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

Durch Symproportionierung von elementarem Selen und SeCl4 in polaren protischen Losungsmitteln gelang die Stabilisierung der neuartigen. Halogenoselenat(+II)-Anionen [SeCl4]2− und [Se2Cl6]2− und ihre Kristallisation mit grosen organischen Kationen. Die Anionen wurden durch vollstandige Rontgenstrukturanalysen charakterisiert. Das gelb-orange [Ph3(C2H4OH)P]2[SeCl4] · MeCN (Raumgruppe P1, a = 10,535(4), b = 12,204(5), c = 16,845(6) A, α = 77,09(3)°, β = 76,40(3)°, γ = 82,75(3)° bei 140 K) enthalt in der Kristallstruktur monomere [SeCl4]2−-Anionen mit quadratisch-planarer Koordination am Se(+II). Die mittlere SeCl-Bindungslange betragt 2,441 A. Im gelben [Ph4P]2[Se2Cl6] (Raumgruppe P1, a = 10,269(3), b = 10,836(4), c = 10,872(3) A, α = 80,26(3)°, β = 79,84(2)°, γ = 72,21(3)° bei 140 K) wird ein dinucleares zentrosymmetrisches [Se2Cl6]2−-Ion, ebenfalls mit quadratisch-planar koordiniertem Selen(+II), beobachtet. Die mittleren terminalen bzw. verbruckenden SeCl-Abstande betragen 2,273 bzw. 2,680 A. Durch Redox-Reaktionen von elementarem Selen mit Boranat/Thiolat in Ethanol/DMF konnte das Bis(pentaselenido)selenat(+II)-Anion [Se(Se5)2]2− als neuer Typ eines gemischtvalenten Chalkogenids dargestellt werden. Im dunkel-rotbraunen [Ph4P]2[Se(Se5)2] (Raumgruppe P21/n, a = 12,748(4), b = 14,659(5), c = 14,036(5) A, β = 108,53(3)° bei 140 K) liegt ein zentrosymmetrisches molekulares [Se(Se5)2]2−-Ion mit quadratisch-planarer Koordination des zentralen Se(+II) durch zwei zweizahnig gebundene [Se5]2−-Einheiten vor (mittlere SeSe-Bindungslangen: 2,658 A am Se(+II), 2,322 A im [Se5]2−). Die entstehenden sechsgliedrigen, uber das zentrale Se(+II) spirocyclisch verbundenen Chelatringe haben Sesselkonformation. Uber schwingungsspektroskopische Untersuchungen der neuen Anionen wird berichtet.



Chloro- and Polyselenoselenates(II): Synthesis, Structure, and Properties of [Ph3(C2H4OH)P]2[SeCl4] · MeCN, [Ph4P]2[Se2Cl6], and [Ph4P]2[Se(Se5)2]



By symproportionation of elemental selenium and SeCl4 in polar protic solvents the novel chloroselenates(+II), [SeCl4]2− and [Se2Cl6]2−, could be stabilized; they were crystallized with voluminous organic cations. They were characterized from complete X-ray structure analysis. Yellow-orange [Ph3(C2H4OH)P]2[SeCl4] · MeCN (space group P1, a = 10.535(4), b = 12.204(5), c = 16.845(6) A, α = 77.09(3)°, β = 76.40(3)°, γ = 82.75(3)° at 140 K) contains in its crystal structure monomeric [SeCl4]2− anions with square-planar coordination of Se(+II). The mean SeCl bond length is 2.441 A. In yellow [Ph4P]2[Se2Cl6] (space group P1, a = 10.269(3), b = 10.836(4), c = 10.872(3) A, α = 80.26(3)°, β = 79.84(2)°, γ = 72.21(3)° at 140 K) a dinuclear centrosymmetric [Se2Cl6]2− anion, also with square-planar coordinated Se(+II), is observed. The average terminal and bridging SeCl bond distances are 2.273 and 2.680 A, respectively. From redox reactions of elemental Se with boranate/thiolate in ethanol/DMF the bis(pentaselenido)selenate(+II) anion [Se(Se5)2]2− was prepared as a novel type of a mixed-valent chalcogenide. In dark-red-brown [Ph4P]2[Se(Se5)2] (space group P21/n, a = 12.748(4), b = 14.659(5), c = 14.036(5) A, β = 108.53(3)° at 140 K) centrosymmetric molecular [Se(Se5)2]2− anions with square-planar coordination of the central Se(+II) by two bidentate pentaselenide ligands is observed (mean SeSe bond lengths: 2.658 A at Se(+II), 2.322 A in [Se5]2−). The resulting six-membered chelate rings with chair conformation are spirocyclically linked through the central Se(+II). The vibrational spectra of the new anions are reported.

Chloro‐ und Polyselenoselenate(II) Darstellung, Struktur und Eigenschaften von [Ph3(C2H4OH)P]2[SeCl4] · MeCN, [Ph4P]2[Se2Cl6] und [Ph4P]2[Se(Se5)2]

A remarkable anion effect on the crystal packing of two analogous copper complexes from a thiophene-containing phenol-based ligand

The reaction of the phenol-based ligand 4-methyl-2,6-bis{[(2-methylpyridyl)(2-methylthiophenyl)amino]methyl}phenol(Hpy2th2s), containing pyridine and thiophene substituents, with copper(II) chloride and bromide yields two new dinuclear complexes with the composition [Cu2(py2th2s)X3], where X = Cl or Br. In both complexes, the copper(II) ions are pentacoordinate and bridged by the deprotonated phenolate anion and by one halogen anion. Both complexes exhibit geometric asymmetry, as the coordination environment around one of the two copper ions is square-pyramidal, whereas the geometry around the other can be best described as a distorted trigonal bipyramid. The complexes were characterized by means of X-ray single-crystal diffraction, ligand field and EPR spectroscopy, mass spectrometry, and electrochemically. Magnetic susceptibility measurements indicate an antiferromagnetic coupling between the two metal centers (2J ≈ −200 cm−1). The interaction of the complexes with model substrates 3,5-di-tert-butylcatechol and tetrachlorocatechol is reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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Dinuclear CuII Complexes with a New Phenol-Based Ligand Bearing Pyridine and Thiophene Substituents: Synthesis, Characterization and Interaction with Catechol Substrates

Bernt Krebs

Papers

Chloro‐ und Polyselenoselenate(II) Darstellung, Struktur und Eigenschaften von [Ph3(C2H4OH)P]2[SeCl4] · MeCN, [Ph4P]2[Se2Cl6] und [Ph4P]2[Se(Se5)2]

A remarkable anion effect on the crystal packing of two analogous copper complexes from a thiophene-containing phenol-based ligand

Dinuclear CuII Complexes with a New Phenol-Based Ligand Bearing Pyridine and Thiophene Substituents: Synthesis, Characterization and Interaction with Catechol Substrates

Bridging the gap between polyoxometalates and classic coordination compounds: a novel type of hexavanadate complex.

The Crystal Structure of Mn2O7