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331.
Clinio Locatelli Francesco Fagioli Tibor Garai Corrado Bighi Roberto Vecchietti 《Analytica chimica acta》1988
Second-harmonic phase-selective a.c. voltammetry and second-harmonic a.c. anodic stripping voltammetry are shown to be particularly suitable for simultaneous determinations of elements having very close half-wave potentials (differences of <50 mV). The technique are applied to real matrices. Samples of standard materials BCS 207/2 Gunmetal, SRM 631 SPectrographic Zinc Spelter and SRM 899 (Nickel-base High-temperature Alloy) were digested with a sulphuric acid/nitric acid mixture; after dissolution, the samples were taken up in hydrochloric acid. After adjustment to 1 mol l?1 HCl, the solutions were used directly for voltammetric measurements of Pb(II)/Sn (II), Sb(III)/Bi(III), Pb(II)/Tl(I) and In(III)/Cd(II) as appropriate. The confidence intervals of the experimental data were in agreement with the certified values for each element. Both the accuracy, expressed as percentage error, and precision, expressed as relative standard deviation, were better than 5%. The standard addition technique was found to improve the resolution of the a.c. voltammetric peaks even in the case of severe overlapping. 相似文献
332.
Yurij A. Simonov Tadeush I. Malinowskii Eduard V. Ganin Sergei A. Kotlyar Gabriele Bocelli Gianluca Calestani Corrado Rizzoli 《Journal of inclusion phenomena and macrocyclic chemistry》1990,8(3):349-361
The crystal structure of two complexes of the isomerscis-syn-cis (isomer A) andcis-anti-cis (isomer B) of dicyclohexano-18-crown-6 with 4-methylbenzenesulfamide have been determined by X-ray single crystal diffraction methods. The two structures have been solved by direct methods and refined to agreement values of 0.067 and 0.038 for isomers A and B respectively. The first isomer forms an inclusion compound with a host/guest ratio of 1 : I; the second one of I:2. The amino groups of the guest molecules are connected by N-H...O hydrogen bonds with oxygen atoms of the polyether molecules. The methyl groups of 4-methylbenzenesulfamide do not form hydrogen bonds.[/p]The host-guest interactions in the molecular complexes, the reciprocal influence of the two molecules on their conformation and the intermolecular contacts between the molecules in the crystal are discussed. 相似文献
333.
Di Nicola C Galindo A Hanna JV Marchetti F Pettinari C Pettinari R Rivarola E Skelton BW White AH 《Inorganic chemistry》2005,44(9):3094-3102
Seven novel R2Sn(IV)-oxydiacetate (oda) and -iminodiacetate (ida) compounds of the form [R2Sn(oda)(H2O)]2 (R = Me, nBu, and Ph) (1-3), [(R2SnCl)2(oda)(H2O)2]n (R = Et, iBu, and tBu) (4-6), and [Me2Sn(ida)(MeOH)]2 (7) have been synthesized and characterized by IR, 1H, 13C, and 119Sn NMR (solution), solid-state 119Sn CPMAS NMR, and (119m)Sn M?ssbauer spectroscopy. The crystal structure of [Me2Sn(oda)(H2O)]2, 1, shows it to be dinuclear (centrosymmetric), with two seven-coordinated tin atoms, bridged by one arm of the carboxylate group from each oda. By contrast, the crystal structure of [(Et2SnCl)2(oda)(H2O)2]n, 4, comprises a zigzag polymeric assembly containing a pair of different alternating subunits, {Et2SnCl(H2O)} and {Et2SnCl(H2O)(oda)}, which are connected by way of bridging oda carboxylates, thus giving seven-coordinate tin centers in both components. Finally, the structure of [Me2Sn(ida)(MeOH)]2, 7, also centrosymmetric dinuclear, is comprised of a pair of mononuclear units with seven-coordinate tin. The 119Sn solid-state CPMAS NMR and (119m)Sn Mossbauer suggest the presence of seven-coordinate Sn metal atoms in some derivatives and the existence of two different tin sites in the [(R2SnCl)2(oda)(H2O)2]n compounds. 相似文献
334.
Belicchi Marisa Ferrari Gasparri Giovanna Fava Pelizzi Corrado Tarasconi Pieralberto 《Transition Metal Chemistry》1985,10(8):295-299
Summary The reactions of Cu(NO3)2 · 3 H2O with 2- (2-thienyl)-1-(2-thienylmethyl)benzimidazole (L) and of CuCl2 · 2H2O with 2-(2-thienyl)benzimidazole (L) have been carried out. The crystal structure of two isolated complexes,(1) and(2), have been determined by single-crystal x-ray diffraction methods. Crystals of(1) are monoclinic, space groupP21
/c, witha=9.884(4),b=9.892(4),c=18.732(8) Å, =114.89(2)°,Z=2;R=0.068 for 1909 observed reflections. Crystals of (2) are orthorhombic, space groupPbcn, witha=14.835(1),b=8.193(1),c=20.493(1) Å,Z=4;R=0.086 for 415 observed reflections. In the complex (1) the copper co-ordination is tetragonal (compressed octahedral) and involves a nitrogen atom of the organic ligand [Cu-N 1.970(6) Å] and two oxygen atoms of the nitrate group [Cu-O 2.318(7) and 2.246(9) Å] which appears to coordinate nearly symmetrically to the metal; however it has unusually large thermal motion which suggests a fluxional behaviour. In the complex (2) the co-ordination is square planar and involves an imidazole nitrogen [Cu-N 1.95(3) Å] and a chlorine atom [Cu-Cl 2.27(1) Å]. A long interaction Cu-S=3.37(2) Å completes the co-ordination polyhedron to a very elongated distorted tetragonal bipyramid. In both compounds a thiophene ring is disordered. 相似文献
335.
