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

The complex (Et4N )[Fe(SPh)2(NO)2] (2) has been obtained as black crystals by treatment of K[Fe4S3(NO)7]·H2O with potassium hydroxide in molten diphenyldisulfide and subsequent addition of methanol and tetraethylammonium chloride. 2 is orthorhombic, space group Pbca, Z = 8, with a = 18.853(3), b = 17.958(3), and c = 13.283(2) Å at 140 K. The X-ray structure of 2 has been refined to R1 (R2) = 2.7% (3.1% ). It reveals a pseudotetrahedral S2N2 arrangement around the iron atom (Fe -S 2.280, Fe -N 1.679 Å (mean values), S -Fe -S 109.73(2)°, N -Fe -N 117.36(9)°) and Fe -N -O groups of the linear type (N -O 1.180 Å , Fe -N - O 169.0° (mean values)). The N - O bond order is 2.2. Structural properties as well as the low Mößbauer isomeric shift ( + 0.08 mm/s relative to Fe metal) are indicative of strong Fe - N π-back bonding and a major contribution of the mesomeric form Fe = N = Ō̱ .

Synthese und Struktur von [Fe(SPh)2(NO)2]- dem „Monomeren“ des Roussinschen Phenylesters/ Synthesis and Structure of [Fe(SPh)2(NO)2]- , the “Monomer” of Roussin’s Phenyl Ester

Das fur gasformige halogen-gemischte Komplexe CoAl2ClnI8–n gemessene Spektrum liegt auf der Skala der Wellenzahlen zwischen denen von CoAl2Cl8 und CoAl2I8. Die molare Extinktion ist in allen drei Fallen von vergleichbarer Grose. Daraus ist zu schliesen, das die Koordination des Kobalts durch Halogen bei diesen Verbindungen verzerrt oktaedrisch ist.



Die Kristallstruktur von PdAl2Cl8 wurde mit Einkristallen bestimmt. Die Verbindung kristallisiert monoklin mit a = 6,583(3), b = 7,342(3), c = 13,033(5) A, β = 96,40(3)°; Raumgruppe P21/c. Es liegt ein Molekelgitter mit 2 PdAl2Cl8-Molekeln/Zelle vor. Pd ist quadratisch-planar von Cl umgeben.



Das Remissionsspektrum des festen PdAl2Cl8 stimmt mit dem Absorptionsspektrum der gasformigen Verbindung uberein.



Die Kristallstrukturen der Verbindungen MAl2Cl8, insbesondere der Zusammenhang der Struktur der Gasmolekel CoAl2Cl8 mit der bekannten Kristallstruktur dieser Verbindung werden behandelt.



A Contribution to the Coordination in the Gaseous MAl2Cl8 Complexes. Visible Spectrum of CoAl2ClnI8–n and Crystal Structure of PdAl2Cl8



The band wavenumbers in the visible spectrum of the mixed halogen complexes CoAl2ClnI8–n are observed between those of CoAl2Cl8 and CoAl2I8. The molar extinctions are comparable for all three cases. It can be concluded that the halogen coordination around cobalt is distorted octahedral.



The crystal structure of PdAl2Cl8 was determined from single crystals. The compound is monoclinic, space group P21/c, with a = 6,583(3), b = 7.342(3), c = 13.033(5) A, β = 96.40(3)°. The structure contains two molecular PdAl2Cl8 units per cell. Pd is in a tetragonal planar coordination of 4 Cl.



The remissionspectrum of solid PdAl2Cl8 corresponds to the spectrum of the gaseous compound. The crystal structures of the compounds MAl2Cl8 are discussed, especially the relationship of the structure of the gaseous molecule CoAl2Cl8 with the known crystal structure of this compound.

