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Reactions of a series of unsymmetrically substituted N-heterocyclic carbene ligands with Ru3(CO)12afforded a variety of mononuclear (1, 2), trinuclear (3, 4, 5, and 5′), and tetranuclear (6, 7) ruthenium complexes via intramolecular ruthenium-mediated sp2and sp3C–H bond activations. Complexes 6and 7include an octahedral cluster skeleton consisting of four ruthenium atoms and two metalated carbon atoms. The formation of this type of ruthenium clusters is proposed to involve the initial C–C double-bond migration and subsequent sp2C–H bond activations. All new complexes were fully characterized, and the molecular structures of 1, 2, 5, 6, and 7were determined by X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Abstract: Early indica rice was chemically modified via acetylation to make modified food starch products with high contents of resistant starch. High contents of RS4 (type 4 resistant starch) of the products were measured. The result showed that the RS4 content increased obviously via acetylation. Acetylated starch was studied by FT-IR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy), XRD (X-ray diffraction) and DSC (differential scanning calorimetry). The starch granules were destroyed as observed by SEM. The X-ray diffraction data showed that the crystal structure of acetylated starch with low degree of substitution changed slightly and a part of crystallite structure (2θ 18°) was destroyed when the acetyl content was more than 3.25%. The heat of crystalloid fusion, gelatinization temperature, and gelatinization enthalpy all decreased (DSC) as the degree of substitution increased. SEM, XRD and DSC indicated that the resistance to enzymatic degradation of acetylated starch depended on the degree of substitution and the integrity of starch granules. [Copyright &y& Elsevier]

A series of molybdenum/tungsten polyoxometalate compounds, namely, [(MII(HL)2)Mo3O10] (M = Mn (1), Co (2), Ni (3)), [CuII2(L)2(HL)2]2(Mo8O26) (4), [Zn(HL)2(MoO4)]2·HL·4H2O (5), [CuII4(L)6WO4)]·3H2O (6) (HL = 3-(2-pyridyl)pyrazole), were designed and synthesized under hydrothermal conditions. X-ray diffraction analyses reveal that compounds 1−3have an isostructural wavelike chain structure consisting of the asymmetric building blocks of [Mo3O10], in which the ratio of octahedron {MoO6} and square pyramid {MoO5} is 1:2. The hexacoordinated transitional metal cation, just like one “anchor” to fix the above wavelike chain, is linked by two terminal oxygen atoms belonging to two edged asymmetric molybdate [Mo3O10]2−units, and further chelated by two 3-(2-pyridyl)pyrazole ligands. Although a similar synthetic method in preparation of 1−5was employed, compounds 4and 5show a completely different structure compared to compounds 1−3. Compound 4is composed of two separate parts of the [CuII2(L)2(HL)2]2+dimer and the ε-[Mo8O26]4−unit. Compound 5consists of a bimetallic tetranuclear cluster that is constructed from corner-sharing {MoO4} tetrahedra and {ZnN4O2} distorted octahedron forming a cyclic {Zn2Mo2O4} core. For compound 6, a one-dimensional structure is composed of WO42−linked by the centrosymmetric tetranuclear copper grids, in which two approximately planar [CuII(L)]2units with an inversion center stack parallel and face-to-face linked by two additional deprotonated ligands of L−1perpendicularly. [ABSTRACT FROM AUTHOR]