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

[Mn(S2C6H3Me)2]n−: Mononuclear Manganese Complexes with Square‐Planar (n = 1) and Distorted Tetrahedral (n = 2) Sulfur Coordination

Komplex‐Stabilisierung eines Aminooxophosphans (Phosphinidenoxids)

Cs2B2S4 (I41/acd; a = 7,270(1) A, c = 35,737(7) A; Z = 8; Subzelle: I4/mmm; a′ = 5,141(1) A, c′ = 17,868(4) A, Z = 2) wird durch Reaktion von Caesiumsulfid Cs2S mit amorphem Bor und elementarem Schwefel im Verhaltnis 1:2:3 bei einer Reaktionstemperatur von 600°C mit anschliesendem Tempern dargestellt. Die Kristallstruktur besteht aus molekularen, planaren [B2S4]2−-Einheiten mit extrem gespannten [B2S2]-Vierringen, zwischen denen sich die neunfach koordinierten Alkalimetallkationen befinden. Das Strukturmotiv zweier kantenverknupfter BS3-Gruppen wird hier erstmals in der Chemie der Thioborate isoliert beobachtet, ist jedoch als Baustein des polymeren Bor-Schwefel-Gerusts im B2S3 bekannt.



Cs2B2S4 – A Derivative of the Dimeric Metathioboric Acid



Cs2B2S4 (structure: I41/acd; a = 7.270(1) A, c = 35.737(7) A; Z = 8; substructure: I4/mmm; a′ = 5.141(1) A, c′ = 17.868(4) A, Z = 2) is prepared by the reaction of cesium sulfide with stoichiometric amounts of boron and sulfur (effective molar ratio M:B:S = 2:2:4) at 600°C and subsequent annealing. The crystal structure contains isolated [B2S4]2− groups consisting of four-membered B2S2 rings with two exocyclic sulfur atoms on each of the boron atoms. The cesium cations are nine-coordinate between these rings. The structural feature of two edge-sharing BS3 groups forming an isolated anion appears for the first time in thioborate chemistry, although it is known as a part of the polymeric network in B2S3.

Cs2B2S4 – Ein Salz der dimeren Metathioborsäure†

The reaction of bis(trifluoromethyl)arsane 2 with secondary amines R2NH in a molar ratio of 1:3 at -60 °C allows the preparation of trifluoromethyl arsaalkenes of the type F3CAs=C(F)NR2 in moderate yields (15-35%) [NR2 = NMe2 (3a), NMeEt (3b), NEt2 (3c)]. The main product of the reaction of 2 with Me2NH is the 1,1-diamino compound F3CAs=C(NMe2)2 (4a). With ethyl(isopropyl)- or di(isopropyl)amine the corresponding derivatives F3CAs=C(F)NEt(iPr) (3d) and F3CAs=C(F)N(iPr)2 (3e), respectively, are formed only in traces (3d), or not at all (3 e). However, 3d and 3e can be prepared by reacting perfluoro-2-arsapropene with the corresponding secondary amines. The new compounds 3 a to 3 e can be stored at 20 °C in chloroform solution for hours without decomposition and show Z configuration without exception. The molecular structure of 1-(diethylamino)-1,3,3,3-tetrafluoro-2-arsapropene 3c, determined by an X-ray diffraction study on single crystals, indicates a strong electronic interaction of the lone pair on nitrogen with the AsC double bond. This results in a trigonal planar arrangement at the nitrogen atom, a strongly shortened sp2-CN-bond (1.312 Å), an elongated AsC distance (1.867 Å), and an almost planar skeleton of the molecule.

Reaktive E=C (p-p)π-Systeme, XL. / Reactive E=C(p-p)π Systems, XL.

Synthesis, spectroscopic characterisation, and single-crystal structure analyses are described for a number of CuI and CuII co-ordination compounds with the ligand 1,8-bis[bis(1′-methyl-benzimidazol-2′-ylmethyl)amino]-3,6-dioxaoctane (L). The compounds have the general formulae Cu2(L)X2Y2·xS, Cu(L)Y, Cu2(L)(CO)2Y2, Cu2(L)(Z)Y3, and Cu2(L)X2, where X = F, Cl, Br, or I; Y = ClO4, BF4, CF3SO3, Cl, or Br; Z = bridging anion like benzotriazolate; and S = solvent. Single-crystal structures of three CuII compounds, [Cu2(L)F2][BF4]2·2H2O·H2OBF3(1), [Cu2(L)Cl2]Cl2·6H2O (2), and [Cu2(L)Br2][CF3SO3]2·EtOH (3) have been determined using diffractometer data. All three compounds contain the dinuclear unit [XCu(L)CuX]2+ in which the ligand L bridges the two Cu–X fragments. However, the intramolecular Cu ⋯ Cu distances are very large (i.e. larger than 575 pm). The intermolecular Cu ⋯ Cu contacts are much shorter, being 481, 388–488, and 398–405 pm, for (1), (2), and (3), respectively. Ligand-field, e.s.r., n.m.r., and i.r. spectra have been used to characterise all the compounds. The ligand-field maxima all agree with square-pyramidal CuII with a CuN3XO chromophore in which X = F, Cl, or Br, respectively. The e.s.r. spectra indicate that exchange effects (intermolecularly) are important, resulting even in exchange-narrowed signals. Only the compounds Cu2(L)(Z)Y3 exhibit e.s.r. spectra typical for dinuclear CuII systems. The observed νCO bands at ca. 2 100 cm–1 for the CuI–CO adducts agree with end-on CO co-ordination.

Copper(I) and copper(II) compounds of a dinucleating, octadentate tetrakisbenzimidazole ligand. Crystal and molecular structures of three dihalogeno{1,8-bis[bis(1′-methylbenzimidazol-2′-ylmethyl)amino]-3,6-dioxaoctane}dicopper(II) bis(anion) compounds (halogen = F, Cl, or Br; anion = BF4, CF3SO3, or Cl)

Bernt Krebs

Papers

[Mn(S2C6H3Me)2]n−: Mononuclear Manganese Complexes with Square‐Planar (n = 1) and Distorted Tetrahedral (n = 2) Sulfur Coordination

Komplex‐Stabilisierung eines Aminooxophosphans (Phosphinidenoxids)

Cs2B2S4 – Ein Salz der dimeren Metathioborsäure†

Reaktive E=C (p-p)π-Systeme, XL. / Reactive E=C(p-p)π Systems, XL.