The chemistry of graphene oxide is discussed in this critical review Particular emphasis is directed toward the synthesis of graphene oxide, as well as its structure Graphene oxide as a substrate for a variety of chemical transformations, including its reduction to graphene-like materials, is also discussed This review will be of value to synthetic chemists interested in this emerging field of materials science, as well as those investigating applications of graphene who would find a more thorough treatment of the chemistry of graphene oxide useful in understanding the scope and limitations of current approaches which utilize this material (91 references)

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The chemistry of graphene oxide

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

The hydrogen bond is the most important of all directional intermolecular interactions. It is operative in determining molecular conformation, molecular aggregation, and the function of a vast number of chemical systems ranging from inorganic to biological. Research into hydrogen bonds experienced a stagnant period in the 1980s, but re-opened around 1990, and has been in rapid development since then. In terms of modern concepts, the hydrogen bond is understood as a very broad phenomenon, and it is accepted that there are open borders to other effects. There are dozens of different types of X-H.A hydrogen bonds that occur commonly in the condensed phases, and in addition there are innumerable less common ones. Dissociation energies span more than two orders of magnitude (about 0.2-40 kcal mol(-1)). Within this range, the nature of the interaction is not constant, but its electrostatic, covalent, and dispersion contributions vary in their relative weights. The hydrogen bond has broad transition regions that merge continuously with the covalent bond, the van der Waals interaction, the ionic interaction, and also the cation-pi interaction. All hydrogen bonds can be considered as incipient proton transfer reactions, and for strong hydrogen bonds, this reaction can be in a very advanced state. In this review, a coherent survey is given on all these matters.

The hydrogen bond in the solid state.

The transition metal dichalcogenides are about 60 in number. Two-thirds of these assume layer structures. Crystals of such materials can be cleaved down to less than 1000 A and are then transparent in the region of direct band-to-band transitions. The transmission spectra of the family have been correlated group by group with the wide range of electrical and structural data available to yield useful working band models that are in accord with a molecular orbital approach. Several special topics have arisen; these include exciton screening, d-band formation, and the metal/insulator transition; also magnetism and superconductivity in such compounds. High pressure work seems to offer the possibility for testing the recent theory of excitonic insulators.

The transition metal dichalcogenides discussion and interpretation of the observed optical, electrical and structural properties

Copper is an essential trace element in living systems, present in the parts per million concentration range. It is a key cofactor in a diverse array of biological oxidation-reduction reactions. These involve either outer-sphere electron transfer, as in the blue copper proteins and the Cu{sub A} site of cytochrome oxidase and nitrous oxide redutase, or inner-sphere electron transfer in the binding, activation, and reduction of dioxygen, superoxide, nitrite, and nitrous oxide. Copper sites have historically been divided into three classes based on their spectroscopic features, which reflect the geometric and electronic structure of the active site: type 1 (T1) or blue copper, type 2 (T2) or normal copper, and type 3 (T3) or coupled binuclear copper centers. 428 refs.

Multicopper Oxidases and Oxygenases

SN Ring with Di‐, Tri‐, and Tetra‐Coordinated Sulfur Atoms by Nucleophilic Substitution

The invention is directed to manganese-containing polyoxometallates of the formula (1) (Q).sub.q (Mn.sub.p A.sub.a X.sub.x Y.sub.y M.sub.m O.sub.d Z.sub.z (H 2 O) b )cH 2 O (1) where Q is one or more cations selected from the group consisting of H, Li, K, Na, Rb, Cs, Ca, Mg, Sr, Ba, Al, PR 1 R 2 R 3 R 4 and NR 1 R 2 R 3 R 4 where R 1 , R 2 , R 3 and R 4 =H or C 1 -C 20 -alkyl, C 5 -C 8 -cycloalkyl or aryl; Mn is manganese; A is a heterometal and is one or more transition metals from transition groups II to VIII apart from Zn, in particular Ru, V, Ti, Zr, Cr, Fe, Co, Cu, Sn, Ni, Re or Os; X is one or more elements selected from the group consisting of Ga, B, P, Si, Ge, As, F, Cl, Br and I; Y is Sb, S, Te, Se and Bi; M is one or more transition metals selected from the group consisting of Mo, W, Nb, Ta and V; Z is one or more anions selected from the group consisting of OH - , F - , Cl - , Br - , I - , N 3 - , NO 3 - , ClO 4 - , NCS--, SCN--, PF 6 - , RSO 3 - , RSO 4 - , CF 3 SO 3 - , BR 4 - , BF 4 - , OAc - , where R=H, C 1 -C 20 -alkyl, C 5 -C 8 -cycloalkyl or aryl. The indexes q, p, a, x, y, m, d, z and the numbers b and c are defined in the specification. The oxidation catalyst according to the invention is particularly effective in activating peroxidic compounds and oxygen.

