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PubMed2004

Extended metal atom chains (EMACs) of five chromium or cobalt atoms: symmetrical or unsymmetrical?

Structural studies of pentachromium and pentacobalt extended metal atom chain (EMAC) systems are presented in which the metal chains are helically wrapped by either the pentadentate dianion tripyridyldiamide (tpda) or its diethyl-substituted analogue bis(4-ethyl-2-pyridylamido)pyridine (etpda). The compound Cr(5)(tpda)(4)(NCS)(2), has alternating long and short Cr-Cr distances, contrary to recent reports that describe it as symmetrical with essentially equally spaced chromium atoms. The linear Cr(5)(10+) chain is composed of two Cr(2)(4+) quadruply bonded units and an isolated high spin Cr(II) unit. The new compounds Cr(5)(etpda)(4)Cl(2), [Cr(5)(etpda)(4)FCl]PF(6), and Co(5)(etpda)(4)(NCS)(2)() employ the etpda ligand as "insulation" around a central pentametal-atom "wire." Compound, like all other oxidized pentachromium compounds, has very disparate alternating short-long-short-long Cr-Cr distances, 2.032(3) A, 2.560(6) A, 1.873(5) A, and 2.509(4) A. Compound shows a nearly uniform spacing of the Co atoms, although the outer Co-Co distances (2.279[4] A) are slightly longer than the inner ones (2.239[4] A).

Journal Article↗
PubMed2000

Mass spectrometric study of tricarbonyl (eta(6)-phenyl methanols) of chromium(0).

A mass spectrometric study of several tricarbonyl (eta(6)-phenyl methanols) of chromium(0) was performed. Electron ionization (EI), chemical ionization (CI) and fast atom bombardment (FAB) mass spectra were acquired for each molecule, and compared in order to establish a general fragmentation pattern. The suggested pathways were investigated and confirmed by means of constant b/e linked scans and high resolution data. In addition a Hammett-McLafferty correlation for some peaks derived from the molecular ions was accomplished.

Chromium↗
PubMed1995

Determination of heavy metals distribution in the anoxic sediment slurries by chemical sequential fractionation.

An analytical procedure involving chemical sequential fractionation was used for quantification of partitioning of some metals (Cu, Cr, and Cd) in anoxic sediment slurries (10 or 20% w/v) into six fractions. These fractions include exchangeable, bound to carbonate, easily reducible, moderately reducible, bound to organic, and residue fractions. Low amounts of Cu (10-11%) and moderate amounts of Cr (38%) and Cd (38-39%) were retained as the easily reducible and moderately reducible fractions which represented the mobile forms of metals in the sediments. The amendment of different amounts (20 or 100 mg/liter) of metals into the anoxic sediment slurries (10% w/v) resulted in a different percentage distribution of metals into six fractions. The amount of Cd in the carbonate fraction increased significantly after Cd amendment. The percentage of Cu or Cr in the easily reducible and moderately reducible fractions increased, while those in the residual fraction decreased as the amount of Cu or Cr amended into the sediment slurries increased.

Cadmium↗
PubMed1976

Nuclear stains with soluble metachrome metal mordant dye lakes. The effect of chemical endgroup blocking reactions and the artificial introduction of acid groups into tissues.

Following our study on the effect of deoxyribonucleic acid (DNA) extraction on nuclear staining with soluble metal mordant dye lakes covering 29 dye lakes we chose a series of lakes representing the three groups: (1) readily prevented by DNA removal, (2) weakened by DNA extraction but not prevented, (3) unaffected by DNA removal, for application of other endgroup blockade reactions. The lakes selected were alum and iron hematoxylins, iron alum and ferrous sulfate galleins, Fe2+ gallo blue E, iron alum celestin blue B, iron alum fluorone black and the phenocyanin TC-FeSO4 sequence. Azure A with and without an eosin B neutral stain, was used as a simple cationic (and anionic) dye control. Methylation was less effective than with simple cationic dyes, but did weaken celestin blue, gallo blue E and phenocyanin Fe2+ nuclear stains. These dyes also demonstrate other acid groups: acid mucins, cartilage matrix, mast cells, central nervous corpora amylacea and artificially introduced carboxyl, sulfuric and sulfonic acid groups. Alum hematoxylin stained cartilage weakly and demonstrated sulfation and sulfonation sites. The iron galleins, iron fluorone black and acid iron hematoxylin do not. A pH 4 iron alum hematoxylin gave no staining of these sites; an alum hematoxylin acidified with 1% 12 N HCl gave weaker results. Deamination prevented eosin and orange G counterstains but did not impair nuclear stains with any of the mordant dye lakes. The simple acetylations likewise did not alter mordant dye nuclear staining, the Skraup reagent gave its usual sulfation effect on other tissue elements, but did not alter nuclear stains by mordant dyes. The mordant dyes do not bind to periodic acid engendered aldehyde sites and p-toluidine/acetic acid and borohydride aldehyde blockades did not alter mordant dye lake nuclear staining. Nitration by tetranitromethane, which blocks azo coupling of tyrosine residues, did not alter nuclear staining by the mordant dye lakes. Benzil at pH 13, which prevents the beta-naphthoquinone-4-Na sulfonate (NQS) arginine reaction and the Fullmer reaction of basic nucleoprotein, did not affect iron gallein, iron or alum hematoxylin stains of nuclei or lingual keratohyalin.

