bluuebunny/crossref_metadata_2025 huggingface dataset:
Speciation of Selenium(IV) and Selenium(VI) using Coupled Ion Chromatography—Hydride Generation Atomic Absorption Spectrometry
Authors: Goldberg Sabine , Martens D. A. , Forster H. S. , Herbel M. J.
Published: December 2005

A simple method was developed to speciate inorganic Se in the μg L−1 range using coupled ion chromatography‐hydride generation atomic absorption spectrometry. Because of the differences in toxicity and adsorption behavior, determination of the redox states selenite, Se(IV), and selenate, Se(VI), is important. We used anion exchange chromatography to separate Se(IV) and Se(VI) based on differences in retention times. Samples were then mixed with concentrated HCl and passed through a 130°C sand bath to reduce Se(VI) to Se(IV) for Se determination as the hydride. Detection limits were 0.68 μg L−1 for Se(IV) and 0.55 μg L−1 for Se(VI). Spiking of actual sample solutions with Se(IV) and Se(VI) showed the procedure to be accurate for solutions with Se(IV)/Se(VI) ratios ranging from 1:4 to 4:1. Average recovery was 93.1% for Se(IV) and 108% for Se(VI). The technique was used to determine Se(IV) and Se(VI) in deionized water and actual and synthetic irrigation waters.
Synthesis and Characterization of a New [4.0.4.0] Porphyrin-like
Antiaromatic Macrocycle
Authors: JOHNSON MARTIN R. , SLEBODNICK CARLA , IBERS JAMES A.
Published: December 2005

The antiaromatic macrocycle 2 has been prepared by the reaction of the
bipyrrole dialdehyde 1 with hydrazine. In the crystal structure of 2· DMSO
molecule 2 is nearly planar, the mean deviation of the 28 atoms of the core
from the best least-squares plane being 0.227 Å. AM1 geometric optimization
of the core of 2 leads to a fully planar macrocycle. Attempts to oxidize 2
to 3 were largely unsuccessful, yielding only limited evidence for the
formation of 3. The antiaromatic precursor 2 turns out to be much more
stable than the putative aromatic product 3. Molecular orbital calculations
at the AM1/PM3 level indicate the S 0- T
1 gap for 3 is only about 0.2 eV and hence is
readily accessible via intersystem crossing from any visible transition.
This small band gap of 3 contrasts starkly with the much larger S
0- T 1 band gap of 1.86 eV
calculated for 2 itself. Paratropicity in antiaromatic systems is usually
attributed to a low-lying paramagnetic state, with band gaps ranging up to
2.1 eV. For the 2/3 system the S 0- T
1 band gap is substantially larger for the
paratropic species than for the putative diatropic species.
Tetrathia Macrocycle-bridged Dimeric with Hexakis (alkylthio) Substituents and Network Polymer Phthalocyanines
Authors: GÜREK A. G. , BEKARO ĞLU Ö.
Published: December 2005

1,4,7,10-Tetrathia (12-crown-4)-bridged new polymeric phthalocyanines 9 and 10 have been synthesized by the reaction of tetracyanodibenzo[1,4,7,10-tetrathia (12-crown-4)] in the presence of a strong organic base or Zn ( OAc )2 respectively. Furthermore, 1,4,7,10-tetrathia (12-crown-4)-linked peripherally octa-substituted dimeric phthalocyanine 12, which contains a combination of hexakis(alkylthia) side chains was synthesized by the reaction of subphthalocyanine 11 with the iminoisoindoline derivative 8. The new compounds have been characterized by elemental analyses, IR, UV/vis, mass, 1 H NMR and 13 C NMR spectroscopy. The thermal stabilities of the compounds were determined by thermogravimetric analysis. The electrical conductivity of the polymeric, 9 and 10, and dimeric phthalocyanines, 12 and 13, are in the semiconductor range; chemical doping with NOBF 4 increases the d.c. conductivity of 10 by a factor of four.
Cobalt(III) Porphyrin-catalysed Hydride Reduction of 10-Methylacridinium ion and Hydrometallation of Alkenes and Alkynes by Tributyltin Hydride
Authors: FUKUZUMI SHUNICHI , NOURA SOUTA
Published: December 2005

Cobalt(III) tetraphenylporphyrin catalyses a hydride transfer reaction from tributyltin hydride to 10-methylacridinium ion via the formation of hydridocobalt(III) tetraphenylporphyrin, which is the rate-determining step, followed by facile hydride transfer from the hydridocobalt(III) porphyrin to 10-methylacridinium ion in acetonitrile. Tributyltin hydride is also effective for the hydrometallation of alkenes and alkynes with cobalt(III) tetraphenylporphyrin to yield the corresponding organocobalt(III) porphyrins regioselectively. The hydrometallation is suggested to proceed via the hydride transfer from tributyltin hydride to cobalt(III) tetraphenylporphyrin to give the hydridocobalt(III) porphyrin, followed by the hydrogen transfer from hydridocobalt(III) porphyrin to alkenes and alkynes to yield the corresponding organocobalt(III) porphyrins. The regioselectivities are consistent with the stabilities of radicals generated by the hydrogen transfer from hydridocobalt(III) porphyrin to alkenes and alkynes. The rates of the electrophilic cleavage of cobalt-carbon bonds of organocobalt(III) porphyrins by trifluoroacetic acid in MeCN are also reported.
The Synthesis of Isomeric Dithymidyl-phosphorus(V)-meso-tetraphenylporphyrins
Authors: GOH GERARD KIAN-MENG , CZUCHAJOWSKI LESZEK
Published: December 2005

