Structure and Magnetism of [<i>n</i>-BuNH₃]₁₂[Cu₄(GeW₉O₃₄)₂]·14H₂O Sandwiching a Rhomblike Cu₄⁸⁺ Tetragon through α-Keggin Linkage

A sandwich-type polyoxometalate, [Cu₄(GeW₉O₃₄)₂]¹²⁻ (<b>1a</b>), in which two B-α-[GeW₉O₃₄]¹²⁻ ligands sandwich a rhomblike Cu₄⁸⁺ tetragon through α-Κeggin linkage, is first isolated as a [<i>n</i>-BuNH₃]⁺ salt, [<i>n</i>-BuNH₃]₁₂[Cu₄(GeW₉O₃₄)₂]·14H₂O (<b>1</b>). A Cu₄O₁₄ cluster for the rhomblike Cu₄⁸⁺ tetragon in <b>1a</b> with <i>C</i>_2<i>h</i> local symmetry consists of two Jahn−Teller (JT) distorted CuO₆ octahedra (at internal sites) with a short diagonal Cu_int···Cu_int distance of 3.10−3.11 Å and two CuO₅ square pyramids (at external site) with a long diagonal Cu_ext···Cu_ext distance of 5.34−5.35 Å, the feature of which is different from [Cu₄(H₂O)₂(GeW₉O₃₄)₂]¹²⁻ (<b>2a</b>), comprising the four JT-distorted CuO₆ octahedral Cu₄⁸⁺ tetragons through β-Keggin linkage: the axial Cu_ext−O bond distance (2.27−2.29 Å) for <b>1a</b> is shorter than the corresponding JT-axial distance (2.36 Å) for <b>2a</b>. Measurements of magnetic susceptibility, magnetization, and electron spin resonance spectroscopy for <b>1</b> are carried out for better understanding of the molecular magnetism of the Cu₄⁸⁺ tetragon in comparison with <b>2a</b>. The analysis of the magnetic behavior, based on the isotropic Heisenberg spin Hamiltonian comprising three exchange parameters (<i>J</i>, <i>J′</i>, and <i>J′′</i>), gives <i>J</i> = −24.1 cm⁻¹ for the Cu_ext··Cu_int sides, <i>J′</i> = −99.1 cm⁻¹ for the Cu_int···Cu_int diagonal, and <i>J′′</i> = +0.04 cm⁻¹ for the Cu_ext···Cu_ext diagonal of the Cu₄⁸⁺ rhombus. The <i>S</i> = 1 ground state of <b>1</b> displays <u><i>g</i></u>_|| = 2.42, <i>g</i>_⊥= 2.07, <i>D</i> = −1.44 × 10⁻² cm⁻¹, and |<i>A</i>_Cu||| = 46.5 × 10⁻⁴ cm⁻¹. An observation of the asymmetric magnetization between a positive and a negative pulsed field (up to 10³ T/s) at 0.5 K on the hysteresis loop indicates the quantum tunneling at zero field. The magnetic exchange interactions of four unpaired d_{<i>x</i>²−<i>y</i>²}-electron spins are discussed in terms of the point-dipole approximation, and the primary contribution to <i>D</i> is implied to come from the magnetic dipole−dipole interaction between two spins at the Cu_ext centers

Structure and Magnetism of [<i>n</i>-BuNH₃]₁₂[Cu₄(GeW₉O₃₄)₂]·14H₂O Sandwiching a Rhomblike Cu₄⁸⁺ Tetragon through α-Keggin Linkage

A sandwich-type polyoxometalate, [Cu₄(GeW₉O₃₄)₂]¹²⁻ (<b>1a</b>), in which two B-α-[GeW₉O₃₄]¹²⁻ ligands sandwich a rhomblike Cu₄⁸⁺ tetragon through α-Κeggin linkage, is first isolated as a [<i>n</i>-BuNH₃]⁺ salt, [<i>n</i>-BuNH₃]₁₂[Cu₄(GeW₉O₃₄)₂]·14H₂O (<b>1</b>). A Cu₄O₁₄ cluster for the rhomblike Cu₄⁸⁺ tetragon in <b>1a</b> with <i>C</i>_2<i>h</i> local symmetry consists of two Jahn−Teller (JT) distorted CuO₆ octahedra (at internal sites) with a short diagonal Cu_int···Cu_int distance of 3.10−3.11 Å and two CuO₅ square pyramids (at external site) with a long diagonal Cu_ext···Cu_ext distance of 5.34−5.35 Å, the feature of which is different from [Cu₄(H₂O)₂(GeW₉O₃₄)₂]¹²⁻ (<b>2a</b>), comprising the four JT-distorted CuO₆ octahedral Cu₄⁸⁺ tetragons through β-Keggin linkage: the axial Cu_ext−O bond distance (2.27−2.29 Å) for <b>1a</b> is shorter than the corresponding JT-axial distance (2.36 Å) for <b>2a</b>. Measurements of magnetic susceptibility, magnetization, and electron spin resonance spectroscopy for <b>1</b> are carried out for better understanding of the molecular magnetism of the Cu₄⁸⁺ tetragon in comparison with <b>2a</b>. The analysis of the magnetic behavior, based on the isotropic Heisenberg spin Hamiltonian comprising three exchange parameters (<i>J</i>, <i>J′</i>, and <i>J′′</i>), gives <i>J</i> = −24.1 cm⁻¹ for the Cu_ext··Cu_int sides, <i>J′</i> = −99.1 cm⁻¹ for the Cu_int···Cu_int diagonal, and <i>J′′</i> = +0.04 cm⁻¹ for the Cu_ext···Cu_ext diagonal of the Cu₄⁸⁺ rhombus. The <i>S</i> = 1 ground state of <b>1</b> displays <u><i>g</i></u>_|| = 2.42, <i>g</i>_⊥= 2.07, <i>D</i> = −1.44 × 10⁻² cm⁻¹, and |<i>A</i>_Cu||| = 46.5 × 10⁻⁴ cm⁻¹. An observation of the asymmetric magnetization between a positive and a negative pulsed field (up to 10³ T/s) at 0.5 K on the hysteresis loop indicates the quantum tunneling at zero field. The magnetic exchange interactions of four unpaired d_{<i>x</i>²−<i>y</i>²}-electron spins are discussed in terms of the point-dipole approximation, and the primary contribution to <i>D</i> is implied to come from the magnetic dipole−dipole interaction between two spins at the Cu_ext centers

