3)yNaxMoSe2 were recorded using polycrystalline powders. An increase in lattice constant c showed that the Na atom was intercalated between MoSe2 layers. The x-independence of c was observed in (NH3)yNaxMoSe2, indicating the formation of a stoichiometric compound in the entire x range, which is consistent with the x-independence of Tc. A metallic edge of the Fermi level was observed in the photoemission spectrum at 30 K, demonstrating its metallic character in the normal state. Doping of MoSe2 with Li and K also yielded superconductivity. Thus, MoSe2 is a promising material for designing new superconductors, as are other transition metal dichalcogenides.

DOI： 10.1038/srep29292

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DOI： 10.1016/j.ica.2016.01.023

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DOI： 10.1063/1.4972400

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DOI： 10.1055/s-0035-1562470

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Language：English   Publishing type：Research paper (scientific journal)  

Mechanochromic organic molecules (MOMs) that exhibit a large difference of fluorescence wavelength between two states have important potential applications, but few such compounds are known. Here, we report a new MOM, cis-ABPX01(0), which shows switchable near-IR and blue fluorescence responses. Detailed spectrophotometric and single-crystal X-ray analyses revealed that the near-IR fluorescence is attributable to fluorescence from slip-stacked dimeric structures in crystals, while the blue fluorescence is attributable to fluorescence from the monomer. Switching between the two is achieved by dynamic structural interconversion between the two molecular packing arrangements in response to mechanical grinding and solvent vapor-fuming.

DOI： 10.1021/jacs.5b00877

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In the thyminate(2-)-bridged tetranuclear Cp*Rh(III) complexes incorporating a Na(+), Ca(2+) or Ln(3+) cation, homochiral aggregation of four Rh(III) centres was achieved to form metallacalix[4]arene-type clusters. The thyminate(2-) bridged two Rh(III) and the third metal ion with a μ3-1κN(1):2κ(2)N(3),O(2):3κO(2) mode in the Na(+) and Ca(2+) complexes, while in the Ln(3+) analogues it exhibited a different bridging mode, μ3-1κN(1):2κ(2)N(3),O(4):3κO(2).

DOI： 10.1039/c4cc09087j

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Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevB.91.174514

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DOI： 10.1002/ejic.201500226

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DOI： 10.7566/JPSJ.83.093705

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Language：English   Publishing type：Research paper (scientific journal)  

Two heterotrinuclear complexes, [Mn(II)(Ni(II)L)2].2CH3OH (where H3L = 1,1,1-tris(N-salicylideneaminomethyl)ethane) and [Fe(III)(Ni(II)L)2]NO3.C2H5OH, consisting of three face-sharing octahedra have been prepared; although these complexes have closely related structures and have the same 1-5/2-1 spin system, they show completely different magnetic interactions between the adjacent metal ions: ferromagnetic (Ni(II)-Mn(II)) and antiferromagnetic (Ni(II)-Fe(III)).

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The [Fe(II)(H(3)L)](BF(4))(2).3H(2)O (1) complex was synthesized, where H(3)L (tris[[2-[(imidazole-4-yl)methylidene]amino]ethyl]amine) is a tripodal ligand obtained by condensation of tris(2-aminoethyl)amine and 4-formylimidazole (fim) in a 1:3 molar ratio. Starting from 1, a series of complexes, [Fe(II)(H(1.5)L)](BF(4))(0.5) (2) (=[Fe(II)(H(3)L)][Fe(II)(L)]BF(4)), [Fe(H(1.5)L)]BF(4) (3) (=[Fe(II)(H(3)L)][Fe(III)(L)](BF(4))(2)), [Fe(III)(H(3)L)](BF(4))(3).fim.H(2)O (4), and [Fe(III)(L)].2.5H(2)O (5), has been synthesized and characterized. The single-crystal X-ray structure of each complex has been determined. The Fe(II) compound, 2, and a mixed valence Fe(II)-Fe(III) compound, 3, involve formally hemi-deprotonated ligands, H(1.5)L. The structure of 3 consists of a homochiral two-dimensional assembled sheet, arising from the intermolecular hydrogen bonds between [Fe(II)(H(3)L)](2+) and [Fe(III)(L)](0) (3). All but 5 exhibit spin crossover between low-spin (LS) and high-spin (HS) states. This is a rare case where both Fe(II) and Fe(III) complexes containing the same ligand exhibit spin-crossover behavior. Magnetic susceptibility and Mössbauer studies showed that 3 has three accessible electronic states: LS Fe(II)-LS Fe(III), HS Fe(II)-LS Fe(III), and HS Fe(II)-HS Fe(III). Compounds 1-3 show the light-induced excited spin-state trapping effect at the Fe(II) sites upon irradiation with green light. The solution magnetic properties, electronic spectra, and electrochemical properties of 1, 4, and 5 were also studied.

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DOI： 10.1107/S0108767304098794

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Language：English   Publishing type：Research paper (scientific journal)  

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