The synthesis of three novel axial dinucleosides was successfully accomplished. The compounds are 5″- O , 5″- O -dithymidylphosphorus(V)-meso-tetraphenylporphyrin, 5″- O , 3″- O -dithymi-dylphosphorus(V)-meso-tetraphenylporphyrin, and 3″- O , 3″- O -dithymidylphosphorus(V)tetraphenylporo-phyrin. These compounds could provide a lead toward the synthesis of an oligo-porphyrinyl DNA analogue that represents a system containing phosphorus(V)porphine units axially connected through the 5″- O -thymidine-3″- O bridges.
Electrochemical CO2 Reduction Catalysed by Cobalt Octacyanophthalocyanine and its Mechanism
Authors: ABE TOSHIYUKI , IMAYA HIROSHI , YOSHIDA TSUKASA , TOKITA SUMIO , SCHLETTWEIN DERCK , WÖHRLE DIETER , KANEKO MASAO
Published: December 2005

Electrochemical CO 2 reduction was studied by using a graphite electrode coated with cobalt octacyanophthalocyanine ( CoPc ( CN )8) and dipped in an aqueous phase. The most active and selective CO 2 reduction was achieved at −1.20 V (vs Ag / AgCl ) with the ratio of the produced CO / H 2 around 10 at pH 9.3. The electrocatalytic CO 2 reduction by CoPc ( CN )8 could be achieved at a more positive applied potential than non-substituted CoPc ( CoPc ), which can be ascribed to the relatively positive redox potential of CoPc ( CN )8. The catalytic mechanism of the CoPc ( CN )8 in a homogeneous system was investigated by an in situ potential-step chronoamperospectroscopy under argon and under CO 2 as well. In CoPc ( CN )8 the rate-determining step was an intermediate formation step, while in CoPc it was the second reduction of the complex.
Cobalt Octaethyltetrapyrazinoporphyrazine: Spectroscopy, and Electrocatalytic and Kinetic Study of Dioxygen Reduction at a Glassy Carbon Electrode
Authors: DONG SHAOJUN , LIU BAIFENG , LIU JUNLI , KOBAYASHI NAGAO
Published: December 2005

Cobalt octaethyltetrapyrazinoporphyrazine was synthesized and characterized by electronic absorption and magnetic circular dichroism spectroscopy. These spectroscopies and molecular orbital calculations within the framework of the Pariser–Parr–Pople approximation revealed that the effective π-conjugation system of octaethyltetrapyrazinoporphyrazine is smaller than phthalocyanines. For the first time, the electrochemical behaviour of cobalt octaethyltetrapyrazinoporphyrazine irreversibly adsorbed onto a glassy carbon electrode as a surface modifier is reported. The cobalt derivative/glassy carbon electrode showed catalytic activity for oxygen reduction. Surprisingly, the peak potentials for oxygen reduction at this electrode coincide well with those where Co II is reduced to Co I over the whole pH range, indicating that the active species for dioxygen reduction is Co I rather than the Co II species. A possible mechanism for the electrocatalysis of oxygen is discussed.
Synthesis and Characterization of Octakis (hydroxyethylthio)-substituted Phthalocyanines
Authors: BAYIR Z. ALTUNTAŞ , HAMURYUDAN E. , GÜREK A. G. , BEKAROĞLU Ö.
Published: December 2005

The new metal-free phthalocyanine 2 and phthalocyaninatometals 3–5 ( M = Ni , Co and Zn ) carrying eight hydroxyethylmercapto groups on peripheral positions have been synthesized from 1,2-bis(hydroxyethylmercapto)-4,5-dicyanobenzene in the presence of a suitable anhydrous metal salt [ NiCl 2, CoCl 2 or Zn ( O 2 CMe )2] or hydroquinone. Zinc (II) phthalocyaninate reacted with palladium(II) salt to form complexes with a phthalocyanine (metal ratio of 1:4). The electrical conductivity of the phthalocyanines 2, 3, 5, 5a are in the semiconductor range.
Synthesis and Catalytic Capability of Metalloporphyrins Encapsulated in Molecular Sieve Supercages
Authors: WANG XING-QIAO , GAO SHUANG , CAO CHANG-SHENG , YU LIAN-XIANG , GUO JING-FU , CAO XI-ZHANG
Published: December 2005

A stepwise synthesis method was used to encapsulate tetrachloro-tetramethyl porphyrin in NaCoX molecular sieve supercages. Characterization of the encapsulated porphyrin was carried out by UV-vis and IR Spectroscopy, DTA, SEM and EPR. A comparison was made of the activities of tetrachloro-tetramethyl porphyrin, its Co ( II ) complex, NaCoX molecular sieve and the encapsulated porphyrin as catalysts in the oxidation reactions of styrene and p-cresol. The stability and catalytic capability of the metalloporphyrin were increased after combination of the porphyrin with the molecular sieve. In addition, this new type of catalyst, tetrachloro-tetramethyl porphyrin encapsulated in NaCoX molecular sieve supercages, not only possesses the advantages of both the porphyrin and the molecular sieve, but also makes up for their respective deficiencies. In this study, another method called sealing–melting was also used to encapsulate the Zn ( II ) complex of meso-tetraphenyl-tetrabenzoporphyrin into NaY molecular sieve supercages. The catalytic capabilities of the free Zn ( II ) complex of meso-tetraphenyl-tetrabenzoporphyrin, the Zn ( II ) complex encapsulated in NaY molecular sieve supercages and the NaY molecular sieve itself in the oxidation of styrene by hydrogen peroxide were also studied. The experimental results again confirmed that both the stability and catalytic capability of the metalloporphyrin encapsulated in molecular sieve supercages are increased.
Photoexcitation and Electron Transfer Reactions of Zinc Lipidporphyrins in DMSO
Authors: OHGUSHI TAKERU , LI ZI-CHEN , LI FU-MIAN , KOMATSU TERUYUKI , TAKEOKA SHINJI , TSUCHIDA EISHUN
Published: December 2005

