24 research outputs found

    好アルカリ性Bacillus A-007株のK^+ : 促進ATPaseについて

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    1.好アルカリ性Bacillus A-007株の生育にとってK^+は必須であった.2.K^+-濃度を制限した培地(1.5mMK^+)で生育させた細胞の膜画分に, K^+により促進されるATPase活性が認められた.3.K^+促進ATPaseは, 動力学的特性及びウワバイン, NaN_3, PCMBに対する感受件において, 同菌株のH^+-ATPaseと明らかに異なっていた.1. K^+ was essential for the growth of an alkalophilic Bacillus A-007. 2. Membrane fraction, which was prepared from the cells grown in K^+ -limited medium (1.5mM K^+), showed K^+ -stimulated ATPase activity. 3. The K^+ -stimulated ATPase was clearly different from H^+ -ATPase on kinetical profile and ouabain-, NaN_3- and PCMB-sensvtivity

    Self-Assembly of Pentanuclear Mesocate versus Octanuclear Helicate: Size Effect of the [M<sup>II</sup><sub>3</sub>(μ<sub>3</sub>‑O/X)]<sup><i>n</i>+</sup> Triangle Core

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    The first cluster mesocate (H<sub>3</sub>O)­[{Fe<sub>2</sub>(μ-L)<sub>3</sub>}­{Fe<sub>3</sub>(μ<sub>3</sub>-O)­(μ-Cl)<sub>3</sub>}]·3EtOH (<b>1</b>) and a new series of cluster helicates, [{Mn­(μ-L)<sub>3</sub>}<sub>2</sub>{Mn<sub>3</sub>(μ<sub>3</sub>-Cl)}<sub>2</sub>]­(ClO<sub>4</sub>)<sub>2</sub>·2MeOH·6H<sub>2</sub>O (<b>2</b>), [{Cd­(μ-L)<sub>3</sub>}<sub>2</sub>{Cd<sub>3</sub>(μ<sub>3</sub>-Br)}<sub>2</sub>]­Br<sub>2</sub>·2DMF·14H<sub>2</sub>O (<b>3</b>), and [{Cd­(μ-L)<sub>3</sub>}<sub>2</sub>{Cd<sub>3</sub>(μ<sub>3</sub>-I)}<sub>2</sub>]­(CdI<sub>4</sub>)·3H<sub>2</sub>O (<b>4</b>), have been synthesized by the self-assembly of a <i>C</i><sub>2</sub>-symmetric tritopic ligand, 2,6-bis­[5-(2-pyridinyl)-1<i>H</i>-triazol-3-yl]­pyridine (H<sub>2</sub>L) with different metal halogen salts. Single-crystal X-ray diffraction and electrospray ionization mass spectrometry measurements were carried out on these complexes. <b>1</b> was crystallized as a triple-stranded pentanuclear mesocate in which a [Fe<sup>II</sup><sub>3</sub>(μ<sub>3</sub>-O)]<sup>4+</sup> triangle core was wrapped by a [Fe<sup>II</sup><sub>2</sub>(μ-L)<sub>3</sub>]<sup>2–</sup> shell. <b>2</b>–<b>4</b> have similar octanuclear helicate structures in which two propeller-shaped [M<sup>II</sup>(μ-L)<sub>3</sub>]<sup>4–</sup> units embrace two [M<sup>II</sup><sub>3</sub>(μ<sub>3</sub>-X)]<sup>5+</sup> triangles inside. The [M<sup>II</sup><sub>3</sub>(μ<sub>3</sub>-O/X)]<sup><i>n</i>+</sup> triangle core were found to play an important role in the selective synthesis of the two architectures: the smaller [Fe<sup>II</sup><sub>3</sub>(μ<sub>3</sub>-O)]<sup>4+</sup> triangle core prefers a mesocate structure because it matches the small cavity imposed by the [Fe<sup>II</sup><sub>2</sub>(μ-L)<sub>3</sub>]<sup>2–</sup> shell, while the bigger [M<sup>II</sup><sub>3</sub>(μ<sub>3</sub>-X)]<sup>5+</sup> induces a screwed arrangement of the ligands, thus stabilizing the helicate structure. Variable-temperature magnetic susceptibility measurements indicate that both <b>1</b> and <b>2</b> display an overall antiferromagnetic coupling. Density functional theory calculations for <b>1</b> confirm the strong antiferromagnetic interaction in the central [Fe<sup>II</sup><sub>3</sub>(μ<sub>3</sub>-O)]<sup>4+</sup>, while interaction through the triazole bridging ligands is slightly ferromagnetic. For <b>2</b>, three interaction pathways were considered and all sets of <i>J</i> values reveal the presence of weak antiferromagnetic interaction