Kinetic study of the quenching reaction of singlet oxygen by α-, β-, γ-, δ-tocotrienols, and palm oil and soybean extracts in solution

<div><p>Measurements of the singlet oxygen (¹O₂) quenching rates (<i>k</i>_<i>Q</i> (<i>S</i>)) and the relative singlet oxygen absorption capacity (SOAC) values were performed for 11 antioxidants (AOs) (eight vitamin E homologues (α-, β-, γ-, and δ-tocopherols and -tocotrienols (-Tocs and -Toc-3s)), two vitamin E metabolites (α- and γ-carboxyethyl-6-hydroxychroman), and trolox) in ethanol/chloroform/D₂O (50:50:1, v/v/v) and ethanol solutions at 35 °C. Similar measurements were performed for five palm oil extracts 1–5 and one soybean extract 6, which included different concentrations of Tocs, Toc-3s, and carotenoids. Furthermore, the concentrations (wt%) of Tocs, Toc-3s, and carotenoids included in extracts 1–6 were determined. From the results, it has been clarified that the ¹O₂-quenching rates (<i>k</i>_<i>Q</i> (<i>S</i>)) (that is, the relative SOAC value) obtained for extracts 1–6 may be explained as the sum of the product {Σ <i>k</i>_<i>Q</i>^AO-<i>i</i> (<i>S</i>) [AO-<i>i</i>]/100} of the rate constant (<i>k</i>_<i>Q</i>^AO-<i>i</i> (<i>S</i>)) and the concentration ([AO-<i>i</i>]/100) of AO-<i>i</i> (Tocs, Toc-3s, and carotenoid) included.</p></div

Kinetic study of the quenching reaction of singlet oxygen by seven rice bran extracts in ethanol solution. Development of a singlet oxygen absorption capacity (SOAC) assay method

<p>Measurements of singlet oxygen (¹O₂) quenching rates (<i>k</i>_Q (<i>S</i>)) and the relative singlet oxygen absorption capacity (SOAC) values were performed for seven rice bran extracts 1–7, which contained different concentrations of antioxidants (AOs) (such as α-, β-, γ-, and δ-tocopherols and -tocotrienols, three carotenoids (lutein, β-carotene, and zeaxanthin), and γ-oryzanol), in ethanol at 35 °C using UV–vis spectrophotometry. The concentrations of four tocopherols and four tocotrienols, three carotenoids, and γ-oryzanol contained in the extracts were determined using HPLC-MS/MS, UV-HPLC, and UV–vis absorption spectroscopy, respectively. Furthermore, comparisons of <i>k</i>_Q (<i>S</i>) (Obsd.) values observed for the above extracts 1–7 with the sum of the product { [AO-<i>i</i>]} of the values obtained for each AO-<i>i</i> and the concentration ([AO-<i>i</i>]) of AO-<i>i</i> contained in extracts 1–7 were performed. From the results, it has been ascertained that the SOAC method is applicable to general food extracts to evaluate their ¹O₂-quenching activity.</p> <p>Measurements of the quenching rate (<i>k</i>_Q) of singlet oxygen were performed for seven rice bran extracts in ethanol to evaluate their singlet oxygen quenching activity.</p

Lipidated Brartemicin Analogues Are Potent Th1-Stimulating Vaccine Adjuvants

Effective Th1-stimulating vaccine adjuvants typically activate antigen presenting cells (APCs) through pattern recognition receptors (PRRs). Macrophage inducible C-type lectin (Mincle) is a PRR expressed on APCs and has been identified as a target for Th1-stimulating adjuvants. Herein, we report on the synthesis and adjuvanticity of rationally designed brartemicin analogues containing long-chain lipids and demonstrate that they are potent Mincle agonists that activate APCs to produce inflammatory cytokines in a Mincle-dependent fashion. Mincle binding, however, does not directly correlate to a functional immune response. Mutation studies indicated that the aromatic residue of lead compound <b>9a</b> has an important interaction with Mincle Arg183. In vivo assessment of <b>9a</b> highlighted the capability of this analogue to augment the Th1 response to a model vaccine antigen. Taken together, our results show that lipophilic brartemicin analogues are potent Mincle agonists and that <b>9a</b> has superior in vivo adjuvant activity compared to TDB