The photophysical and photochemical properties of 5,10,15,20-tetrakis{α,α,α,α-o-[2′,2′-dimethyl-20′-((2″-(trimethylammonio)ethyl)phosphonatoxy)alkanamido]phenyl}porphinatozinc(II) (zinc lipidporphyrins, ZnLPs ( C 10, C 18)) have been studied in homogeneous DMSO solution and compared with those of 5,10,15,20-tetrakis{α,α,α,α-o-pivalamidophenyl}porphinatozinc(II) ( ZnTpivPP ) and tetrakis-phenylporphinatozinc(II) ( ZnTPP ). The fluorescence quantum yields of the ZnLPs were lower than that of ZnTPP , but their fluorescence lifetimes were relatively long. The electron transfer reactions from the photoexcited states of these Zn porphyrin complexes to several quinone derivatives were evaluated by fluorescence spectroscopy and laser flash photolysis. The efficiences of oxidative quenching of the excited porphyrins via a dynamic process were significantly decreased by the presence of the bulky substituents on one side of the porphyrin macrocycle. This steric effect of the porphyrin side-chains was quantitatively examined by the Marcus classical treatment.
Synthesis, Reactivity and Structural Chemistry of 5,10,15,20-Tetraalkylporphyrins
Authors: SENGE MATHIAS O. , BISCHOFF INES , NELSON NORA Y. , SMITH KEVIN M.
Published: December 2005

The synthesis, reactivity and full characterization of a series of meso-tetraalkyl porphyrins and metalloporphyrins with R ≡ n-butyl (6), 2-methyl-propyl (7), isopropyl (8), l-ethyl-propyl (10) and tert-butyl (11) groups are reported. Derivatives of the last of these show considerably bathochromically shifted absorption bands and the crystal structure of Zn ( II )11(pyr) exhibits a severely ruffled macrocycle conformation. Systematic crystallographic studies of the porphyrins showed that the free base porphyrins with R ≡ n-butyl ( H 26), 2-methyl-propyl ( H 27) and 1-ethyl-propyl ( H 210) are planar. A larger conformational variety was found for the metal complexes. While most Ni ( II ) derivatives and Pd ( II )8 showed a ruffled macrocycle conformation with a degree of ruffling exceeding that of meso-unsubstituted porphyrins, both planar and non-planar forms were found for the related Cu ( II ) derivatives. The Zn ( II ) complexes of porphyrins with isopropyl or 1-ethyl-propyl exhibited conformations with variable degree of distortion. Together with comparative structures from the literature, this study provides experimental evidence that considerable conformational flexibility exists for meso-alkylporphyrins with substituents less bulky than tert-butyl groups.
AM1 Treatment of Certain Cyclophane-fused Tetraazaporphyrins
Authors: TÜRKER LEMI
Published: December 2005

An AM1-type semiempirical molecular orbital treatment has been performed on certain [22]-type cyclophane-fused tetraazaporphyrins. It has been found that within the isomeric set of structures the most and the least endothermic porphyrins are the ones having non-Hamiltonian and Hamiltonian cyclophane moieties respectively. On the other hand, the lowest HOMO and LUMO and the highest HOMO energies are possessed by the structures bearing Hamiltonian and non-Hamiltonian cyclophane moieties respectively, whereas the highest LUMO energy belongs to a Hamiltonian cyclophane-fused system within the same type of isomeric structures.
On the Mechanism of Dioxygen Electroreduction at Transition Metal meso-Tetrakis Pyridyl Porphyrins—a Comparative Spectroelectrochemical Study
Authors: POPOVICI S. , LEYFFER W. , HOLZE R.
Published: December 2005

The mode of interaction with and the mechanism of the dioxygen reduction reaction at six transition metal α,β,γ,δ-tetra(4-pyridyl)porphyrins (MeTPyPs) deposited on carbon and silver supporting electrodes were investigated with cyclic voltammetry, FTIR and UV-vis spectroscopy and resonance Raman spectroscopy. Results indicate a strong influence of both the ligand and the central metal ion upon the reduction electrocatalysis in terms of electrode overpotentials. Spectroelectrochemical results support a two-electron pathway resulting in hydrogen peroxide as the primary reduction product. A significant influence of the central ion on the vibrational behaviour and the dioxygen reduction mechanism was not found.
Synthesis and properties of soluble phthalocyaninatomanganese(III) complexes
Authors: KNECHT S. , DÜRR K. , SCHMID G. , SUBRAMANIAN L. R. , HANACK M.
Published: December 2005

(Acetato)-1,8,15,22-tetra-n-heptylphthalocyaninatomanganese(III) ( C 7 H 15)4 PcMn -( OAc ) (+structural isomers) (1) and the octa-n-heptyl-substituted (acetato)phthalocyaninatomanganese(III) complexes 1,4,8,11,15,18,22,25-( C 7 H 15)8 PcMn ( OAc ) (2) and 2,3,9,10,16,17,23,24-( C 7 H 15)8 PcMn ( OAc ) (3) have been synthesized and characterized by IR and UV-vis spectroscopy and elemental analysis. Electrochemical investigations of complexes 1 and 2 (CV, SEC) show similar electrochemical behaviour as the literature known compound (chloro)-2,9,16,23-tetra-tert-butylphthalocyaninatomanganese(III) (t- bu )4 PcMnCl (+structural isomers) (4).
Cobalt(II) Porphyrins Supported on Crosslinked Polymer Matrix as Model Compounds
Authors: MATHEW TESSYMOL , KURIAKOSE SUNNY
Published: December 2005

Polymer-bound cobalt(II) porphyrins were studied for their dioxygen—binding capacity. Tetra—aminoporphyrins were anchored on a divinylbenzene (DVB)-crosslinked chloromethyl polystyrene network. The crosslinked, solid polymers were swelled in chloroform and the swollen polymers were used for the entire studies. Ortho-, meta- and para-substituted porphyrin systems were developed by adjusting the bonding position with the help of suitably substituted aminoporphyrins. The products were characterized by chemical and spectroscopic methods. Cobalt(II) complexes of polymeric porphyrins were synthesized and characterized by electronic and ESR spectral methods. The spectra gave evidence for the systematic variation of electronic properties in ortho, meta and para compounds and for the dioxygen-binding capacity of cobalt complexes. These results are discussed.
Synthesis and electrocatalytic properties of octaalkoxycobalt phthalocyanine for the oxidation of 2-mercaptoethanol
Authors: ZAGAL JOSÉ H. , GULPPI Miguel A. , DEPRETZ CHRISTELLE , LELIÈVRE DOMINIQUE
Published: December 2005

