bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metallkomplexe funktioneller Isocyanide, XIII Bis(oxazolidin-2-yliden)-Komplexe von Mangan(I) und Nickel(II) / Metal Complexes of Functional Isocyanides, XIII Bis(oxazolidin-2-ylidene) Complexes of Manganese(I) and Nickel(II)
Authors: Fehlhammer Wolf Peter , Plaia Ulrike 
Published: March 2015

Abstract
The dicarbene complexes, MnBr(CO)3 [xxx] (1) and [xxx] (2), are synthesized from metal carbonyl precursors and CNCH2CH2OH . Factors influencing this 2-hydroxyalkyl isocyanide → N ,O-carbene isomerization are discussed. The crystal and molecular structure of 2 shows a distorted trigonal geometry about the central Ni atom. Extensive hydrogen bonding ((N )H ··· F 2.09, 2.38 Å ) occurs between cations and anions giving rise to infinite chains. Other pertinent bonding parameters are Ni-C (carbene) 1.860(4), 1.864(4) Å; C(carbene) [xxx] N 1.309(6), 1.304(6) Å , and C - Ni - C 97.7(2)°.
Große Übergangsmetallcluster, IV Ru55-, Rh55- und Pt55-Cluster / Large Transition Metal Clusters, IV Ru55-, Rh55- and Pt55-Clusters
Authors: Schmid Günter , Huster Wilfried 
Published: March 2015

Abstract
The novel cluster compounds Ru55[P (tert -Bu)3]12Cl20, Rh55(PPh3)12Cl6 and Pt55[As(tert -Bu)3]12Cl20 have been prepared by the reaction of (RuCl3/P (tert-Bu)3), (Ph3P)3RhCl and trans-[As(tert -Bu)3]2PtCl2, respectively, with B2H6 in THF or benzene. Diborane reduces the metal salts and serves to capture excess of phosphine or arsine ligands. Molecular weight determinations prove the cluster size. High resolution transmission electron microscopic investigations on the Pt55 cluster show the expected full-shell cuboctahedron with 55 closest-packed platinum atoms. 31P NMR spectra prove the ligands to be very mobile.
Uber die drei discotischen Mesophasen der scyllo-Inosithexaester / On the Three Discotic Mesophases of scyllo-Inositol Hexaesters
Authors: Kohne Bernd , Praefcke Klaus , Billard Jan 
Published: March 2015

Abstract
The mesophases of eleven homologous hexaesters ( 1b -1) of the naturally occurring scylloinositol (1a ) representing the first series of alicyclic saturated discogens are studied by calorimetry and optical microscopy. The three derivatives 1 b -d of this hexahydroxy cyclohexane with each six acetyl, propionyl or butyroyl side chains, respectively, exhibit a very organized discophase D1. The hexa-0-acetyl-scyllo-inositol (1b , range of mesophase: Δt = 4.8 °C!) is the discogen having the shortest identical ester groups as lateral functions so far reported for discotic liquid crystals. The pentanoyloxy com pound (1e) exhibits a monotopic D0 mesophase and an enantiotropic optically isotropic and, probably, cubic mesophase D0 different from the smectic D mesophase.
Versus increasing temperature the phase sequences are D1 → DE and D1 → D0. Examples of mutual orientation of D1 and DE discophases and binary mixtures exhibiting stable DE discophase at room temperature are also reported. The mesophases of seven more compounds (1f-1) of the homologous series having lateral functions larger than pentanoyloxy are identified by total miscibility as discophase DE. Their stable temperature ranges are very wide e.g. hexa-0-heptanoyl-scyllo- inositol (1g , Δt = 132 °C) which are exceeded only by those discogens having much larger “cores” (up to now of aromatic character only).
Untersuchungen zur möglichen Existenz des S4N4
⊕-Radikalkations und die Kristallstruktur von S4N4[FeCl4] / Investigations Concerning the Possible Existence of the S4N4
⊕ Radical Cation and the Crystal Structure of S4N4H[FeCl4]
Authors: Thewalt Ulf , Holl Konrad , Demant Udo , Müller Ulrich , Dehnicke Kurt 
Published: March 2015