    Disklike Hepta- and Tridecanuclear Cobalt Clusters. Synthesis, Structures, Magnetic Properties, and DFT Calculations

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    The synthesis, structure and magnetic properties are reported of two disklike mixed-valence cobalt clusters [Co<sup>III</sup>Co<sup>II</sup><sub>6</sub>(thmp)<sub>2</sub>­(acac)<sub>6</sub>(ada)<sub>3</sub>] (<b>1</b>) and [Co<sup>III</sup><sub>2</sub>Co<sup>II</sup><sub>11</sub>­(thmp)<sub>4</sub>(Me<sub>3</sub>CCOO)<sub>4</sub>­(acac)<sub>6</sub>(OH)<sub>4</sub>­(H<sub>2</sub>O)<sub>4</sub>]­(Me<sub>3</sub>CCOO)<sub>2</sub>·H<sub>2</sub>O (<b>2</b>). Heptanuclear complex <b>1</b> was prepared by solvothermal reaction of cobalt­(II) acetylacetonate (Co­(acac)<sub>2</sub>), 1,1,1-tris­(hydroxymethyl)-propane (H<sub>3</sub>thmp), and adamantane-1-carboxylic acid (Hada), whereas by substituting Hada with Me<sub>3</sub>CCO<sub>2</sub>H, tridecanuclear complex <b>2</b> was obtained with an unexpected [Co<sup>III</sup><sub>2</sub>Co<sup>II</sup><sub>11</sub>] core. The core structures of <b>1</b> and <b>2</b> are related to each other: that of <b>1</b> arranges as a centered hexagon of a central Co<sup>III</sup> ion surrounded by a [Co<sup>II</sup><sub>6</sub>] hexagon, while that of <b>2</b> can be described as a larger oligomer based on two vertex-sharing [Co<sup>III</sup>Co<sup>II</sup><sub>6</sub>] clusters. Variable-temperature direct-current magnetic susceptibility measurements demonstrated overall ferromagnetic coupling between the Co<sup>II</sup> ions within both clusters. The magnetic exchange (<i>J</i>) and magnetic anisotropy (<i>D</i>) values were quantified with appropriate spin-Hamiltonian models and were also supported by density functional theory calculations. The presence of frequency-dependent out-of-phase (χ<sub>M</sub><i>″</i>) alternating current susceptibility signals at temperatures below 3 K suggested that <b>2</b> might be a single-molecule magnet

    Polynuclear and Polymeric Gadolinium Acetate Derivatives with Large Magnetocaloric Effect