We report on the synthesis of cobalt 2,3,9,10,16,17,23,24-octakis(2-ethylhexyloxy)phthalocyanine. This complex, when pre-adsorbed onto graphite electrodes, is active for the electro-oxidation of 2-mercaptoethanol. Its activity is higher than that of cobalt phthalocyanine and cobalt tetrasulfonated phthalocyanine adsorbed on graphite. The voltammetric response of adsorbed cobalt 3,4-octaethylhexyl- oxyphthalocyanine exhibits both Co ( II )/ Co ( I ) and Co ( III )/ Co ( II ) reversible processes. However, the Co ( III )/ Co ( II ) couple shows a pH dependence that is different from that reported for other cobalt phthalocyanine derivatives. The much higher activity of cobalt 3,4-octaethylhexyloxyphthalocyanine compared with cobalt tetrasulfonated phthalocyanine and cobalt phthalocyanine is attributed to the electron-donating ability of the ethylhexyloxy substituents on the periphery of the phthalocyanine ligand.
Syntheses of Octa(dialkylamino)azaphthalocyanines
Authors: MØRKVED EVA H. , KJØSEN HELGE , OSSLETTEN HEGE , ERCHAK NIKOLAI
Published: December 2005

Nickel(II) octa(4-morpholinyl)- (11a) and copper(II) octa(1-pyrrolidinyl)- (11b) azaphthalocyanines have been prepared from the corresponding pyrazine diiminoimides (10). The precursor pyrazine dicarbonitriles (2) gave 6-cyanopyrazine-5-alkyl carboximidates (3-9) as stable intermediates when reacted with ammonia and catalytic amounts of sodium alkoxide in alcohols. Compounds 3-9 were converted to the diiminoimides 10 upon reflux in propanol or butanol for several hours. This unusual reaction pattern was observed for pyrazine-2,3-dicarbonitriles 2 substituted in the 5- and 6-positions with morpholine, thiomorpholine, piperidine or pyrrolidine.
A One-pot, One-step, High-yield Reaction Leading to Metal–Metal Dimacrocycles: the Phthalocyanine Dimer with a Direct Si—Si Linkage
Authors: KOBAYASHI NAGAO , FURUYA FUMIO , YUG GYEONG-CHANG
Published: December 2005

A new concept widely applicable in organometallic chemistry has been introduced for the preparation of cofacial macrocyclic dimers or oligomers. The most notable feature is the use of dimetal or oligometal salts/compounds as templates. In order to exemplify the advantage of this method, a cofacial diphthalocyanine linked by an Si—Si bond has been synthesized in 30% yield in a one-step reaction using hexachlorodisilane as a template and characterized. The cofacial dimer structures are supported by various spectroscopic techniques, including electronic absorption, magnetic circular dichroism, nuclear magnetic resonance and differential pulse voltammetry. However, the unusual phenomenon of a red shift of the main band in the Soret band region was observed.
Axially Polarized NIR Absorption Bands in Electron-deficient Lanthanide Phthalocyanine Dimers and Trimers
Authors: ISHIKAWA NAOTO , KAIZU YOUKOH
Published: December 2005

Absorption and MCD spectra of the two-electron oxidized lutetium phthalocyanine trimer [( Pc ) Lu ( CRPc ) Lu ( Pc )]2+ ( Pc ≡ phthalocyanine ; CRPc ≡ 15- crown -5- substituted Pc ) as well as the MCD spectrum of the oxidized lutetium Pc dimer [ Lu ( Pc )2]+ are reported. These ‘two-electron-deficient’ Pc stacks show absorption bands in the NIR region whose intensities are comparable with those of the Q bands. The band of [ Lu ( Pc )2]+ showed only an MCD B term with no A term contribution, from which we assign the band to a non-degenerate transition whose transition moments are perpendicular to the Pc planes. In both trimer and dimer cases the excitation energy is higher than that of the corresponding NIR band in the ‘one-electron-deficient’ Pc stack [( Pc ) Lu ( CRPc ) Lu ( Pc )]+ or [ Lu ( Pc )2], but the magnitudes of the shift were significantly different (1500 cm−1 in the trimer and 4500 cm−1 in the dimer). The energy shifts are shown to be represented by a pair of two-electron repulsion integrals in a localized orbital basis. The model reproduced well the direction and magnitude of the shifts using numerical values of the integrals.
Rapid Reactions of Phthalocyanines with Tellurium Tetrachloride in Non-aqueous Solutions
Authors: KAGAYA YUTAKA , ISAGO HIROAKI
Published: December 2005

Rapid reactions of tetra(tert-butyl)phthalocyanine, H 2( tbpc ), and its zinc complex, [ Zn ( tbpc )], with tellurium tetrachloride ( TeCl 4) in non-aqueous solutions have been investigated. Upon mixing respective solutions containing the reactants, drastic spectral changes occurred in chloroform and toluene even at room temperature. The electronic spectra of the products indicated that the reactions involved an acid-base equilibrium where the phthalocyanines and tellurium tetrachloride acted as a Lewis base and a Lewis acid respectively. By monitoring the spectral changes based on various initial molar ratios of the reactants, the compositions of the products for each system have been determined. [ Zn ( tbpc )] formed a 1:1 ( tbpc : TeCl 4) adduct in both chloroform and toluene, showing the same spectra close to those of the known monoprotonated phthalocyanines. On the other hand, H 2( tbpc ) formed a 1:1 adduct in chloroform but a 1:3 adduct in toluene even though both products showed essentially the same spectra close to those of the known diprotonated phthalocyanines. Equilibrium constants have been calculated for the four systems. Magnetic circular dichroism (MCD) spectra of conjugated acids of phthalocyanines have been studied for the first time.
Catalysis and Photocatalysis by Phthalocyanines for Technology, Ecology and Medicine
Authors: KALIYA OLEG L. , LUKYANETS EVGENY A. , VOROZHTSOV GEORGY N.
Published: December 2005

