Search results for "aqueous solution"
showing 10 items of 1610 documents
Photocatalytic oxidation of cyanide in aqueous TiO2 suspensions irradiated by sunlight in mild and strong oxidant conditions
1999
Abstract The photocatalytic oxidation of free cyanide ions was carried out in aqueous aerated suspensions containing polycrystalline TiO2 (anatase) irradiated by sunlight. The influence of the presence of an organic compound (phenol) or of a strong oxidant (H2O2) on the photoprocess was also studied. The dependence of cyanide photo-oxidation rate on the following parameters: (1) cyanide concentration; (2) catalyst amount; and (3) phenol concentration was investigated. At the used experimental conditions, the kinetics of cyanide photo-oxidation is independent of the initial cyanide concentration and of the catalyst amount while it is affected by the phenol concentration and by the presence o…
ChemInform Abstract: 1,4-Regioselective Iodofunctionalizations of 1,3-Butadiene.
1989
1,3-Butadiene (I) is treated with a iodonium tetrafluoroborate in the presence of HBF4 and aqueous acetonitrile (II) or benzene (IV), yielding the 1,4-adducts (III) or (V).
Introduction of a luminescent sensor for tracking trace levels of hydrazine in insect pollinated cropland flowers
2021
In recent years the excessive use of hydazine containing chemical pesticides and insecticides in farming practices is well pronounced, which directly or indirectly impart a great threat towards the total environment. Considering the above fact we are motivated to introduce a new, efficient and simple chemodosimeter (NCD) based on a carbazole-naphthalimide framework to recognize and estimate the mutagenic hydrazine within several affected cropland flowers. Probe NCD can detect hydrazine in a nanomolar range (65 nM or 2 ppb) in the presence of other metal ions, anions and amines, which gives it not only great potential but also makes it selective and sensitive. The sensing mechanism is confir…
Special Calixarenes by Directed Syntheses
1997
The synthesis of special calixarenes and calixarene-like macrocyclic compounds via stepwise procedures and fragment condensation is reviewed. Among the compounds available are exo- and endo-calixarenes consisting of different phenolic units, having bridges other than methylene or showing inherent chirality (Cn-symmetry). Macrobi- and -tricyclic molecules such as bridged calixarenes, double calixarenes, bicyclocalixarenes and annelated calixarenes are also described. Single crystal X-ray structures are reported for several compounds. Some properties like conformational barriers, pKa values or the ability to complex metal ions are discussed, showing the potential of these compounds which may …
Selective Cobalt over Nickel separation using neat and confined ionic liquids
2020
International audience; Task Specific Ionic Liquids (TSILs) generated by association between tetraalkylammonium cations and coordinating anions such as dicyanamide (Dca-) and thiocyanate (SCN-) were used for the selective separation of Ni(II) over Co(II). SCN-based TSIL presents higher extraction efficiency than the Dca-based one towards Co(II) (E = 85.4 % vs 54.6 %) and Ni (II) (E = 22 % vs 0.5%) but lower separation factors (βCo/Ni = 21 vs 239). Interestingly, extraction of Co(II) and Ni(II) in Dca-based TSIL can be enhanced using salts with chaotropic anions such as NaNO3 (E > 90 % for Co(II) and E = 85% for Ni(II)). The use of NaCl allows, moreover, the efficient separation of both ions…
Optimized Continuous Application of Hyperpolarized Xenon to Liquids
2018
International audience; In recent years, NMR with hyperpolarized (HP) xenon inside functionalized host structures (e.g. cryptophanes) have become a potential candidate for the direct observation of metabolic processes (i.e. molecular imaging). A critical issue for real applications is the dissolution of the HP-gas in the liquid which contains the host. In this work, we present recent developments for an improved and controlled dissolution of HP-Xe in liquids using hollow fiber membranes and different compressor systems. The designed apparatus consists of a compressor and a membrane unit. The compressor provides HP-129 Xe continuously at small adjustable pressures and in a polarization-prese…
Electrocatalytic properties of manganese and cobalt polyporphine films toward oxygen reduction reaction
2018
International audience; Novel member of polymetalloporphines, namely manganese polymetalloporphine of type I (pMnP-I) obtained by ion exchange from magnesium polyporphine of type I (pMgP-I) is reported for the first time and compared to its cobalt analogue (pCoP-I). Both polymer films have been obtained via two-step procedure: demetaladon of the pMgP-I electrode film via its exposure to trifluoroacetic acid solution, resulting in formation of the metal-free polyporphine of type I (pH(2)P-I) followed by electrochemically induced incorporation of Co or Mn ions from the acetonitrile solution of cobalt and manganese perchlorates. A further oxidative transformation of pCoP-I, polymer films has l…
Dimerization of Copper Octacarboxyphthalocyanine in Aqueous Solutions
2005
Spectral absorption UV-Vis investigations on association of copper(II) octacarboxyphthalocyanine in aqueous solutions are reported. In 5.0x10-7-5.0x10-5 mol/dm3 concentration range monomers and dimers are mainly present. The calculated dimerization constant 106dm3/mol at 25°C and the hypsochromic spectral shift for the dimer 1164 cm-1 (688 nm_ 637 nm) indicate a stack-like association of molecules and suggestpi-pi interactions between Pc macrocycles in dimer and higher aggregates, in contrast to hydrogen bonding between carboxylic groups of adjacent Pc molecules.
Large Magnetic Polyoxometalates Containing the Cobalt Cubane ‘[CoIIICo3II(OH)3(H2O)6–m(PW9O34)]3− (m = 3 or 5) as a Subunit
2018
A synthetic procedure is presented to construct new magnetic polyoxometalates (POMs) containing one or two subunits of ‘[CoIIICo3II(OH)3(H2O)6−m(PW9O34)]3−' (m = 3 or 5). The substitution of the water ligands present in these subunits by oxo or hydroxo ligands belonging to other POM fragments, gives rise to four, larger POM anions: [Co7(OH)6(H2O)6(PW9O34)2]9− (2), [Co7(OH)6(H2O)4(PW9O34)2]n9n- (2′), [Co11(OH)5(H2O)5(W6O24)(PW9O34)3]22− (3) and [{Co4(OH)3(H2O)(PW9O34)}2{K⊂(H2W12O41)2}{Co(H2O)4}2]17− (4). The crystal structures, magnetic characterization and stabilities in aqueous solutions of these POM derivatives are also presented.
A Simple Complex on the Verge of Breakdown: Isolation of the Elusive Cyanoformate Ion
2014
Cyanide Hitches a Ride Cyanide is a by-product of the biosynthesis of ethylene in plants and it has been somewhat puzzling how the ion is safely removed before it can shut down enzymatic pathways by coordination to catalytic iron centers. A proposed mechanism has implicated the cyanoformate ion—essentially, a weak adduct of cyanide and carbon dioxide—as the initial product, although its lifetime was uncertain. Murphy et al. (p. 75 ; see the Perspective by Alabugin and Mohamed ) crystallized this previously elusive adduct and found that its solution-phase stability varies inversely with the dielectric properties of the medium. The results bolster a picture in which the adduct shuttles the cy…