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    Two ferromagnetic μ-oxo<sub>acetate</sub>-bridged gadolinium complexes [Gd<sub>2</sub>(OAc)<sub>2</sub>(Ph<sub>2</sub>acac)<sub>4</sub>(MeOH)<sub>2</sub>] (<b>1</b>) and [Gd<sub>4</sub>(OAc)<sub>4</sub>(acac)<sub>8</sub>(H<sub>2</sub>O)<sub>4</sub>] (<b>2</b>) and two polymeric Gd­(III) chains [Gd­(OAc)<sub>3</sub>(MeOH)]<sub><i>n</i></sub> (<b>3</b>) and [Gd­(OAc)<sub>3</sub>(H<sub>2</sub>O)<sub>0.5</sub>]<sub><i>n</i></sub> (<b>4</b>) (Ph<sub>2</sub>acacH = dibenzoylmethane; acacH = acetylacetone) are reported. The magnetic studies reveal that the tiny difference in the Gd–O–Gd angles (Gd···Gd distances) in these complexes cause different magnetic coupling. There exist ferromagnetic interactions in <b>1</b>–<b>3</b> due to the presence of the larger Gd–O–Gd angles (Gd···Gd distances), and antiferromagnetic interaction in <b>4</b> when the Gd–O–Gd angle is smaller. Four gadolinium acetate derivatives display large magnetocaloric effect (MCE). The higher magnetic density or the lower <i>M</i><sub>W</sub>/<i>N</i><sub>Gd</sub> ratio they have, the larger MCE they display. Complex <b>4</b> has the highest magnetic density and exhibits the largest MCE (47.7 J K<sup>–1</sup> kg<sup>–1</sup>). In addition, complex <b>3</b> has wider temperature and/or field scope of application in refrigeration due to the dominant ferromagnetic coupling. Moreover, the statistical thermodynamics on entropy was successfully applied to simulate the MCE values. The results are quite in agreement with those obtained from experimental data

    Planar Cu<sub>2</sub>(ppz)<sub>2</sub> Dimers as SBUs for Diverse Polyoxometalate-Based Metal Organic Frameworks

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    Five new polyoxometalate-based metal organic frameworks, [Cu<sub>4</sub>(ppz)<sub>4</sub>(PO<sub>4</sub>)]·​[CuBr<sub>2</sub>] (<b>1</b>), [Cu<sub>4</sub>(ppz)<sub>4</sub>­(MoO<sub>4</sub>)<sub>2</sub>­(H<sub>2</sub>O)]·​2H<sub>2</sub>O (<b>2</b>), [Cu­(Hppz)­(Mo<sub>2</sub>O<sub>7</sub>)] (<b>3</b>), [Cu<sub>2</sub>(ppz)<sub>2</sub>­(Mo<sub>3</sub>O<sub>10</sub>)] (<b>4</b>), and [Cu<sub>6</sub>(ppz)<sub>6</sub>­(PMo<sub>3</sub><sup>V</sup>Mo<sub>9</sub><sup>VI</sup>O<sub>40</sub>)] (<b>5</b>) (Hppz = 2-(1<i>H</i>-pyrazol-3-yl)­pyrazine), have been hydrothermally synthesized and fully characterized, in which a planar Cu<sub>2</sub>(ppz)<sub>2</sub> dimer acts as a secondary building unit (SBU) and provides up to six potential binding sites. In virtue of the strong Jahn–Teller (JT) effect of Cu­(II) ions, the potential binding sites in the Cu<sub>2</sub>(ppz)<sub>2</sub> SBU can facilely be occupied by auxiliary oxygen-donor anions and/or outward pyrazine nitrogen atoms of neighboring SBUs. The auxiliary oxygen-donor anions in compounds <b>1</b>–<b>5</b> range from simple phosphate and molybdate, zonal Mo<sub>2</sub>O<sub>7</sub><sup>2–</sup> and Mo<sub>3</sub>O<sub>10</sub><sup>2–</sup> to a spherical three-electron reduced Keggin anion [PMo<sub>12</sub>O<sub>40</sub>]<sup>6–</sup>, respectively. Compound <b>1</b> contains an unprecedented 3D (4,6)-connected cationic open framework [Cu<sub>4</sub>(ppz)<sub>4</sub>­(PO<sub>4</sub>)]<sup>+</sup> with 1D channels filled by linear CuBr<sub>2</sub><sup>–</sup> anions, where the Cu<sub>2</sub>(ppz)<sub>2</sub> SBUs and PO<sub>4</sub> groups act as nodes and the outward Cu–N bonds and oxo bridges act as linkers. <b>2</b> possesses a complicated trinodal (3,4)-connected topological framework, in which μ<sub>3</sub>-MoO<sub>4</sub> and Cu<sub>2</sub>(ppz)<sub>2</sub> groups act as 3- and 4-connected nodes and the outward Cu–N bonds and double μ<sub>2</sub>-MoO<sub>4</sub> groups act as linkers. Differing from <b>1</b> and <b>2</b>, compound <b>3</b> shows a 2D organic–inorganic hybrid sheet constructed by a [Mo<sub>2</sub>O<sub>7</sub>]<sup>2–</sup> ribbon of cyclic hexameric edge-shared [MoO<sub>6</sub>]-octahedra and Cu<sub>2</sub>(ppz)<sub>2</sub> SBUs. Similar to <b>3</b>, compound <b>4</b> also shows 2D organic–inorganic hybrid sheets constructed by zigzag [Mo<sub>3</sub>O<sub>10</sub>]<sup>2–</sup> ribbons and Cu<sub>2</sub>(ppz)<sub>2</sub> SBUs, and adjacent sheets are extended by weak Mo–N bonds into the 3D network. <b>5</b> has a 3D 6-connected <b>pcu</b> topological framework constructed by Cu<sub>2</sub>(ppz)<sub>2</sub> SBUs and [PMo<sub>12</sub>O<sub>40</sub>]<sup>6–</sup> anions, which also can be viewed as cationic of the NbO topological [Cu<sub>6</sub>(ppz)<sub>6</sub>]<sup>6+</sup> network with cavities filled by [PMo<sub>12</sub>O<sub>40</sub>]<sup>6–</sup> anions. Magnetic measurements show that there is strong antiferromagnetic coupling within the Cu<sub>2</sub>(ppz)<sub>2</sub> dimer and only one unpaired electron within the three-electron reduced Keggin anion