Ein Beitrag zu den Koordinationsverhältnissen in den gasförmigen MAI2Cl8‐Komplexen Das Spektrum von CoAl2ClnI8–n und die Kristallstruktur von PdAl2Cl8

A series of new lanthanide polyoxomolybdates was synthesised by reaction of lanthanide cations with the heptamolybdate anion (Mo7O24)6−. The heteropolyanions [Ln4(MoO4)(H2O)16(Mo7O24)4]14− (Ln = LaIII, CeIII, PrIII, SmIII, GdIII) were isolated as either their ammonium or tetramethylammonium salts and characterised by X-ray structure analysis, energy dispersive X-ray fluorescence analysis, and IR and Raman spectroscopy. The central [Ln4(MoO4)(H2O)16]10+ core of the anion is coordinated by four heptamolybdate groups. Each LnIII atom in the core exhibits ninefold coordination by oxygen atoms belonging to H2O, (MoO4)2− and (Mo7O24)6− units; the central molybdenum atom is coordinated tetrahedrally by four oxygen atoms. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Formation of Large Clusters in the Reaction of Lanthanide Cations with Heptamolybdate

Tripodliganden des Typs XM′ (OCH2PMe2)n(CH2CH2PMe2)3 – n (M′ = Si, Ge; n = 0 – 3) (1–6, Tab. 1) wurden in Kombination mit PPh3 bzw, PMe3 zur Darstellung neuer Tetraphosphankomplexe des Nickels genutzt. Die Vertreter LNiPPh3(7 – 12) sind durch Umsetzung von Ni(COD)2 (COD = 1,5-Cyclooctadien) mit den entsprechenden Liganden und PPh3 in Toluol in masigen Ausbeuten zuganglich. Die Synthese der Derivate LNiPMe3(13 – 18) gelingt z. T. (16 – 18) in Analogie zu den Ph3P-Komplexen; die Vertreter 13 – 16 sind in hoheren Ausbeuten durch Umsetzung von Ni(PMe3)4 mit den jeweiligen Liganden darstellbar. 13 – 18 lassen sich in der Regel nicht vollstandig von Nebenprodukten abtrennen. Der dreikernige Komplex FSi(CH2CH2PMe2)3[Ni(PMe2CH2CH2)3SiF]3(19) fallt im Gemisch mit 18 bei der Reaktion von Ni(COD)2 mit 6 und PMe3 an. Die neuen Verbindungen wurden (wenn moglich) durch analytische (C, H), generell aber durch spektroskopische Untersuchungen (IR; 1H-, 13C-, 19F-, 31P-NMR; MS) charakterisiert. Auf eine schwache, aber signifikante Ni Si-Wechselwirkung durch den Kafig weisen folgende Befunde hin: (1) Die grosen Tieffeldverschiebungen δδF von 35,2 ppm (12), 38,3 ppm (18) und 37,7 ppm (19); (2) 6J(PF)-Kopplungen [bzw. 3J(PNiSiF) durch den Kafig] von 6,0 Hz (12) und 7,6 Hz (18) sowie die Tieffeldverschiebung δδSi von 12,8 ppm (12); 3) die NiSi-Abstande von 3,95 A in 7 und 3,92 A in 12, verbunden mit einer deutlichen Stauchung der Kafige in Richtung der Ni ··· Si-Achse. Eine zusatzliche Entlastung des Ni von der hohen Ladungsdichte erfolgt durch π-Ruckbindung zu den Phosphanliganden.