This is a review of the recent studies done by the authors in the area of catalysis and photocatalysis by phthalocyanines and related compounds. Several examples of catalytic processes are given. Special attention is paid to the design of new types of photocatalytic systems for photodynamic therapy of cancer and to the development of novel catalytic methods of cancer treatment.
Synthesis of Octasubstituted Cobalt Phthalocyanines and Their Redox Properties
Authors: SAKAMOTO KEIICHI , OHNO-OKUMURA EIKO
Published: December 2005

Octakis(alkoxymethyl) cobalt phthalocyanines with relatively short side chains were synthesized which exhibited no thermotropic liquid crystalline behaviour. The final products as well as the intermediates have been characterized by proton magnetic resonance, infrared and electron spectra and elemental analysis. Cyclic voltammograms were measured for octakis(alkoxymethyl) cobalt phthalocyanines in order to examine their electron transfer properties. The electron transfer properties of octakis (alkoxymethyl) cobalt phthalocyanines depend on the kind and number of substituents and are due to the interaction between the phthalocyanine ring, the central metal which is influenced by the conjugated π electron current of the porphyrazine ring.
Metallurgy, Extractive
Authors: Duby Paul F.
Published: December 2005

Extractive metallurgy that involves chemical production of metals from their naturally occurring compounds, follows mining of the ore, and the processing of the minerals. The essential extractive process, the reduction of a metallic compound to the metal, is often preceded by preparatory steps and followed by a refining one to achieve suitable properties.Pyrometallurgy, processing at high temperature, often yields a molten metal, but may produce a vapor or a solid. Refining is the removal of impurities by volatilization, precipitation, or by transfer into a molten slag phase as in steelmaking. Hydrometallurgy, processing through an aqueous solution, consists of leaching, purification of the pregnant solution, and recovery of the valuable metal by reduction or precipitation of one of its compounds. Electrometallurgy is the use of electrical energy for reducing the metal either from an aqueous electrolyte or from a high temperature melt. Examples are given for all processes.
Minerals Recovery and Processing
Authors: Nagaraj D. R.
Published: December 2005

Minerals recovery from the earth’s crust and the subsequent processing of economic mineral deposits, ie, ores, constitutes a wide variety of steps. Taken together these represent one of the world’s largest industries. Liberation of the value minerals from the ore matrix is a significant undertaking as is the disposal of the gangue materials or tailings once processing is complete. Materials handling is a significant problem in minerals processing as is process or plant control. Massive quantities of material, ie, ores, solvents, additives, and gangue, must be handled for separation procedures. Most mined ore undergoes size reduction, ie, grinding or crushing, and size separation and classification prior to minerals concentration.

Minerals separation or concentration methods may include ore sorting, gravity concentration, magnetic or electrostatic separations, flotation, or combinations of these methods, depending on the ore, the mineral, and economic considerations. These methods are described as are the various solid–liquid separation, ie, dewatering, procedures, which may include thickening, filtration, centrifugal dewatering, or thermal drying. The methods of choice for several minerals are given as examples.
Nitrogen Fixation
Authors: Newton William E.
Published: December 2005

Nitrogen fixation converts inert atmospheric molecular nitrogen gas into reduced forms whereby the nitrogen may be used by all life forms for protein and nucleic acid production. The biological process occurs only in microorganisms and is the principal contributor of fixed nitrogen to the biosphere. Fixed nitrogen is also derived from nonbiological processes, eg, fires, volcanoes, and lightning, and from commercial fertilizer production. The Haber‐Bosch ammonia process is highly energy efficient and is the most economical industrial process available. The most important source of biologically fixed nitrogen for agriculture is the symbiotic system that involves leguminous plants, which harbor rhizobia bacteria in nodules on their roots. Smaller contributions are made by other, less formal systems and by free‐living microbes. All of the biological systems use a similar metalloenzyme complex, called nitrogenase. Biological nitrogen fixation is discussed from a biochemical‐genetic viewpoint, as well as in terms of model chemistry and comparisons with the commercial process. Chemical approaches aimed at duplicating the biological process are also presented.
Polyamides, Aromatic
Authors: Gallini J.
Published: December 2005

This article describes the preparation and properties of aromatic polyamides and the fibers and films made from those polymers. A number of such polymers are identified, but the main focus is on the relatively few polymers that have achieved commercial status, namely, poly(
m
‐phenylene isophthalamide), poly(
p
‐phenylene terephthalamide), and copoly(
p
‐phenylene/3,4′‐diphenyl ether terephthalamide). The processes for manufacture of the corresponding monomers for these three polymers are described briefly. Both laboratory and commercial scale processes for the preparation of the polymers are presented and the processes for the commercial production of the fibers and films from these polymers are described. Properties of the polymers and the commercial fibers and films are tabulated. These products include Teijinconex®, Nomex®, Kevlar®, Twaron®, Technora®, Aramica®, and Mictron®. The principal end uses are described. Estimates of current sales volumes are cited, along with price ranges for the products. Health and safety concerns are identified.
Propylene
Authors: Calamur Narasimhan , Carrera Martin ,   Updated by Staff
Published: December 2005