Aldehydes↗
PubMed1991

Effects of iron(III) analogs on growth and pseudobactin synthesis in a chromiumtolerant Pseudomonas isolate.

The growth and siderophore production of a fluorescent Pseudomonas species isolated from soil contaminated with chromium was found to be influenced by the presence of trivalent cations. Overproduction of pseudobactin occurred when the isolate was grown in media containing 1 mM Cr(III) under iron-limited conditions but not when Fe(III) was added at 10 microM. Pseudobactin synthesis was derepressed in iron-limited cultures containing 1 mM Sc(III) or Y(III), examples of group III-B elements. We found that Al(III), Ga(III) or In(III), representative metals from group III-A, repressed synthesis of pseudobactin under iron-deficient conditions. Analogs of Fe(III) were found to inhibit growth of the Pseudomonas isolate in iron-limited media and the trivalent metals listed in order of decreasing toxicity were as follows: Ga greater than In greater than Sc greater than Cr greater than Y greater than Al. The inhibition of growth by 1 mM In(III), Sc(III) and Ga(III) was greater during iron-limited growth than in media containing 10 microM Fe(III). These data show that, although the metal analogs of Fe(III) have similar chemical and physical characteristics, the physiological response of the fluorescent pseudomonad when grown in the presence of these metals varied markedly.

Chromium↗
PubMed1985

Alterations of alveolar macrophage function and level of bronchopulmonary protease inhibitors in O,O,S-trimethyl phosphorothioate-induced lung injury.

O,O,S-Trimethyl phosphorothioate (OOS-TMP), an impurity present in widely used organophosphorus insecticides, has been shown to induce pneumotoxicity after oral administration. To date very little is known about the pathogenesis of the injury. Protease-anti-protease imbalance has been proposed as a mechanism of various lung injuries; thus, the effect of OOS-TMP on alpha 1-protease inhibitor capacity, pulmonary alveolar macrophage (PAM) esterases, cytotoxic activity and on specific esterase inhibitors in the bronchopulmonary lavage fluid and serum were measured. OOS-TMP (20 mg/kg) administered orally to rats produced a 27% increase in PAM esterase activity 6 h after treatment. The activity then declined to 63% of control value on day 3 and had not recovered to any significant extent on day 7. The cytotoxic activity of PAM was significantly increased at 6 h and 24 h following treatment. Chymotrypsin inhibitory capacity (CIC) of the lavage fluid was decreased by 45% at 6 h but recovered rapidly and reached control levels by 24 h. Trypsin inhibitory capacity (TIC) of serum was affected to a lesser extent such that no change was detected after 6, 12 or 24 h. These data, early elevation of PAM esterase levels with a concomitant increase in cytotoxic activity and decreased TIC and CIC in bronchopulmonary lavage fluid, support the view that pathogenesis of OOS-TMP produced lung injury could be due to increased protease levels.

Administration, Oral↗
PubMed2004

A Schiff base complex of chromium(III): an efficient inhibitor for the pathogenic and invasive potential of Shigella dysenteriae.

