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Molar Equivalent (molar + equivalent)

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Chemistry88%

Selected Abstracts

Structural and functional responses of river biofilm communities to the nonsteroidal anti-inflammatory diclofenac

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2007
John R. Lawrence
Abstract Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID) that has been detected widely in surface waters in North America and Europe. The impact of diclofenac on river biofilm communities was investigated at exposures of 10 and 100 ,g L,1 of diclofenac or its molar equivalent in carbon and nutrients. Experiments were carried out with river water during spring and summer using rotating annular reactors as model systems. Diclofenac or nutrients at 10 ,g L,1 were observed to have no significant effect on algal, bacterial, and cyanobacterial biomass in spring, whereas in the summer the nutrient equivalent reduced algal biomass and diclofenac reduced cyanobacterial biomass relative to control biofilms (p < 0.05). In contrast, at 100 ,g L,1 diclofenac or nutrients, the result was increased cyanobacterial and bacterial biomass, respectively, relative to control biofilms in spring. In summer, 100 ,g L,1 diclofenac significantly increased bacterial biomass and the nutrient treatment had no significant effect (p < 0.05); both treatments resulted in increased biofilm thickness. The glycoconjugate composition of the exopolysaccharide matrix was influenced differentially by the treatments in both seasons. Biolog assessments of carbon use indicated that 100 ,g L,1 diclofenac or nutrients resulted in significant depressions in the use of carbon sources in summer and significant increases in spring. Impacts on protozoan and micrometazoan populations also were assessed. Denaturing gradient gel electrophoresis analyses of community DNA and fluorescent in situ hybridization studies indicated that diclofenac had significant effects on the nature of the bacterial community in comparison with control and nutrient-treated river biofilm communities. [source]

The copper(II) complexes di-,-bromo-bis{[2,6-bis­(pyrazol-1-yl)­pyridine]­per­chlorato­copper(II)} and [2,6-bis(pyra­zol-1-yl)­pyridine]­di­bromo­copper(II)

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2004
Surajit Chakrabarty
The two title compounds, di-,-bromo-bis{[2,6-bis­(pyrazol-1-yl-,N2)­pyridine-,N](perchlorato-,O)copper(II)}, [Cu2Br2(ClO4)2(C11H9N5)2], (I), and [2,6-bis­(pyrazol-1-yl)­pyridine]­dibromo­copper(II), [CuBr2(C11H9N5)], (II), were synthesized by only slight modifications of the same reaction; compound (II) was formed by adding one molar equivalent of pyrazole (C3N2H4) to the reaction mixture of (I). Compound (I) is a bromo-bridged dinuclear copper(II) compound stabilized by weak interactions with the perchlorate anions (ClO4,), while (II) is a related mononuclear species, which has a distorted square-pyramidal geometry. [source]

Hydrolysis of C,N -chelated diorganotin(IV) chlorides and catalysis of transesterification reactions

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2009
ka Pad, lková
Abstract Diorganotin(IV) dichlorides of formula LCNRSnCl2 (where R is nBu or Ph) containing one LCN chelating ligand were hydrolyzed with aqueous sodium hydroxide in benzene. The composition of the products is strongly dependent on the amount of hydroxide. The partially hydrolyzed compounds of composition (LCNRSnCl)2(µ-O) were isolated as crystalline products. A hydrolysis where more than one molar equivalent of NaOH is employed gave only a mixture of unidentifiable products. The structure of (LCNPhSnCl)2(µ-O) was determined by X-ray diffraction techniques in the solid state. In solution there was a mixture of diastereoisomers found, where the tin atoms serve as a stereogenic centers. The catalytic activity of starting dichlorides as well as (LCNPhSnCl)2(µ-O) in various transesterification processes was investigated. The activity is very low in the case of starting dichlorides. When two molar equivalents of NaH are added or (LCNPhSnCl)2(µ-O) is employed in the catalytic experiments, the activity is comparable to the literature data. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Living Radical Polymerization of Acrylates Mediated by 1,3-Bis(2-pyridylimino)isoindolatocobalt(II) Complexes: Monitoring the Chain Growth at the Metal

CHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2008
Björn
Abstract A new type of mediator for cobalt(II)-mediated radical polymerization is reported which is based on 1,3-bis(2-pyridylimino)isoindolate (bpi) as ancillary ligand. The modular synthesis of the bis(pyridylimino)isoindoles (bpiH) employed in this work is based on the condensation of 2-aminopyridines with phthalodinitriles. Reaction of the bpiH protio-ligands with a twofold excess of cobalt(II) acetate or cobalt(II) acetylacetonate in methanol gave [Co(bpi)(OAc)], which crystallize as coordination polymers, and a series of [Co(acac)(bpi)(MeOH)], which are mononuclear octahedral complexes. Upon heating the [Co(acac)(bpi)(MeOH)] compounds to 100,°C under high vacuum, the coordinated methanol was removed to give the five-coordinate complexes [Co(acac)(bpi)]. The polymerization of methyl acrylate at 60,°C was investigated by using one molar equivalent of the relatively short-lived radical source 2,2,-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70) as initiator (monomer/catalyst/V-70: 600:1:1). The low solubility of the acetato complexes inhibits their significant activity as mediators in this reaction, whereas the acetylacetonate complexes control the radical polymerization of methyl acrylate more effectively. The radical polymerizations of the hexacoordinate complexes did not show a linear increase in number-average molecular weight (Mn) with conversion; however, the polydispersities were relatively low (PDI=1.12,1.40). By using the pentacoordinate complexes [Co(acac)(bpi)] as mediators, a linear increase in Mn values with conversion, which were very close to the theoretical values for living systems, and very low polydispersities (PDI<1.13) were obtained. This was also achieved in the block copolymerization of methyl acrylate and n -butyl acrylate. The intermediates with the growing acrylate polymer radical (.PA) were identified by liquid injection field desorption/ionization mass spectrometry as following the general formula [Co(acac)(4-methoxy-bpi)-(MA)n -R] (MA: methyl acrylate; R: C(CH3)(CH2C(CH3)2OCH3)CN), a notion also confirmed by NMR end-group analysis. [source]

Bonding and Bending in Zirconium(IV) and Hafnium(IV) Hydrazides

CHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2008
Heike Herrmann Dr.
Abstract Reaction of the dichloro complexes [M(N2TBSNpy)Cl2] (M=Zr: 1, Hf: 2; TBS: tBuMe2Si; py: pyridine) with one molar equivalent of LiNHNPh2 gave mixtures of the two diastereomeric chlorohydrazido(1,) complexes [M(N2TBSNpy)(NHNPh2)Cl] (M=Zr: 3,a,b, Hf: 4,a,b) in which the diphenylhydrazido(1,) ligand adopts a bent ,1 coordination. This mixture of isomers could be cleanly converted into the deep green diphenylhydrazido(2,) complexes [Zr(N2TBSNpy)(NNPh2)(py)] (5) and [Hf(N2TBSNpy)(NNPh2)(py)] (6), respectively, by dehydrohalogenation with lithium hexamethyldisilazide (LiHMDS) in the presence of one molar equivalent of pyridine. Both complexes contain a linearly coordinated hydrazinediide for which a DFT-based frontier orbital analysis established bonding through one , and two , orbitals. A high polarity of the MN bond was found, in accordance with the description of hydrazinediide(2,) acting as a six-electron donor ligand. The pyridine ligand in [M(N2TBSNpy)(NNPh2)(py)] (M=Zr: 5, Hf: 6) is substitutionally labile as established by line-shape analysis of the dynamic spectra (,G,=19,kcal,mol,1). A change in denticity of the hydrazido unit from ,1 to ,2 was studied by DFT methods. Both forms are calculated to be very close in energy and are only separated by shallow activation barriers, which supports the notion of a rapid ,1 to ,2 interconversion. This process is believed to happen early on in the NN scission in the presence of coupling reagents. Frontier orbital and natural population analyses suggest that a primarily charge-controlled nucleophilic attack at N, is unlikely whereas interaction with an electrophile could play an important role. This hypothesis was tested by the reaction of 5 and 6 with one molar equivalent of B(C6F5)3 to give [Zr(N2TBSNpy)(NNPh2){B(C6F5)3}] (7) and [Hf(N2TBSNpy)(NNPh2){B(C6F5)3}] (8). In these products, B(C6F5)3 becomes attached to the N, atom of the side-on bound hydrazinediide and there is an additional interaction of an ortho -F atom of a C6F5 ring with the metal centre. [source]

Substitution-reduction: an alternative process for the [18F]N -(2-fluoroethylation) of anilines

JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 4 2004
Emmanuelle Briard
Abstract Substitution of a halo atom (chloro or bromo) in easily prepared N -haloacetyl-anilines with no-carrier added (NCA) cyclotron-produced [18F]fluoride ion (18F, t1/2= 109.8 min; ,+=96.9%), followed by reduction with borane,tetrahydrofuran (BH3,THF), provides an alternative route to NCA [18F]N -(2-fluoroethyl)-anilines. This two-step and one-pot process is rapid (,50 min) and moderately high yielding (,40% decay-corrected radiochemical yield (RCY) overall). In the nucleophilic substitution reaction, 18-crown-6 is preferred to Kryptofix® 222 as complexing agent for the solubilization of the counter-ion (K+), derived from an added metal salt, in acetonitrile. Weakly basic potassium bicarbonate is preferred as the added metal salt. Inclusion of a small amount of water, equating to 4,5 molar equivalents relative to 18-crown-6, base or precursor (held in equimolar ratio), is beneficial in preventing the adsorption of radioactivity onto the wall of the glass reaction vessel and for achieving high RCY in the nucleophilic substitution reaction. BH3,THF is effective for the rapid reduction of the generated [18F]N -fluoroacetyl-aniline to the [18F]N -(2-fluoroethyl)-aniline. Copyright © 2004 John Wiley & Sons, Ltd. [source]