Abstract
Brom ination o f S4N 4 Cl[FeCl4], Preparation o f S4N 4 H [FeX 4] (X = Cl, Br), IR Spectra, Crystal Structure of S4N4H[FeCI4] S4N 4 H [FeC l4] as well as S4N 4 D [F eC l4] were prepared in C H 2C12 by reaction o f S4N 4 with FeC l3 and C H 3C O O H and CH 3C O O D , respectively. Bromination o f S4N 4C l[FeCl4] with M e3SiBr in C H 2 C12 yields S4N 4 H[FeBr4]; in this reaction, S4N 4 Br® is presumably formed initially; it then decom p oses by elimination o f bromine and formation of the S4N 4® radical cation; the latter reacts with the solvent, yielding the S4N 4 H® cation. Brom ination of S3N 2C l[FeCl4] with M e3SiBr affords S6N 4 [FeBr4]2. The IR spectra o f the com pounds are discussed. The crystal structure o f S4N 4 H [FeC l4] was determined by X-ray diffraction (1210 observed reflexions, R = 0.035). Crystal data: a = 803.8, b — 1003.9, c = 1507.7 pm, β = 104.52°, Z = 4, space group P 2,/c.
Characterisation of Metal Binding Sites for 8-Azaguanine and 8-Azahypoxanthine Derivatives Synthesis and X-Ray Structural Analysis of Methylmercury(II) and Zinc(II) Complexes
Authors: Sheldrick W. S. , Bell P. 
Published: March 2015

Abstract
The complexes [(CH3Hg)AGuaH ] (1) and [(CH3Hg)2AGua] • H2O (2) have been isolated from aqueous 1:1 and 2:1 solutions of CH3HgOH and 8 -azaguanine (AGuaH2) at respective pH values of 5 and 9. Only one CH3Hg+ complex of 8 -azahypoxanthine (AHxH2), namely [(CH3Hg)2AHx] (3), could be isolated under analogous conditions. X-ray structural analyses established N1 and N9 as metal binding sites in 3 and N9 as the coordination position in [Zn(H2O)4(AHxH)2] (4). With 8-aza-9-benzylhypoxanthine (9-BzAHxH) only one CH3Hg+ complex [(CH3Hg)9-BzAHx] (5) could be isolated in the pH range 2-10. N1 was established by X-ray structural analysis as the binding site. The relevance o f these findings to an understanding of ligand behaviour of the antineoplastic agent 8 -azaguanine is discussed.
Reaktionen von Tetrapropyldibismutan mit Chalkogenen und Tetramethyldistiban / Reactions of Tetrapropyldibism uthane with Chalcogens and Tetramethyldistibane
Authors: Breunig Hans Joachim , Müller Ditmar 
Published: March 2015

Abstract
Bis(dipropylbismuth)oxide, -sulfide, -selenide and -telluride are obtained by reactions of tetra­ propyldibismuthane with elem entaloxygen, sulfur, selenium or tellurium. Tetramethyldistibane and tetrapropyldibismuthane undergo an exchange reaction to give (dipropylbismuthino)-dimethylstibane.
Discarin-I, ein neues Peptidalkaloid aus Discaria febrifuga Martius / Discarine-I, a New Peptide Alkaloid from Discaria febrifuga Martius
Authors: Hennig Peter , Morel Ademir , Voelter Wolfgang 
Published: March 2015

Abstract
Besides the already reported alkaloids [1-5] from the root bark extract of Discaria febrifuga Martius, two further peptide alkaloids, the known discarine-B and discarine-I are isolated and their structures elucidated. Discarine-I is a fourteen-m em bered ring peptide alkaloid and the ring is constituted by p-hydroxy styrylamine, β-hydroxyleucine, N-methylisoleucine and tryptophan
Reaktionen N-silylierter Endiamine, I Übergangsmetallkomplexe von 1,3-Diaza-2-sila-4-cyclopentenen / Reactions of N-Silated Endiamines, I Transition Metal Complexes of 1,3-Diaza-2-sila-4-cyclopentenes
Authors: Zettlitzer Michael , Dieck Heindirk tom , Stamp Lutz 
Published: March 2015

Abstract
1,3-Di̲aza-2-s̱ila-4-c̱yclopentenes 1 (DISC), which are electron-rich and easily oxidizable ole­ fins, form strongly coloured, but poorly soluble 1:1 adducts with cuprous halides, while silver trifluoromethylsulfonate oxidizes 1. Much more soluble and again strongly coloured complexes of stoichiometry LPdX2, (L)1.5PdX2 and L 2PdX2 are formed from 1 and palladium halides. The well-crystallizing adduct (PdCl2 · L)2 3a was chosen for an X-ray structure analysis (monoclinic, space group P2/c; a = 10.215(3), b = 14.681(3), c =23.642(5) Å , β = 101.31(2)°; Z = 8 ; R = 0.054), which revealed an almost planar DISC ligand in an oblique η2(C=C)-coordination relative to the π-plane. Structural data and rather peculiar spectroscopic properties encourage a comparison of 3a with complexes, in which an electron-rich olefin is split to give a bis(carbene) ligand system. The electronic reasons for the splitting of electron-rich olefins at d8 metals are discussed under symmetry considerations.
Formation of Triradical Trications from Hexaquaternary Salts Derived from 4,4'-Bipyridine
Authors: McGeachie Joanne , Summers Lindsay A . 
Published: March 2015

