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

Coordination compounds of the ligand 1,6-bis(3,5-dimethyl-1-pyrazolyl)-2,5-dithiahexane (bddh) with divalent nickel, cobalt and zinc salts. X-ray crystal structure of Co(bddh)(NCS)2

SYNTHESIS AND STRUCTURE OF (NI3(μ3-S)(O-(SCH2)2C6H4)3)2-, A NEW TYPE OF TRINUCLEAR NICKEL-SULFIDE-THIOLATE CLUSTER

Die Reaktion der Ionen TcO und ReO mit Schwefelwasserstoff in wasriger Losung wird mit Hilfe von Elektronenabsorptionsspektren untersucht. An Hand eines einfachen MO-Diagramms konnte die Existenz des ReS-Ions in Losung nachgewiesen werden. Das Elektronenabsorptionsspektrum des Tetrathioperrhenat-Ions wurde zugeordnet. Im Falle des TcO-Ions bildet sich moglicherweise in geringer Menge TcO3S−.



The reaction of the ions TcO and ReO with hydrogen sulfide in aqueous solution is investigated by measuring the electronic absorption spectra. Using a simple MO diagram the existence of the ReS-ion in solution is proved. The electron absorption spectrum of the tetrathioperrhenate ion is assigned. Small amounts of TcO3S− are possibly formed by the reaction of TcO with H2S.

Die Reaktion von TcO 4− und ReO 4− mit Schwefelwasserstoff Darstellung des Tetrathioperrhenat‐Ions in Lösung

Hitherto unknown 1,2,3-triphosphetenes RCPPCF3PCF3 (3a–d) are formed as main products in reactions of phosphaalkynes RCP [R = iPr2N (1a), tBu (1b), Me2EtC (1c), 1-methylcyclohexyl (1d)] with the cyclotetraphosphane (PCF3)4 (2). According to NMR results the CF3 groups in 3a–d have a trans disposition; an X-ray diffraction study of 3a confirms this structure. The PP bond lengths in 3a are equal [2.201 (2) and 2.204 (2) A] and correspond to single bonds. A considerable shortening is observed for the sp2-C–N bond (1.336 A) which, together with the elongation of the PC bond (1.746 A), indicates effective π donation of the lone pair on nitrogen. Surprisingly, 3a can be prepared in quantitative yields by reaction of the PP ylide Me3PPCF3 (6) with 1 a (molar ratio: 2:1). In contrast, the corresponding reactions of 6 with the alkyl-substituted phosphaalkynes 1b–d lead to the novel phosphorus ylides Me3PC(R)PPCF3PCF3PCF3 [R = tBu (10a), Me2EtC (10b), 1-methylcyclohexyl (10c)] in good yields. In their molecular groundstate structures, determined by X-ray diffraction, the lone pair on the phosphano P atom prefers the syn position with respect to the ylidic PC bond. An unusual lengthening of the sp2-C–C bond [1.553 (4) (10a), 1.543 (6) (10b), 1.551 (4) A (10c)] to values typical for sp3-C/sp3-C distances is observed.

1,2,3‐Triphosphetenes, First Examples of a New Class of Phosphorus Heterocycles

in acetonitrile, a Hammett plot showed a linear relationship between Hammett u, values and the second reduction potential, indicating that electron density changes on the ligand are transmitted to the metal ions.'O Replacement of the 4-methyl ring substituent by CF3 in I and I1 has been shown to increase Elp for both one-electron-reduction steps in DMF by 0 . 1 4 4 1 9 V, clearly indicating the transmission of a distant electron-withdrawing effect to the copper centers." The wide separation of the two reduction waves of all these compounds indicates significant stability for the one-electron intermediates, as is indicated by the large conproportionation constants (Table VII). The one-electron-reduced species derived from I exhibits a seven-line EPR spectrum at room temperature in both CH2C12 and CH3CN, indicative of interaction of the odd electron with both copper Compound I1 produces a one-electron-reduced species in CH3CN, which also exhibits a seven-line spectrum (Figure 6). The analogous copper tetrafluoroborate complex involving the butylene-bridged macrocyclic ligand derived from 4-tert-butyl-2,6-diformylphenol has also been shown to produce a one-electron-reduced species in CH2C12 or acetone, which exhibits a seven-line spectrum at room temperature." This behavior contrasts with that associated with I11 and IV, which exhibit four-line ~pectra.~*~O Acknowledgment. We thank the Natural Sciences and Engineering Research Council of Canada for financial support for this study, including the purchase of the variable-temperature Faraday susceptometer and EPR spectrometer.

Bernt Krebs

Papers

Coordination compounds of the ligand 1,6-bis(3,5-dimethyl-1-pyrazolyl)-2,5-dithiahexane (bddh) with divalent nickel, cobalt and zinc salts. X-ray crystal structure of Co(bddh)(NCS)2

SYNTHESIS AND STRUCTURE OF (NI3(μ3-S)(O-(SCH2)2C6H4)3)2-, A NEW TYPE OF TRINUCLEAR NICKEL-SULFIDE-THIOLATE CLUSTER

Die Reaktion von TcO 4− und ReO 4− mit Schwefelwasserstoff Darstellung des Tetrathioperrhenat‐Ions in Lösung

1,2,3‐Triphosphetenes, First Examples of a New Class of Phosphorus Heterocycles

Preparation, structure, and properties of manganese toluene-3,4-dithiolate complexes in different oxidation states