    Programmed Self-Assembly of Heterometallic [3 × 3] Grid [M<sup>II</sup>Cu<sup>II</sup><sub>4</sub>Cu<sup>I</sup><sub>4</sub>] (M = Fe, Ni, Cu, and Zn)

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    A series of heterometallic [3 × 3] grids have been synthesized readily through a one-pot solvothermal reaction. Given metal ions carrying distinct electronic, magnetic, and optical information can be addressed precisely at specific locations in the array

    Exploring the Inverse Magnetocaloric Effect in Discrete Mn<sup>II</sup> Dimers

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    The inverse magnetocaloric effect (IMCE) in molecular solids is explored for two antiferromagnetically coupled Mn<sup>II</sup> dinuclear complexes. Magnetic studies reveal that both of them demonstrate the IMCE with negative magnetic entropy changes (−Δ<i>S</i><sub>M</sub> = −3.5 J kg<sup>–1</sup> K<sup>–1</sup>), which are in line with an analytic function derived from the quantized phenomenological model proposed in this work

    Mentha angustifolia

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    A family of high-nuclearity [Ln<sup>III</sup><sub>6</sub>Mn<sup>III</sup><sub>12</sub>] (Ln = Gd, Tb) nanomagnets has been synthesized, of which two are in <i>D</i><sub>2</sub> molecular symmetry and the other two are in <i>C</i><sub>1</sub> symmetry. X-ray crystallography shows that each of them contains a similar {Mn<sup>III</sup><sub>8</sub>O<sub>13</sub>} unit, four marginal Mn<sup>III</sup> ions, and two linear {Ln<sup>III</sup><sub>3</sub>} units with parallel or perpendicular orientation for high- and low-symmetry cores, respectively. For [Gd<sup>III</sup><sub>6</sub>Mn<sup>III</sup><sub>12</sub>], the distinct spins of the {Mn<sup>III</sup><sub>8</sub>O<sub>13</sub>} unit lead to different spin ground states (<i>S</i><sub>T</sub> = 23 for the high-symmetry one and <i>S</i><sub>T</sub> = 16 for the low-symmetry one), and significant magnetocaloric effects are observed in a wide temperature range [full width at half-maximum (FWHM) of −Δ<i>S</i><sub>m</sub> > 18 K] that can maximizes the refrigerant capacity, which may be attributed to the ferromagnetic interactions. By replacement of isotropic Gd<sup>III</sup> with anisotropic Tb<sup>III</sup>, they behave as single-molecule magnets, with the high-symmetry one possessing a larger effective barrier (36.6 K) than the low-symmetry one (19.6 K)

    pH-Controlled Assembly of Organophosphonate-Bridged Dysprosium(III) Single-Molecule Magnets Based on Polyoxometalates