Abstract
The syntheses of the hexaquaternary salts 1,1'-bis-[2-(1′-methyl-[4,4'-bipyridinium]-1-yl)-ethyl]-4,4'-bipyridinium hexaperchlorate and 1,1'-bis-[3-(1'-methyl-[4,4'-bipyridinium]-1-yl)-propyl]-4,4'-bipyridinium hexaperchlorate are reported. The salts are reduced in aqueous solution to triradical trications at a potential (E0) of -0.24 V.
Ring-Ketten-Isomerie substituierter Tetrahydropyridinderivate / Ring Chain Isomerism of Substituted Tetrahydropyridines
Authors: Möhrle Hans , Dwuletzki Heinz 
Published: March 2015

Abstract
The reactions of δ-bromoketones 1 with amines lead to cyclic enamines 6 or secondary δ-am inoketones 3 depending on the nature of the amine used. Amino substituents which increase the nucleophilicity forces the course of the reaction towards cyclisation to 6 , which in turn yields the corresponding iminium salts 5. This pathway can be suppressed by large substituents leading to the formation of ammonium salts 4.
Synthesis and Crystal Structure of CuC4O4·2 H2O
Authors: Robl Christian , Weiss Armin 
Published: March 2015

Abstract
The monoclinic compound CuC4O4·2 H2O (space group P 21/c) was prepared from aqueous acetate buffered solution. The structure was solved from a twinned crystal. Chains consisting of squarate dianions and Cu2+ , which is coordinated octahedrally in a strongly distorted manner, are the main feature. Only two squarate oxygen atoms contribute considerably to the coordination of Cu2+. Neighbouring chains share common oxygen atoms (H2O . Osquarate) of the coordination polyhedra. Furthermore the chains are very probably interlinked by strong hydrogen bonds. Thermal decomposition of CuC4O4·2 H2O leads to CuO.
A TTF Derivative Acting as a Chelate Ligand: Structure of μ-[Tetra(methylthio)tetrathiafulvalene]di[diodoniercury(II)], (TTM-TTF) (HgI2)2, and the Structure of a Second Modification of Free TTM-TTF
Authors: Endres Helmut 
Published: March 2015

Abstract
(TTM -TTF)(HgI2)2 [TTM -TTF = tetra(methylthio)tetrathiafulvalene, C10H12S8] was obtained as one of the products of the reaction of TTM -TTF with HgI2 . It is triclinic, P 1̄ , a = 7.667(1), b = 8.308(2), c = 11.608(3) Å , α = 81.42(2), β = 75.15(2), γ = 67.06(2)°, V = 657.2 Å3, Z = 1, Mr = 1297.53, dc = 3.28 g cm-3, final RK = 0.035 for 2755 reflections and 116 parameters. The donor acts as a bridging chelate ligand by coordination of the S atoms of the -SCH , groups to Hg, with Hg -S distances of 3.038(2) and 3.157(3) Å . Hg···I contacts of 3.648(1) and 3.761(1) Å lead to coordination-polymer like chains of the Hg complexes. TTM -TTF (phase II) is triclinic, P 1̄, a = 5.141(2). b = 7.565(3), c = 10.950(2) Å , α = 72.46(2), β = 79.03(2), γ = 84.87(3)°, V = 398.4 Å3, Z = 1, Mr = 388.73, dc = 1.62 g cm-3, final Rw = 0.032 for 1876 reflections and 106 parameters. The molecules form sheets of stacks with shorter interstack S···S contacts [3.591(1) Å] than within the same stack [3.720(1) Å].
Synthese und Kristallstruktur von Bis[1,5-ditolylpentaazadienido-thallium(I)] und Bis[1,3-diphenyltriazenido-thallium(I)]/Synthesis and Crystal Structure of Bis[1,5-Ditolylpentaazadienido-thallium(I)] and Bis[ 1,3-diphenyltriazenido-thallium(I)]
Authors: Beck Johannes , Strähle Joachim 
Published: March 2015

