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121.
The fluorescence quenching of the doubly charged quinine cation by Fe++, Ag+, and Br? was studied in the presence and absence of polyvinylsulfonate (PVS). The quenching by cationic species was greatly enhanced by PVS at low polyion concentrations; at higher concentrations of PVS, the fluorescence intensity increased owing to displacement of the quinine cations from the polyion domain. Quenching of quinine fluorescence by Br? was repressed by PVS. Interpretation of the data with the use of Fe++ as the quenching agent led to “effective concentrations” of counterions in the polyion domain similar to those calculated from the catalysis of the redox reaction of Co(NH3)5Cl++ with Fe++. This may indicate that the reagent ions are not rigidly bound to the polyion chain, since such binding would affect differently processes with high and low activation energies. The Stern-Volmer constant for self-quenching of the quinine fluorescence can also be obtained from fluorescence intensity data in PVS solution. 相似文献
122.
The Cotton effect of olefins in the pimaric acid series is discussed. The contribution of the vinyl group is important when it is near the endocyclic double bond and becomes negligible when the two double bonds are far apart. 相似文献
123.
Charles Z. Hotz Peter Kovacic Issam A. Khoury 《Journal of polymer science. Part A, Polymer chemistry》1983,21(9):2617-2628
Although polymerization of 2,5-dibromothiophene via coupling of the Grignard reagent with organonickel salts was reported in two earlier communications, a detailed examination of reaction variables was not done. This report provides results from variation in the following: time, amount of magnesium, amount of iodine, dilution, and variation in the halide of the monomer. The highest yield was obtained for reactions with 1:1 molar ratio of monomer to magnesium in more concentrated solutions of tetrahydrofuran for a reaction time of 4 h. For variation in the halogen of the monomer the following yield sequence was obtained: I > Br > Cl. The results are compared with the corresponding benzenoid system investigated by Yamamoto. In addition, polymerization studies were carried out with other brominated thiophene monomers. Use of an organic promoter (cis-1,4-dichloro-2-butene) in place of a nickel salt proved successful in the generation of poly(2,5-thienylene). 相似文献
124.
Beraldo Heloisa Kaisner Susan B. Turner Jennifer D. Billeh Issam S. Ives Janeice S. West Douglas X. 《Transition Metal Chemistry》1997,22(5):459-464
Copper(II) and nickel(II) complexes of phenylglyoxal and phenylpropane-1,2-dione bis{N(3)-methyl-, bis{N(3)-dimethyl-, bis{piperidylthiosemicarbazone} have been prepared and studied spectroscopically. The six bis(thiosemicarbazones) have been characterized by their melting points, as well as i.r., electronic and 1H-n.m.r. spectra. The four-coordinate copper(II) complexes have been studied by e.s.r. spectroscopy, and the copper(II) and nickel(II) complexes by spectroscopic techniques mentioned above. Upon formation of these complexes, the loss of protons from each thiosemicarbazone moiety occurs, and the bis(thiosemicarbazones) coordinate to the metal centres as dianionic, tetradentate N2S2 ligands. 相似文献
125.
West Douglas X. Billeh Issam S. Jasinski Jerry P. Jasinski John M. Butcher Ray J. 《Transition Metal Chemistry》1998,23(3):209-214
2-Formyl-, 2-acetyl- and 2-benzoylpyridine N(4)-cyclohexylsemicarbazone and N(4)-cyclohexylthiosemicarbazone complexes of cobalt(II, III), nickel(II) and copper(II) have been prepared and characterized
by molar conductivities, magnetic susceptibilities and spectroscopic techniques. For many of the complexes, coordination is
by the neutral ligand, the main exceptions being the cobalt(III) complexes of the three thiosemicarbazones and three of the
benzoylpyridine derivatives. Thus, bonding is via the pyridyl nitrogen, azomethine nitrogen and thione/thiolato sulfur. The five-coordinate copper(II) complex of 2-acetylpyridine
N(4)-cyclohexylthiosemicarbazone, [Cu(HAc4CHex)Cl2], approaches square pyramidal stereochemistry with the basal Cu—Cl bond significantly shorter than the apical Cu—Cl bond.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
126.
Issam M. Gabr Hala A. El-Asmy Mohamed S. Emmam Sahar I. Mostafa 《Transition Metal Chemistry》2009,34(4):409-418
Synthetic procedures are described that allow access to the new complexes cis-[Mo2O5(apc)2], cis-[WO2(apc)2], trans-[UO2(apc)2], [Ru(apc)2(H2O)2], [Ru(PPh3)2(apc)2], [Rh(apc)3], [Rh(PPh3)2(apc)2]ClO4, [M(apc)2], [M(PPh3)2(apc)]Cl, [M(bpy)(apc)]Cl (M(II) = Pd, Pt), [Pd(bpy)(apc)Cl], [Ag(apc)(H2O)2] and [Ir(bpy)(Hapc)2]Cl3, where Hapc, is 3-aminopyrazine-2-carboxylic acid. These complexes were characterized by physico-chemical and spectroscopic
techniques. Both Hapc and several of its complexes display significant anticancer activity against Ehrlich ascites tumour cells (EAC) in albino mice. 相似文献
127.
Douglas X. West Issam S. Billeh Gordon A. Bain Jesús Valdés-Martínez Klaus H. Ebert Simón Hernández-Ortega 《Transition Metal Chemistry》1996,21(6):573-582
Summary 2-Acetylpyridine N(4)-dihexyl- and N(4)-dicyclohexylthiosemicarbazone, HAc4DHex and HAc4DCHex, respectively, and FeIII, CoII, CoIII, NiII, CuII and ZnII complexes have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. For many of the complexes, loss of the N(2)H hydrogen occurs, and the ligands coordinate to the metal centres as NNS monoanionic, tridentate ligands, e.g., [M(NNS)X] (M = CoII, NiII, CuII, NNS = Ac4DHex or Ac4DCHex and X = Cl or Br), [Fe(NNS)2]ClO4, [Co(NNS)2]BF4, [Cu(NNS)NO3] and [Zn(NNS)OAc]. ZnII ion is also chelated by neutral ligands in [Zn(HNNS)X2] (X = Cl, Br). In addition, [Ni(Ac4DHex)-(HAc4DHex)]X (X = BF4, ClO4) and [Ni(HAc4DCHex)2]-(BF4)2 are reported where the neutral thiosemicarbazone is coordinated via the pyridyl nitrogen, azomethine nitrogen and thione sulfur. Crystal structure determinations of HAc4DCHex and [Cu(Ac4DHex)Br] show the former to contain the bifurcated hydrogen bonded form and the latter to be planar with no significant interaction between neighbouring centres. 相似文献
128.
Dissociation constants of some polyprotic acids and bases are determined from spectrophotometric and reversed-phase high performance liquid chromatographic data. A general equation relating additive properties of acids and bases to the pH of the solution is used for this purpose. The method is tested by applying it to the calculation of overlapping pKas without the prerequisite of measuring the limiting values of the property for the individual species that result from the dissociation of the solute. The possibility of applying the same method to hyperpolarizability measurements is pointed out, and a procedure, based on the general equation, for obtaining the activity coefficients of the ionic species as a function of the ionic strength is also suggested. 相似文献
129.
In the present Note, we propose an estimator of Shanonn?s entropy based on smooth estimators of quantile density. The consistency and asymptotic normality of the proposed estimates are obtained. 相似文献