Propylene is an important industrial chemical used as a feedstock in the production of polypropylene, acrylonitrile, propylene oxide, 2‐propanol, alkylated fuels, and other chemicals. It is obtained from steam cracking in pyrolysis furnaces in olefins plants and in refinery catalytic‐cracking reactors. Distillation in multitray columns yields purities in excess of 99.5 wt%. The physical and chemical properties of propylene are well characterized. Under ambient conditions, it is a colorless gas and has anesthetic properties at high concentrations. Propylene is usually transported in the liquid state at high pressures. Proper precautions must be taken when handling propylene.
Microwave‐Assisted Fast Cyclohexane Oxygenation Catalyzed by Iron‐Substituted Polyoxotungstates
Authors: Bonchio Marcella , Carraro Mauro , Scorrano Gianfranco , Kortz Ulrich
Published: December 2005

Under microwave irradiation, iron‐substituted polyoxotungstates (Fe‐POMs) catalyze cyclohexane oxygenation to A/K oil with 90–95% selectivity, unmatched turnover frequencies (40–400 h−1), and multi‐turnover regime (>1000 TON). Such a rapid reaction protocol allowed the screening of so‐called inorganic Fe‐synzymes with 1–4 nuclearity, including a family of Krebs‐type isostructural complexes. Product distribution, kinetic analysis, mechanistic probes and fitting calculations, are consistent with a radical chain oxidation propagated by Fe‐catalysed decomposition of organic peroxides which ultimately depends on the redox‐properties and structural arrangement of the iron moiety within the POM cage.
Improved Turnover Numbers in Palladium‐Catalyzed Bisdiene Cyclization‐Trapping using N‐Heterocyclic Carbene Ligands
Authors: Takacs James M. , Layek Suman , Palencia Hector , Andrews Ross N.
Published: December 2005

An optimized palladium‐N‐heterocyclic carbene catalyst system effects the palladium‐catalyzed bisdiene cyclization‐trapping with phenol at the 0.01% catalyst loading level with a TON of 7.6×103and TOF of 280 h−1, values much higher than typically found for this and related carbocyclizations. The reaction scales well and thetrans‐substituted six‐membered ring product is obtained in excellent yield on a 10‐mmole scale without further optimization of the catalyst system or reaction conditions.
Layered Double Hydroxide Supported Nanoplatinum and Nanopalladium Catalyzed Allylation of Aldehydes: A Mechanistic Study
Authors: Choudary B. M. , Roy Moumita , Roy Sarabindu , Lakshmi Kantam M. , Jyothi Karangula , Sreedhar Bojja
Published: December 2005

Layered double hydroxide (LDH)‐supported nanoplatinum(0) and nanopalladium(0) catalysts were prepared by a simple ion exchange technique and subsequent reduction with hydrazine hydrate and used for the allylation of aldehydes to give moderate to good yields of homoallylic alcohols. Detailed mechanistic studies of LDH‐Pd(0)‐catalyzed allylation using XPS and TGA‐MS reveal that a monoallyl‐palladium complex is the key intermediate for the catalytic cycle.
Pd‐Catalyzed ortho‐Selective Oxidative Coupling of Halogenated Acetanilides with Acrylates
Authors: Lee George T. , Jiang Xinglong , Prasad Kapa , Repič Oljan , Blacklock Thomas J.
Published: December 2005

Coupling of different halogenated acetanilides with acrylates using Pd‐catalyzed ortho‐selective CH bond activation is reported. The yields of coupled products are low to high depending on the substrate. In general, arenes with electron‐rich substituents like methoxy and methyl groups gave higher yields of the coupled products. The presence of the halogen substituent did not interfere with the activation process under these conditions
Taking “Nothing” into Consideration: Supported Metal Catalysts by SAXS
Authors: Pagliaro Mario
Published: December 2005

The analysis of the X‐ray diffraction patterns scattered at small‐angles (SAXS) by porous materials is a powerful analytical tool providing relevant structural information on supported metals used as heterogeneous catalysts. In particular, the technique offers valuable structural insights on the interphases which govern the chemical behaviour of these materials. Using a series of silica‐supported palladium catalysts we show how SAXS experiments address the crucial importance of porosity (or “nothing”) in affecting the structure of these catalysts.
Lithium Perchlorate‐Catalyzed Boc Protection of Amines and Amine Derivatives
Authors: Heydari Akbar , Hosseini Seyed Esmaeil
Published: December 2005

A new mild and chemoselective method for mono‐N‐protection of amines and amine derivatives as tert‐butoxycarbonyl derivatives is reported. The reaction proceeds with lithium perchlorate (20 mol %) and pyrocarbonates, and shows general applicability. The catalytic action of LiClO4 is specific for the activation of Boc2O, thus acid‐sensitive functionalities of the starting materials remain unchanged in the protection process. This procedure works well for sterically hindered primary amine as well as electron‐deficient primary arylamines, primary and secondary amino alcohols, α‐amino acid esters, hydroxylamines, hydrazines and sulfonamides.
Pronounced Catalytic Effect of Micellar Solution of Sodium Dodecyl Sulfate (SDS) for Regioselective Iodination of Aromatic Compounds with a Sodium Iodide/Cerium(IV) Trihydroxide Hydroperoxide System
Authors: Firouzabadi Habib , Iranpoor Nasser , Garzan Atefeh
Published: December 2005

Micellar solutions of sodium dodecyl sulfate (SDS) catalyze the regioselective iodination of a wide range of aromatic compounds with sodium iodide in the presence of the easily prepared, water‐resistant and recyclable cerium(IV) trihydroxide hydroperoxide, Ce(OH)3O2H, at room temperature. By this protocol, structurally diverse aromatic compounds including benzene and naphthalene were iodinated in good to excellent yields.
Transfer Hydrogenation of α‐Branched Ketimines: Enantioselective Synthesis of Cycloalkylamines via Dynamic Kinetic Resolution
Authors: Ros Abel , Magriz Antonio , Dietrich Hansjörg , Ford Mark , Fernández Rosario , Lassaletta José M.
Published: December 2005