Abstract
The reaction of TlNO3 with 1,5-ditolylpentaazadiene in aqueous ammonia yields red [Tl(TolNNNNNTol)]2, which crystallizes in the monoclinic space group C2/c with the lattice constants a = 3322.9, b = 847.6, c = 1107.9 pm, β = 105.93°, Z = 4. The structure consists of dimeric molecules, in which two separate pentaazadienido chains and two T1 atom s are so arranged as to form trigonal pyramids, TlN3, with an average Tl-N distance of 274 pm. The N -N distances in the N5 chain are equal within the standard deviations, indicating a high ionic character for the Tl -N bonds. Intermolecular interactions link the dimers into infinite chains. Each Tl atom , already coordinated by three nitrogen atoms, is additionally coordinated by two nitrogen atoms of one neighbouring complex and the aromatic tolyl ring of another ligand. The distance between Tl and the π-bonded tolyl ring is 333 pm, comparable with values of other Tl arene complexes.
The reaction of TlNO3 with 1,3-diphenyltriazene in the presence of NaOH yields red [Tl(PhNNNPh)]2, which crystallizes in the monoclinic space group P21/n with the lattice constants a = 1040.6, b = 636.7, c = 1763.5 pm, β = 96.98°, Z = 2. The structure consists of centrosymmetric dimeric molecules. The 1,3-diphenyltriazenide anion acts as an unsymmetrical bidentate chelating ligand for each Tl atom. The Tl-N distances (Tl-N1 = 261, Tl -N3 = 277 pm) are significantly different. N1 is additionally bonded to the Tl atom of the neighbouring monomer. The dimeric complexes form a planar, four-membered Tl2N2 ring in the form of a slightly distorted square. π-Interactions between Tl and a phenyl ring of a neighbouring complex link the dimers to form infinite chains with a Tl-phenyl distance of 327 pm.
Bonding in the BaPdSn3 Structure
Authors: Li Jing , Hoffmann Roald 
Published: March 2015

Abstract
The body-centered BaPdSn3 structure contains Sn atoms in tetrahedral and square-pyramidal five-coordinate sites, and Pd in square-pyramidal environm ents. The PdSn3
2- three-dimensional lattice can be formally decomposed into first two-dimensional layers, then into a square Sn lattice with capping Sn and Pd atoms. This geometrical decomposition also serves as a construction principle for building up the electronic structure of this material. Many similarities to BaAl4 emerge. There is electron deficient multicenter bonding in the layer, normal two-center bonding Sn-Pd between layers. Pd 4d orbitals do not contribute significantly to the bonding.
Molecular Complexes, 8 Formation Constants and Topology of Complexes of Tetramethyluric Acid. An 1H NMR Reinvestigation Based on the AUS Concept and on the Shift Difference Method. A Revised Complex Topology
Authors: Jäckel Hannelore , Stamm Helmut 
Published: March 2015

Abstract
The complexation of tetramethyluric acid (TMU) with the donors (D) benzene (B), biphenyl (BP), naphthalene (N), and phenanthrene (P) in CCl4 is investigated by 1H NMR shift measure­ments relative to an external reference in a series of solutions containing a constant concentration of TMU and varying concentrations of D under conditions of a great excess of D. Reduction of data according to the AUS concept (additional nonspecific shielding) provided formation con­stants K (in 1/mol) and Icpt/K as approximations of the complex shifts. The increase in K from .17 (TMU-B) to .75 (TMU-N) to 2.08 (TMU -P) is compatible with a face-to-face complexation and with a preferred contact between the donor and TMU along the area of positive charge in the TMU molecule. The estimated Icpt/K figures indicate the centers of the complexes to lie between N-3 and N-9 of TMU, quite in the center of the positive charge area of TMU. K and Icpt/K figures for TMU-BP indicate this complex to have the same topology as TMU-B. the second ring of BP rotating in plane around the complexing ring of BP. The previous rejection of a face-to-face topology for such complexes was based on a misinterpretation of the ring current calculations. Deviating complex parameters in the previous report are shown to be caused by a solvent effect (CDCl3) and in part by methodical errors.
Differences between the Reaction of 2-Benzylidenecyclopentanone with Malononitrile and the Reaction of Cyclopentylidenemalononitrile with Aromatic Aldehydes; Synthesis of Strong Fluorescent o-Aminonitriles
Authors: Mirek Julian , Milart Piotr 
Published: March 2015