Manganiferous polyoxometallates, synthesis and use thereof

The title compound [H 7 O 3 (bis-dibromo-dibenzo-30-crown-10)][Se 2 Br 9 ].1.5CH 2 Cl 2 (1) was isolated from a solution of SeBr 4 and dibenzo-30-crown-10 in CH 3 CN/CH 2 Cl 2 containing a small amount of hydrobromic acid. During the reaction the crown ether is brominated by HBr. The compound crystallizes in the monoclinic space group P2 1 /n with a = 17.688(11), b = 14.921(6), c = 20.521(12) A, β = 97.71(5)°, and Z = 4. 1 is a novel example in the series of supramolecular halogenochalcogeno acids prepared in our group in which different oxonium cations are stabilized and encapsulated by crown ethers. Especially in this class of superacids complexation by cyclic polyethers offers covenient and variable possibilities for the controlled synthesis of oxonium cations. In the present case the large dibenzo-30-crown-10 ring systems are able to stabilize trinuclear [H 7 O 3 ] + cations within their cavities. Besides the macromolecular cations and some dichloromethane solvent molecules, the crystal structure of 1 contains molecular [Se 2 Br 9 ] - ions with approximate D 3 h symmetry, each consisting of two face-sharing SeBr 6 octahedra.

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A Novel Crown-Ether Stabilized Oxonium Halogenochalcogenate(IV): [H7O3(Bis-dibromo-dibenzo-30-crown-10)][Se2Br9]·1.5CH2Cl2

Wie kürzlich von R a b e n a u und Mitarbb.2 gezeigt wurde, entstehen beim Tempern von Gemischen Blei­ halogenid — Bleichalkogenid die stabilen ternären Chalkogenid-halogenide Pb4SeBr6 , Pb5S2J6 und Pb7S2Br10 . Das metastabile Pb4SCl6 wird beim Abschrecken einer Schmelze dieser Zusammensetzung von 600 °C er­ halten. Diese Verbindungen stellen Vertreter einer neuen Verbindungsklasse des Bleis dar. Einkristalle konnten durch Reaktion des entsprechenden Chalkogenids mit konz. Halogenwasserstofflösungen unter hy­ drothermalen Bedingungen hergestellt werden. Wir haben diese für die Strukturchemie des Bleis und die Systematik der Chalkogenidhalogenide wichtigen Ver­ bindungen durch vollständige Röntgenstrukturanalysen untersucht. Pb4SeBr6 kristallisiert orthorhombisch in der Raum­ gruppe Imm2 — Cf® mit c = 4,361 (2), 6 = 15,780(8), c = 9,720(5) Ä, Z = 2, dx = 6,886, dexp. = 6,84 g/cm3. Pb5S2J6 bildet eine monokline Struktur (Raumgruppe C2]m -C lh) mit a = 14,338 (7), 6 = 4,437(2), c = 14,552(7)Ä, /J = 98,04(5)°, Z = 2, dx = 6,743, dexv.=

Strukturchemie von Chalkogenid-halogeniden: Die Kristallstrukturen von Pb4SeBr6 und Pb5S2J6

C15H24O2,M=236.2, monoclinic, P 21,a=7.229(7),b=14.925 (9),c=6.235 (9) A, β=92.40 (9)°,V=672.1 A3,T=−133 °C,Z=2,D
x=1.17 g cm−3. The X-ray diffraction analysis of this sesquiterpenoid fromCarissa opaca confirmed the previously proposed constitution of the isolate and, furthermore, allowed precise NMR assignment.

Bernt Krebs

Papers

SN Ring with Di‐, Tri‐, and Tetra‐Coordinated Sulfur Atoms by Nucleophilic Substitution

Manganiferous polyoxometallates, synthesis and use thereof

A Novel Crown-Ether Stabilized Oxonium Halogenochalcogenate(IV): [H7O3(Bis-dibromo-dibenzo-30-crown-10)][Se2Br9]·1.5CH2Cl2

Strukturchemie von Chalkogenid-halogeniden: Die Kristallstrukturen von Pb4SeBr6 und Pb5S2J6

Natural product chemistry, part 100: The structure of carissone, C 15 H 24 O 2