The transfer hydrogenation of 2‐substituted bicyclic and monocyclic ketimines using HCO2H/ Et3N as the hydrogen source and TsDPEN‐based Ru(II) and Ir(III) catalysts proceeds with dynamic kinetic resolution to afford the corresponding cis‐cycloalkylamines with moderate to excellent levels of diastero‐ and enantioselectivity. A “one‐pot” procedure starting from ketones as starting materials with in situ formation of the reacting imines has also been developed.
Nutrition and health at contact in late prehistoric central Gulf Coast Florida
Authors: Hutchinson Dale L. , Norr Lynette
Published: December 2005

This paper presents an analysis of human remains from Tatham Mound, a dual‐component mortuary site from central Gulf Coast Florida. The human remains from Tatham are significant because they come from a limited time period during the initial contact with Europeans at AD 1525–1550. Dietary reconstruction demonstrates that at the time of European contact, maize was not a predominant dietary item. Low frequencies for several dental and skeletal pathological indicators are consistent with relatively good health as compared to other Southeastern late prehistoric and protohistoric populations. Despite the limited time period represented by the mound population, critical interactions occurred between Native Americans and Spaniards, as indicated by skeletal elements severed by metal weapons. The Tatham population is significant because it is one of the earliest studied populations contacted by Europeans in North America, and the only one with well‐documented sharp‐force trauma that represents intergroup hostility. Am J Phys Anthropol, 2006. © 2005 Wiley‐Liss, Inc.
On‐line photodecomposition for the determination of antimony species
Authors: Miravet R. , Bonilla E. , López‐Sánchez J. F. , Rubio R.
Published: December 2005

On‐line UV photooxidation by peroxodisulfate was coupled to ion chromatography hydride generation atomic fluorescence spectroscopy (IC‐UV‐HG‐AFS) for the speciation of inorganic antimony [Sb(III) and Sb(V)] and methylated species. Several parameters (UV lamp, irradiation time and peroxodisulfate concentration) that greatly influence the sensitivity of these three antimony species were investigated in depth. Under optimized conditions, photodecomposition resulted in an improvement in methylantimony species sensitivity. Dilution in di‐ammonium tartrate medium was necessary in order to ensure short‐term stability of Sb(III) at the µg l−1 concentration level. Furthermore, the efficiency of irradiation was strongly dependent on the chemical composition of the measured solution. Detection limits of 0.04 µg l−1 for Sb(V), 0.03 µg l−1 for Me3SbCl2 and 0.03 µg l−1 for Sb(III) as well as repeatability and reproducibility better than 4 and 8% RSD, respectively, were obtained. The proposed methodology was applied for antimony speciation in terrestrial plant sample extracts. Copyright © 2005 John Wiley & Sons, Ltd.
Spontaneous development of synovitis and cartilage degeneration in transgenic mice overexpressing cathepsin K
Authors: Morko Jukka , Kiviranta Riku , Joronen Kirsi , Säämänen Anna‐Marja , Vuorio Eero , Salminen‐Mankonen Heli
Published: December 2005

Objective

Several recent studies have demonstrated that cathepsin K, a proteolytic enzyme capable of degrading native fibrillar collagen, is overexpressed in osteoarthritic cartilage and inflamed synovial tissue. However, it is not known whether increased cathepsin K production is a primary or a secondary event in these diseases. The availability of transgenic UTU17 mice, which exhibit constitutive overexpression of the cathepsin K gene, prompted us to study possible arthritic changes in their knee joints.

Methods

Progression of synovitis and articular cartilage degeneration in the knee joints of UTU17 mice and their nontransgenic littermates was monitored by histologic analyses at 7 and 12 months of age. Distribution of cathepsin K in the knee joints was studied by immunohistochemistry.

Results

At the age of 7 months, UTU17 mice exhibited clear signs of synovitis, with strong immunostaining for cathepsin K in the synovial lining and the stroma, while control knee joints appeared normal. At 12 months, marked synovial thickening and fibrosis and severe degradation of cartilage and subchondral bone were observed in UTU17 mouse knee joints. In areas of cartilage degeneration, both chondrocytes and cells of hypertrophic synovia were positive for cathepsin K. At 12 months, synovia of control mice revealed only a few isolated cathepsin K–positive cells and mild changes in articular cartilage.

Conclusion

Our findings demonstrate that overexpression of the cathepsin K gene under its own promoter in transgenic mice makes them susceptible to progressive synovitis, which, upon aging, results in synovial hyperplasia and fibrosis and subsequent destruction of articular cartilage and bone.
Ridge directional singular points for fingerprint recognition and matching
Authors: Dagher Issam , Badawi Mustafa , Beyrouti Bassam
Published: December 2005

In this paper, a new approach to extract singular points in a fingerprint image is presented. It is usually difficult to locate the exact position of a core or a delta due to the noisy nature of fingerprint images. These points are the most widely used for fingerprint classification and matching. Image enhancement, thinning, cropping, and alignment are used for minutiae extraction. Based on the Poincaré curve obtained from the directional image, our algorithm extracts the singular points in a fingerprint with high accuracy. It examines ridge directions when singular points are missing. The algorithm has been tested for classification performance on the NIST‐4 fingerprint database and found to give better results than the neural networks algorithm. Copyright © 2005 John Wiley & Sons, Ltd.
Lateral root bridging as a strategy to enhance L‐DOPA production in Stizolobium hassjoo hairy root cultures by using a mesh hindrance mist trickling bioreactor
Authors: Sung Lin‐Shiang , Huang Shih‐Yow
Published: December 2005