Alternative Ligands. XXXII [1]. Novel Tetraphosphane Nickel Complexes with Tripod-Ligands of the Type XM′(OCH2PMe2)n(CH2CH2PR2)3 – n (M′ = Si, Ge; n = 0 – 3)



Tripod Ligands of the type XM′(OCH2PMe2)n(CH2CH2PMe23 – n (M′ = Si, Ge; n = 0 – 3) (1 – 6, Table 1) have been used together with PPh3 or PMe3 for the preparation of novel tetraphosphane complexes of Nickel. The representatives LNiPPh3 (7 – 12) are obtained by reaction of Ni(COD)2 (COD = 1,5-cyclooctadiene) with the corresponding ligands and PPh3 in toluene in moderate yields. The synthesis of the derivatives LNiPMe3 (13 – 18) is partly (16 – 18) accomplished in analogy to the Ph3P-complexes; compounds 13 – 16 are obtained in higher yields by reaction of Ni(PMe3)4 with the respective ligand. As a rule, 13 – 18 cannot be separated from by-products. The trinuclear complex FSi(CH2CH2PMe2)3[Ni(PMe2CH2CH2)3SiF]3 (19) is formed together with 18 in the reaction of Ni(COD)2 with 6 and PMe3. The new compounds have been characterized (if possible) by analytical (C, H), but in general by spectroscopic investigations (IR; 1H-, 13C-, 19F-, 31P-NMR; MS). A weak, but significant Ni Si interaction through the cage is indicated by the following results: (i) Large low-field shifts δδF of 35.2 ppm (12), 38.3 ppm (18) and 37.7 ppm (19); (ii) 6J(PF) coupling constants [or 3J(PNiSiF) through the cage] of 6.0 Hz (12) and 7.6 Hz (18) together with a low-field shift δδSi of 12.8 ppm (12); (iii) NiSi distances of 3.95 A in 7 and 3.92 A in 12, accompanied by a compression of the cage along the Ni ··· Si axis. An additional release from the high charge density on Ni results from π-backbonding to the phosphane ligands.

Alternativ‐Liganden. XXXII [1]. Neue Tetraphosphan‐Nickelkomplexe mit Tripod‐Liganden des Typs XM′ (OCH2PMe2)n(CH2CH2PR2)3 – n (M′ = Si, Ge; n = 0 – 3)

Purple acid phosphatases (PAPs) hydrolyzing activated phosphoric acid esters and anhydrides have in common a two-metal center with a tyrosine-Fe(III) charge transfer transition responsible for the color. In the mammalian enzymes from the spleen, macrophages, osteoclasts, and uterine fluids, the second metal in the active site is Fe(II); whereas, the plant enzyme kidney bean PAP (kbPAP) has an Fe(III)–Zn(II) active center. The structure of the homodimeric 111-kDa kbPAP shows the active site at the carboxy end of two sandwiched β–α–β–α–β motifs. The two metal ions are bridged monodentately by Asp164. The iron is further coordinated by Tyr167, His325, and Asp135, and the zinc by His286, His323, and Asn201. The active-site structure is consistent with proposals on the mechanism of phosphate ester hydrolysis by nucleophilic attack on the phosphate by an Fe(III)-coordinated hydroxide ion. Protein isolation, biological functions, sequences, activity, comparison of mammalian and plant PAPs, and the functional aspects of both types are discussed extensively.


3D Structure



Keywords:

purple acid phosphatase;
tartrate-resistant acid phosphatase;
uteroferrin;
iron protein;
zinc protein;
X-ray structure

Bernt Krebs

Papers

Synthese und Struktur von [Fe(SPh)2(NO)2]- dem „Monomeren“ des Roussinschen Phenylesters/ Synthesis and Structure of [Fe(SPh)2(NO)2]- , the “Monomer” of Roussin’s Phenyl Ester

Ein Beitrag zu den Koordinationsverhältnissen in den gasförmigen MAI2Cl8‐Komplexen Das Spektrum von CoAl2ClnI8–n und die Kristallstruktur von PdAl2Cl8

Formation of Large Clusters in the Reaction of Lanthanide Cations with Heptamolybdate

Alternativ‐Liganden. XXXII [1]. Neue Tetraphosphan‐Nickelkomplexe mit Tripod‐Liganden des Typs XM′ (OCH2PMe2)n(CH2CH2PR2)3 – n (M′ = Si, Ge; n = 0 – 3)

Purple Acid Phosphatase