24 research outputs found
好アルカリ性Bacillus A-007株のK^+ : 促進ATPaseについて
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
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
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
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
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)
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
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
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
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
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