Abstract
It was found that instead of the Knoevenagel condensation of cyclopentylidenemalononitrile with aromatic aldehydes, a complex reaction takes place leading to 5,7-dicyano-1-arylidene-4-arylindanes. The same compounds were formed in the reaction of the cyclopentylidenemalono­nitrile dimer with aldehydes. It is suggested that the cyclopentylidenem alononitrile dimers un­dergo an electrocyclic ring opening leading to conjugated triene systems. These species are very reactive intermediates and may react with aldehydes in the next step. Bulky substituents in 2,5-dibenzylidenecyclopentanone hindered its Knoevenagel condensation with malononitrile but did not hinder its Michael addition leading to a 4H -pyrane derivative. Solutions of the obtained o-aminonitriles exhibit strong fluorescence in a variety of solvents.
The Crystal Structure of TeCl3
+ AuCl4
-
Authors: Jones Peter G. , Jentsch Dieter , Schwarzmann Einhard 
Published: March 2015

Abstract
TeCl3
+ AuO4
- crystallizes in the triclinic space group P1̄ with a = 7.564(2), b = 7.720(3), c = 8.964(3) Å , α = 78.26(3), β = 88.84(3), γ = 89.35(3)°, Z = 2. The structure was refined to R 0.041 for 1380 reflections. The cation polyhedron, including secondary Te···Cl interactions, is a square pyramid with mean Te -Cl 2.294, Te···Cl 3.028 Å. The secondary interactions link the ions to form centrosymmetric (TeCl3·AuCl4)2 dimers.
Polymerie 2,5-Dihydroxy-1,4-benzoquinone Transition Metal Complexes Na2(H2O)24[M2(C6H2O4)3] (M = Mn2+, Cd2+)
Authors: Weiss Armin , Riegler Eugen , Robl Christian 
Published: March 2015

Abstract
The isotypic compounds Na2(H2O)24[M2(C6H2O4)3] (M = Mn2+, Cd2+) form infinite net-like layers. The transition metal ion is coordinated octahedrally. The dianion of 2,5-dihydroxy-1.4- benzoquinone, consisting of two allyl systems interlinked by two long C-C distances (152-153 pm), acts as a chelating ligand. Adjacent layers are connected by hydrogen bonds. The stacking sequence of these layers, ···AAA···, leads to channels, which are filled by hydrated Na+ ions. The Na+ ions are coordinated in a distorted octahedral fashion, with neighbouring octahedra sharing common faces.
On the Autoxidation of Aqueous Sodium Polysulfide [1]
Authors: Steudel Ralf , Holdt Gabriele , Nagorka Regine 
Published: March 2015

Abstract
Aqueous sodium polysulfide of composition in the range Na2S2.0 to Na2S4.6 undergoes autoxidation by either air or pure oxygen at temperatures of between 23 and 40 °C according to the equation
[xxx]
Iodometric determination, vibrational spectra and ion-pair chromatography showed that neither sulfate, sulfite nor polythionates are formed and that the sulfur precipitated consists of S8 (≥ 99%).
Metallorganische Verbindungen für MOCVD-Prozesse: Kristallstruktur des dimeren Addukts [Et3AsXAsCl3]2 / Crystal Structure of the Dimeric Triethylarsine-Arsenictrichloride Adduct, Dimer [Et3AsxAsCl3: Synthesis, Molecular and Crystal Structure
Authors: Baum Gerhard , Greiling Arnd , Massa Werner , Hui Benjamin C. , Lorberth Jörg 
Published: March 2015

Reaction of Et3As with AsCl3 in n-pentane yields dimeric [Et3AsxAsCl3]2 in quantitative yield; sublimation in vacuo affords white crystals.
X-Ray diffraction data were collected at 133 K (3149 independent observed reflections; R = 0.029. Rw = 0.026). Crystal data: monoclinic space group P21/c, a = 761.9(8). b = 1118.8(4). c = 1406.0(14) pm; β = 100.90(4)°. Ζ = 2 dimers.
The dimer contains a planar As2Cl6-unit with terminal and bridging As-Cl bonds; each arsenic atom is bonded to a Et3As molecule via an arsenic-arsenic bond. The dimer thus has pseudo four- and six-coordinate arsenic atoms.
Solid State Structure of 2,2,4,4,6,6-Hexa(β-naphthyloxo)cyclophosphazatriene and Dipole Moments of Hexa(aryloxo)cyclophosphazatrienes
Authors: Bandoli Giuliano , Casellato Umberto , Gleria Mario , Grassi Antonio , Montoneri Enzo , Pappalardo Giuseppe C. 
Published: March 2015