A Schiff base complex of chromium(III), transdiaqua[N,N'ethylenebis (salicylideneimine)chromium(III)]perchlorate, [Cr(salen)(OH(2))(2)](+), was found to have an inhibitory effect on the growth of Shigella dysenteriae. The chromium(III) complex was found to cure (remove) the invasive plasmid and thereby render the microbe more sensitive to the tested antibiotics. The loss in the catalytic activity of the isolated endo-alpha-N-acetyl galactosaminidase on mucin as a substrate was also observed in the presence of [Cr(salen)(OH(2))(2)](+). This suggests that [Cr(salen)(OH(2))(2)](+) is toxic to the microbe and could make the microbe non-pathogenic and non-invasive, thus establishing its role in microbiological applications to reduce the toxic potentials of a microbe.

Animals↗
PubMed2005

Sorptive removal of trivalent and hexavalent chromium from binary aqueous solutions by composite alginate-goethite beads.

In this study, the removal of hexavalent and trivalent chromium ions from binary aqueous solutions by composite alginate-goethite beads was investigated in a batch mode. Equilibrium sorption experiments were carried out at different temperatures and pH values. The data were correlated with Langmuir and Freundlich equations. The thermodynamic parameters calculated were: change in free energy, in enthalpy, in entropy and the heat of adsorption. The influence of mixing rate, sorbent concentration and sorbent particle size was studied at kinetic runs. The effective diffusion coefficients were evaluated by employing the homogeneous diffusion model and the shrinking core model for hexavalent and trivalent chromium, respectively. Desorption experiments were conducted by employing various eluants showed that the loaded material could be regenerated satisfactorily.

Absorption↗
PubMed1999

Determination of total chromium in phosphate rocks by ion chromatography.

Chromium(VI) is one of seven elements which is classified in the fertilizer industry as being harmful to plants and biological systems. Phosphate rocks represent the raw material for complex fertilizer production in the world. This paper investigates for the first time the determination of total chromium in phosphate rocks by ion chromatography. The developed analytical method involves the digestion of phosphate rocks with nitric acid followed by sample treatment of the resulting solution. The digestion solution obtained was treated with an oxidising agent (potassium peroxosulphate) to convert all chromium to the hexavalent state. The analytical method developed utilizes anion-exchange ion chromatography to achieve the separation and spectrophotometric post-column reaction for detection with diphenylcarbazide. The relative standard of deviation from analytical data comparison of six different phosphate rocks with atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry techniques, and cross-analysis data against an internationally certified phosphate rock standard were between 0.58 and 1.45%. Calibration curve between 0.2 and 0.9 microgram/ml was excellent, and the method has a detection limit for Cr(VI) of 0.05 ng. The developed method offers a fast, a reliable and an alternative procedure for the determination of total chromium in phosphate rock deposits by ion chromatography.

Chromatography, Ion Exchange↗
PubMed2000

Element selective detection for supercritical-fluid chromatography.

This manuscript describes the use of Supercritical-Fluid Chromatography (SFC) with plasma spectrometric detection for the analysis of organometallics. An introduction on the principles and characteristics of Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is included, along with a discussion about requirements for coupling SFC to plasma detection and the different approaches for interfacing SFC to ICP. The last part of this review paper provides a comprehensive description of SFC-ICP applications for the analysis of organometallics containing iron, silicon, tin, chromium, arsenic, lead, mercury and antimony.

Antimony↗
PubMed2003

Monocrystalline diamond paste-based electrodes and their applications for the determination of Fe(II) in vitamins.

A new class of electrochemical sensors, namely, electrodes based on diamond paste, was designed using monocrystalline diamond (natural diamond 1 microm and synthetic diamond, 50 microm (synthetic-1) and 1 microm (synthetic-2)) powder and paraffin oil. The characterization of the electrodes was performed using cyclic voltammetry and differential pulse voltammetry. Fe(II) was determined by differential pulse voltammetry (DPV) at 75 mV (vs Ag/AgCl) using all diamond paste-based electrodes. The linear concentration range was between 10(-8) and 10(-4) mol/L for both the natural diamond and synthetic-2 with detection limits of 10(-10) and 10(-9) mol/L, respectively, whereas the linear concentration range for synthetic-1 was between 10(-7) and 10(-3) mol/L with a detection limit of 10(-8) mol/L Fe(II) was determined successfully from four types of pharmaceutical products. The recovery values of Fe(II) in the pharmaceutical products were higher than 98.00% with relative standard deviation values < 5%.