Stizolobium hassjoo hairy roots exhibited a lateral root bridging behavior, enabling not only root dry weight but enhancement of intracellular L‐DOPA content. When a single root tip was exerted a proper hindrance, the primary root growth was inhibited while lateral roots were profusely induced. The hindrance‐induced lateral roots from individual primary root could bridge together under appropriate inoculation densities, leading to high density hairy root cultures producing secondary metabolites. In the present paper, a novel bioreactor was proposed based on a strategy of lateral root bridging by utilizing mesh as a hindrance, called “mesh hindrance mist trickling bioreactor (MHMTB)”. Significant improvements of dry weight and L‐DOPA production by using MHMTB were 1.8 and 2.2‐folds, respectively, higher than those in the control run without the mesh hindrance within the root bed. © 2005 Wiley Periodicals, Inc.
Selection of patients with hepatocellular carcinoma for liver transplantation
Authors: Sutcliffe R , Maguire D , Portmann B , Rela M , Heaton N
Published: December 2005

Background

Orthotopic liver transplantation (OLT) plays a pivotal role in the management of selected patients with initial hepatocellular carcinoma (HCC). After disappointing early results and a shortage of cadaveric grafts, patients are currently selected for OLT on the basis of tumour size and number. Limitations of these criteria and the advent of living donation have prompted their re-evaluation. The principal aims of this review were to define the limitations of current transplant criteria for HCC, and to identify potential areas for improvement.

Methods

A Medline search using the terms ‘liver transplantation’ and ‘hepatocellular carcinoma’ was conducted. Additional references were sourced from key articles.

Results and conclusion

In patients with HCC, biological properties of the tumour are more accurate than radiological criteria in determining outcome after transplantation. Despite the risks of tumour biopsy, which may have been previously overstated, histological evaluation before transplantation may have a role and warrants further study. By expanding the donor pool and eliminating waiting times, live donor liver transplantation is a valuable resource that has yet to fulfil its potential because of unresolved ethical issues concerning the safety of the donor. The availability of long-term outcome data may help to clarify this in the near future.
Prehospital ultrasound imaging improves management of abdominal trauma
Authors: Walcher F , Weinlich M , Conrad G , Schweigkofler U , Breitkreutz R , Kirschning T , Marzi I
Published: December 2005

Background

Blunt abdominal trauma with intra-abdominal bleeding is often underdiagnosed or even overlooked at trauma scenes. The purpose of this prospective, multicentre study was to compare the accuracy of physical examination and prehospital focused abdominal sonography for trauma (PFAST) to detect abdominal bleeding.

Methods

Six rescue centres took part in the study from December 2002 to December 2003, including 230 patients with suspected abdominal injury. The accuracy of physical examination at the scene and PFAST were compared. Later examinations in the emergency department (ultrasonography and/or computed tomography) were used as the reference standard.

Results

The complete protocol and follow-up was obtained in 202 patients. The sensitivity, specificity and accuracy of PFAST were 93 per cent, 99 per cent and 99 per cent, respectively, compared with 93 per cent, 52 per cent and 57 per cent for physical examination at the scene. Scanning with PFAST occurred a mean(s.d.) 35(13) min earlier than ultrasound in the emergency department. Abdominal bleeding was detected in 14 per cent of patients. Using PFAST led to a change in either prehospital therapy or management in 30 per cent of patients, and a change to admitting hospital in 22 per cent.

Conclusion

In this study, PFAST was a useful and reliable diagnostic tool when used as part of surgical triage at the trauma scene.
The Solution Structure of the AppA BLUF Domain: Insight into the Mechanism of Light‐Induced Signaling
Authors: Grinstead Jeffrey S. , Hsu Shang‐Te D. , Laan Wouter , Bonvin Alexandre M. J. J. , Hellingwerf Klaas J. , Boelens Rolf , Kaptein Robert
Published: December 2005

The transcriptional antirepressor AppA from the photosynthetic bacterium Rhodobacter sphaeroides senses both the light climate and the intracellular redox state. Under aerobic conditions in the dark, AppA binds to and thereby blocks the function of PpsR, a transcriptional repressor. Absorption of a blue photon dissociates AppA from PpsR and allows the latter to repress photosynthesis gene expression. The N terminus of AppA contains sequence homology to flavin‐containing photoreceptors that belong to the BLUF family. Structural and chemical aspects of signal transduction mediated by AppA are still largely unknown. Here we present NMR studies of the N‐terminal flavin‐binding BLUF domain of AppA. Its solution structure adopts an α/β‐sandwich fold with a βαββαββ topology, which represents a new flavin‐binding fold. Considerable disorder is observed for residues near the chromophore due to conformational exchange. This disorder is observed both in the dark and in the light‐induced signaling state of AppA. Furthermore, we detect light‐induced structural changes in a patch of surface residues that provide a structural link between light absorption and signal‐transduction events.
Enhanced Photocatalytic Activity of Zeolite‐Encapsulated TiO2 Clusters by Complexation with Organic Additives and N‐Doping
Authors: Alvaro Mercedes , Carbonell Esther , Fornés Vicente , García Hermenegildo
Published: December 2005

In the literature it was found that titanium oxide clusters of a few metal atoms encapsulated inside the micropores of zeolite Y exhibit large blue shifts in the TiO ligand‐to‐metal charge‐transfer band as compared to non‐encapsulated bulk titanium dioxide particles. This blue shift of the TiO absorption band is believed to have a negative effect on the photocatalytic activity of zeolite‐encapsulated TiO2. We report here on circumventing this problem and increasing visible‐light absorption by means of a red shift of the absorption band caused by addition of some organic molecular modifiers containing acidic OH groups that can strongly bind with titanol groups TiOH. In the studied series of zeolite‐encapsulated TiO2 samples, the red shift of the optical spectrum follows the order: catechol>4‐aminobenzoic acid>benzoic acid. Also N‐doping of zeolite‐encapsulated TiO2 clusters by thermal treatment with urea leads to a red shift of the TiO2 absorption band that depends on the annealing and hydration conditions. By comparison to the degradation of phenol in aqueous solution, we have demonstrated that these changes in the absorption spectrum on addition of the organic modifier are also reflected in the photocatalytic activity of the samples; a greater increase in photocatalytic activity (about 30 %) was observed for the additive catechol.