The crystal and molecular structure of [NP(OC10H7)2]3 was determined by X-ray analysis.
The dipole moments of this compound and of the hexa(phenoxo)cyclotriphosphazatrienes of formula [NP(OC6H3XX′Y)2]3 (X = X′ = H, Y = p-Br; X = m-CH3,. X′ = H. Y = p-Cl; X = X′ = m-CH3, Y = p-Cl; X = X′ = m-CH3, Y = H; X = X′ = H, Y = p-CH(CH3)2; X = X′ = H, Y = p-C(CH3)3) were measured in benzene at 25°C. Crystals of [NP(OC10H7)2]3 are monoclinic with unit cell dimensions a = 24.870(15), b = 7.712(8), c = 27.687(14) Å, β = 115.85(7)°; space group P21/c. The structure was refined to an agreement factor of 0.09. The phosphazene ring deviates (max. deviation 17°) from planarity. and mean distances (A) and angles (°) are P-N 1.58(1). P-O 1.58(1), O-C 1.41(2); P-N-P 120(1), N-P-N 119(1), P-O-C 124(2). The conformations of the naphthyloxo groups at P(2) and P(3) are similar, and different from the group at P(1).
Dipole moment analysis showed that the solid state conformation changes in the solution state. The measured value was in agreement with a symmetric conformation in which at the O-P-O plane each naphthyloxo group is rotated by ca. 40-50° from the anti-coplanar arrangement relative to this plane. The dipole moment data for the p-substituted phenoxo derivatives agree with such a conformation, but the analysis of the dipole moment values of phosphazenes having phenoxo groups bearing more than one substituent group and p-CH(CH3)2 substituent failed to do so due to the inherent limitations of the method.
Untersuchungen an Polypseudohalogeniden, VI / Studies on the Polypseudohalides, VI
Authors: Tebbe Karl-Friedrich , Krauß Norbert 
Published: March 2015

The new compound Na[I(CN)2] · 2 H2O can be prepared by addition of iodine to a concentrated aqueous solution of sodium cyanide. It crystallizes in the monoclinic space group P21/c with a = 1044.0(2), b = 480.2(2), c = 730.2(2) pm, β = 95.94(2)° and Z = 2. The crystal structure has been refined to Rf = 0.027 for 692 reflections.
The structure may be described as a layer-like package of cations Na+, water molecules and trihalide-analogous anions [I(CN)2]-. The anion is strictly linear at the I atom and nearly linear at the C atoms with φ(I-C-N) = 176.2° and d(I-C) = 231.1, d(C-N) = 110.6 pm. The cation is surrounded by a slightly distorted octahedron of nitrogen and oxygen atoms with d(Na · · ·N) = 263.8, d(Na · · · O) = 242.0, 242.8 pm
Anodische Oberflächen- und Volumenoxidation graphitischer Materialien in neutralen und alkalischen wäßrigen Lösungen / Anodic Surface and Bulk Oxidation of Graphitic Materials in Neutral and Basic Aqueous Solutions
Authors: Besenhard J. O. , Jakob J. , Krebber U. , Möller P. , Sauter R. F. , Kurtze A. , Kanani N. , Meyer H. , Hörber J. K. H. , Jannakoudakis A. D. 
Published: March 2015

Anodic oxidation of graphitic materials in aqueous electrolytes is a complex process which may yield e.g. higher stage intercalation compounds and lamellar graphite oxides, acidic surface or defect oxides and gaseous or colloidal decomposition products. Kind and concentration of the electrolyte solution are the most important parameters to control this wide-spread distribution of products. Based on electrochemical and microscopic studies on HOPG and carbon fibres, a mechanistic concept of electrolyte effects is proposed:
In dilute aqueous solutions, attack of OH• radicals formed in the primary electrochemical step is the dominant reaction pathway leading to formation of covalent carbon-oxygen bonds. Due to their reactivity, OH• radicals are able to attack basal plane carbon sites and also to create 3-dimensional defect oxides. Dissociation or capture of OH• radicals - which is favoured in basic and in most concentrated neutral solutions, respectively, - results in less active radical species and limits the attack to thermodynamically less stable carbon atoms at edge sites which may be either oxidized or removed. Due to acidification of the diffusion layer of anodes even in neutral aqueous electrolytes, direct current oxidation always yields higher stage acid intercalation compounds and lamellar graphite oxide as by-products. This can be almost prevented by alternating current oxidation.