A novel trinuclear zinc(II) cluster with a tetrahedral ZnO4 core

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2009
Orde Q. Munro
The reaction of 0.67 molar equivalents of the O,N,O,-tridentate zwitterionic Schiff base (2Z,4E)-4-[(2-hydroxyphenyl)iminio]pent-2-en-2-olate (H2L) with one equivalent of zinc(II) acetate in methanol affords a novel trinuclear ZnII cluster, di-,-acetato-1:2,2O:O,;2:3,2O:O,-dimethanol-1,O,3,O -bis{,-2-[(2E,3Z)-4-oxidopent-3-en-2-ylideneamino]phenolato}-1:2,4O2,N,O4:O4;2:3,4O4:O2,N,O4 -trizinc(II), [Zn3(C11H11NO2)2(C2H3O2)2(CH4O)2], (I), in which two bridging acetate ligands link the terminal square-based pyramidal ZnII ions to the approximately tetrahedral ZnII ion at the core of the cluster. The ZnO4 coordination group of the central ZnII ion is established by two bridging phenolate and two bridging acetate O atoms. The remaining four coordination sites of each terminal ZnII ion are occupied by methanol and deprotonated H2L. Furthermore, the Zn-bound methanol hydroxyl groups are involved in complementary hydrogen bonding with the Zn-bound enolate O atom of a neighbouring molecule, about an inversion centre in each case. The structure of (I) is therefore best described as an extended one-dimensional hydrogen-bonded chain of trinuclear ZnII clusters. [source]

Hydrolysis of C,N -chelated diorganotin(IV) chlorides and catalysis of transesterification reactions

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2009
ka Pad, lková
Abstract Diorganotin(IV) dichlorides of formula LCNRSnCl2 (where R is nBu or Ph) containing one LCN chelating ligand were hydrolyzed with aqueous sodium hydroxide in benzene. The composition of the products is strongly dependent on the amount of hydroxide. The partially hydrolyzed compounds of composition (LCNRSnCl)2(µ-O) were isolated as crystalline products. A hydrolysis where more than one molar equivalent of NaOH is employed gave only a mixture of unidentifiable products. The structure of (LCNPhSnCl)2(µ-O) was determined by X-ray diffraction techniques in the solid state. In solution there was a mixture of diastereoisomers found, where the tin atoms serve as a stereogenic centers. The catalytic activity of starting dichlorides as well as (LCNPhSnCl)2(µ-O) in various transesterification processes was investigated. The activity is very low in the case of starting dichlorides. When two molar equivalents of NaH are added or (LCNPhSnCl)2(µ-O) is employed in the catalytic experiments, the activity is comparable to the literature data. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Novel Hypervalent Complexes of Main-Group Metals by Intramolecular Ligand,Metal Electron Transfer*

CHEMISTRY - A EUROPEAN JOURNAL, Issue 23 2004
Matthias Driess Prof. Dr.
Abstract New fascinating electronic features of the simple diketoamine chelate ligand HN[CH2C(tBu)O]2 (1) are described. Unexpectedly, the corresponding trianionic amido-dienolate form of 1 is capable of reducing main-group metal atoms M after initial coordination and intramolecular L,M two-electron transfer and of stabilizing main-group elements in unusual low oxidation states. This is impressively shown by the synthesis and structural characterization of the novel Ge and Sn complexes 4,6 by redox reactions of lithiated 1 with the corresponding metal halides GeCl4 and MCl2 (M=Ge, Sn). Surprisingly, conversion of tris-lithiated 1 with GeCl4 readily consumes two molar equivalents of GeCl4 and results in the formation of the neutral GeCl3 complex 4 and GeCl2. The former represents the second example of a structurally characterized neutral octahedrally coordinated germanium compound. Reaction of dilithiated 1 with GeCl2 does not lead to the expected ClGe(+2) complex but affords the novel dimeric germylene 5, whereas similar reaction using SnCl2 furnishes the monomeric stannylene (ClSn(+2) complex) 2 and elemental tin due to the higher oxidation potential of Sn(+2). Unexpectedly, a similar redox reaction of dilithiated 1 with PbCl2 furnishes the first air- and water-stable lithium 1,2-diketoimine,enolate 7 and elemental lead. Compound 7 is tetrameric in the solid state and consists of a strongly distorted Li4O4 cubic core with trigonal-bipyramidal coordinated Li+ ions. [source]