Carbon↗
PubMed1996

Electrocatalytic reduction of nitric oxide at electrodes modified with electropolymerized films of [Cr(v-tpy)2]3+ and their application to cellular NO determinations.

Nitric oxide can be electrocatalytically reduced at electrodes modified with electropolymerized films of [Cr(v-tpy)2]3+. Upon further modification with a thin film of Nafion (to prevent interferences from anions, especially nitrite), these electrodes can be employed as NO sensors in solution with submicromolar detection limits and fast response. We have carried out preliminary studies of cellular NO release from Rhodobacter sphaeroides bacterial cells with excellent results.

Catalysis↗
PubMed2002

Asymmetric catalysis of hetero-ene reactions with tridentate Schiff base chromium(III) complexes.

Tridentate Schiff base chromium(III) complex 1 catalyzes the asymmetric hetero-ene reaction between aryl aldehydes and either 2-methoxypropene or 2-trimethylsilyloxypropene to provide a series of beta-hydroxyenol ether products in high yields and enantioselectivities. X-ray crystallographic analysis of a closely related chromium complex reveals a bridged, dimeric structure bearing aquo-bound six-coordinate Cr(III) centers. A mechanism is proposed wherein water dissociation is effected by means of a chemical desiccant (BaO or silyl enol ether), thereby revealing the site for aldehyde complexation.

Benzaldehydes↗
PubMed2002

Chemospecific chromium[VI] catalyzed oxidation of C-H bonds at -40 degrees C1.

H5IO6 in the presence of catalytic chromoyl diacetate is a powerful method for oxidation of C-H bonds. Tertiary and oxygen activated C-H bonds are oxidized to tertiary alcohols or ketones at temperatures as low as -40 degrees C. The putative reagent is neutral dioxoperoxy chromium[VI] which undergoes C-H oxidation with retention of stereochemistry. This reagent appears to be the first reagent capable of oxidation of a C-H bond in the presence of an olefin without concomitant epoxidation.

Catalysis↗
PubMed2005

Luminescent silole nanoparticles as chemoselective sensors for Cr(VI).

Colloidal suspensions of 3-aminopropylmethyl(tetraphenyl)silole nanoparticles can be used as selective chemosensors for carcinogenic chromium(VI) analyte. Methylhydrosilole is functionalized by hydrosilation of allylamine, and the colloid is prepared by the rapid addition of water to a THF solution of the silole. The method of detection is through electron-transfer quenching of the fluorescence of the silole colloid (lambda(em) = 485 nm at 360 nm excitation) by the analytes, with hundred parts per billion detection limits. Stern-Volmer plots are linear up to 10 ppm in the case of chromium, but exhibit saturation behavior near 5-10 ppm for arsenic. Dynamic light scattering experiments and AFM measurements show the particle sizes to be around 100 nm in diameter and dependent on solvent composition, with a particle size dispersity of +/-25%. The fluorescence lifetimes of the silole in solution and colloid are approximately 31 ps and approximately 4.3 ns, respectively, while the silole has a lifetime of 6 ns in the bulk solid. A minimum volume fraction of 80% water is necessary to precipitate the colloid from THF, and the luminescence continues to rise with higher water fractions. Colloids in a pH 7 phosphate-buffered suspension show both higher sensitivity and greater selectivity (100-fold) for CrO4(2-) detection than for other oxoanion interferents, NO3-, NO2-, SO4(2-), and ClO4-.

Chromium↗
PubMed2006

Unprecedented reactivity pattern of chromium fischer carbene complexes. Direct application to one-pot synthesis of 4-aryl-3,4-dihydrocoumarins on a multigram scale.

[reaction: see text] Reaction of alkenyl carbene chromium(0) complexes and ketene acetals triggers the formation of 4-aryl-3,4-dihydrocoumarins. The reaction can be carried out as a simple one-pot protocol in air atmosphere. The huge interest of dihydrocoumarins has prompted us to optimize a multigram-scale process.

Chromium↗
PubMed1999

A novel chromium(0)-promoted four-component cycloaddition reaction.

[formula: see text] Reaction of (eta 6-thiepin-1,1-dioxide)tricarbonylchromium(0) with excess terminal alkynes under photoactivation conditions affords novel pentacyclic adducts formally derived from a sequential [6 pi + 2 pi]/[6 pi + 2 pi]/[2 sigma + 2 pi] cycloaddition process.

Alkynes↗