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    Two structurally intriguing dysprosium­(III)-substituted polyoxometalates, [Dy<sub>6</sub>(ampH)<sub>4</sub>(H<sub>2</sub>O)<sub>23</sub>(ampH<sub>2</sub>)­(PW<sub>11</sub>O<sub>39</sub>)<sub>2</sub>] (<b>1</b>) and [Dy<sub>9</sub>(CO<sub>3</sub>)<sub>3</sub>(ampH)<sub>2</sub>(H<sub>2</sub>O)<sub>12</sub>(PW<sub>10</sub>O<sub>37</sub>)<sub>6</sub>]<sup>35–</sup> (<b>2</b>), are assembled by the same precursor under different pH conditions. The structure of <b>1</b> contains an octahedral {Dy<sub>6</sub>(ampH)<sub>4</sub>} core, and a unique windmill-type {Dy<sub>9</sub>(CO<sub>3</sub>)<sub>3</sub>(ampH)<sub>2</sub>} for <b>2</b>. Single-molecule magnet behavior is observed for <b>2</b> with a thermally activated energy barrier of 56 K and no appreciable quantum tunneling of magnetization under zero field

    Incomplete Spin Crossover versus Antiferromagnetic Behavior Exhibited in Three-Dimensional Porous Fe(II)-Bis(tetrazolate) Frameworks

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    Two three-dimensional (3D) Fe­(II) porous metal–organic frameworks (MOFs) [Fe<sub>2</sub>(H<sub>0.67</sub>bdt)<sub>3</sub>]·13H<sub>2</sub>O (<b>1</b>·13H<sub>2</sub>O) and [Fe<sub>3</sub>(ox)­(H<sub>0.67</sub>bdt)<sub>3</sub>(H<sub>2</sub>O)<sub>2</sub>]·solvent (<b>2</b>·solvent) (H<sub>2</sub>bdt = 5,5′-(1,4-phenylene)­bis­(1H-tetrazole); H<sub>2</sub>ox = oxalic acid; solvent = 10H<sub>2</sub>O and 9CH<sub>3</sub>OH for <b>2</b>·9MeOH and 6H<sub>2</sub>O and 5C<sub>4</sub>H<sub>9</sub>OH for <b>2</b>·5<i>n</i>-BuOH) were solvothermally synthesized and characterized. The X-ray structure analysis reveals that complex <b>1</b>·13H<sub>2</sub>O is constructed from one-dimensional (1D) {Fe­(tz)<sub>3</sub>}<sub><i>n</i></sub> (tz = tetrazolate) chains which are linked through the phenyl tethers of the bdt ligands into a 3D microporous framework. In the case of complex <b>2</b>·solvent, the linear trinuclear [Fe<sub>3</sub>(tz)<sub>6</sub>] units are linked by ox<sup>2–</sup> bridges to form 1D {Fe<sub>3</sub>(tz)<sub>6</sub>(ox)}<sub><i>n</i></sub> chains, which are also extended into a 3D microporous framework linked by the bdt ligands. Their frameworks can be simplified as the same topological network (4<sup>6</sup>,6<sup>6</sup>,8<sup>3</sup>)­(4<sup>2</sup>,6<sup>3</sup>,8). The substructure of the 1D {Fe­(tz)<sub>3</sub>}<sub><i>n</i></sub> chain in <b>1</b>·13H<sub>2</sub>O consists of spin-crossover (SCO) active Fe1 ions and low spin (LS) Fe2 ions alternately, while the trinuclear unit in <b>2</b>·solvent contains a partial high spin (HS) Fe1 ion and two terminal HS Fe2 ions. Magnetic susceptibility measurements reveal that complex <b>1</b>·13H<sub>2</sub>O presents an incomplete gradual SCO behavior. Although complex <b>2</b>·solvent also has the SCO active Fe1 ions, the spin state change is extremely small and the antiferromagnetic property is primarily observed
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