Barbara Cardillo Carla Conti Elisabetta Giorgini Lucedio Greci Pierluigi Stipa Giorgio Tosi Corrado Rizzoli Paolo Sgarabotto Franco Ugozzoli 《Journal of heterocyclic chemistry》1992,29(5):1349-1355
2-Phenyl-3-phenylimino-3H-indole reacts with indole, 2-methylindole and 1,2-dimethylindole in the presence of stoichiometric trichloroacetic acid to form 1,2-dihydro-2-phenyl-2-(indol-3-yl-derivatives)-3-phenylimino-3H-indole, which during a longer period of time (16 hours) undergoes indolyl transposition to carbon-3 and elimination of aniline affording the 3,3′-bis-indolyls. In the case of 1,2-dimethylindole the intermediate coming from the indolyl migration may undergo a nucleophilic addition to carbon-2 of another molecule of indole; the new intermediate leads to the formation of 2-phenyl-3,3′-di-(1,2-dimethylindol-3-yl)-3H-indole by elimination of aniline and migration to carbon-3 of the second molecule of indole. By treatment with hydrochloric acid in refluxing ethanol, 1,2-dihydro-2-phenyl-2-(indol-3-yl-derivatives)-3-phenylimino-3H-indole afford to 3,3′-bis-indolyls and 1,2-dihydro-2-phenyl-2-(indol-3-yl-derivatives)-3H-indol-3-one (indoxyls). The crystal structure of 1,2-dihydro-2-phenyl-2-(indol-3-yl)-3-phenylimino-3H-indole is also reported. The latter compound does not give rearrangement products by acid treatment, only untreatable tarry material. 相似文献
336.
Laila Abdel-Rahman Luigi P. Battaglia Corrado Rizzoli Paolo Sgarabotto 《Journal of chemical crystallography》1995,25(10):629-632
The title compound was synthesized and characterized by conventional methods and its X-ray crystal structure was determined. The complex crystallizes in the monoclinic space group C2/c with eight formula units in a cell of dimensions:a=36.714(4),b=15.746(2),c=12.337(2) Å; =102.9(1)°. The structure is built up by alternate layers of octahedral [Ni(phen)3]2+ cations and perchlorate anions with water molecules which run in the direction of thea axis nearly parallel to thebc plane. 相似文献
337.
The generalized chain geometry over the local ring $K(\varepsilon ; \sigma)The generalized chain geometry over the local ring of twisted dual numbers, where K is a finite field, is interpreted as a divisible design obtained from an imprimitive group action. Its combinatorial properties
as well as a geometric model in 4-space are investigated.
Dedicated to Helmut M?urer on the occasion of his 70th birthday 相似文献
338.
Corrado Manara Vincenzo Marra Daniele Mundici 《Transactions of the American Mathematical Society》2007,359(4):1593-1604
Baker-Beynon duality theory yields a concrete representation of any finitely generated projective Abelian lattice-ordered group in terms of piecewise linear homogeneous functions with integer coefficients, defined over the support of a fan . A unimodular fan over determines a Schauder basis of : its elements are the minimal positive free generators of the pointwise ordered group of -linear support functions. Conversely, a Schauder basis of determines a unimodular fan over : its maximal cones are the domains of linearity of the elements of . The main purpose of this paper is to give various representation-free characterisations of Schauder bases. The latter, jointly with the De Concini-Procesi starring technique, will be used to give novel characterisations of finitely generated projective Abelian lattice ordered groups. For instance, is finitely generated projective iff it can be presented by a purely lattice-theoretical word.
339.
Alimelli A Filippini D Paolesse R Moretti S Ciolfi G D'Amico A Lundström I Di Natale C 《Analytica chimica acta》2007,597(1):103-112
The combination of computer monitors and webcams has been recently demonstrated to behave as a sort of spectrophotometer able to classify and recognize substances according to their light absorption and emission properties. This measurement technique is known as computer screen photoassisted technique (CSPT).In this paper, it is demonstrated for the first time and in the case of a complex sample such as red wine, that also quantification of integral parameters (colour indicators) and specific compounds (total anthocyanins and polyphenols) is possible through a multivariate analysis of CSPT fingerprints. Most of the properties of the method are due to the combination of light emission and absorption properties that are captured by the CSPT platform. Thanks to this combination, a CSPT fingerprint may contain a comparable amount of information with respect to standard spectrophotometers.Wine measurements were performed on intact samples without the intervention of chemical mediators. The regression models, built by Partial Least Squares, obtained errors of estimation of colour parameters, total polyphenols and anthocyanines that are comparable with those typical of the standard methods in use.Since computation functionalities, video capture and display are embedded in a steadily growing number of ubiquitously distributed equipments (from portable computers to cellular phones), these results indicate a viable methodology for low-cost and largely diffused analytical capabilities. 相似文献
340.
Di Nicola C Karabach YY Kirillov AM Monari M Pandolfo L Pettinari C Pombeiro AJ 《Inorganic chemistry》2007,46(1):221-230
Formation of the trinuclear triangular copper derivative [Cu3(mu3-OH)(mu-pz)3(EtCOO)2(H2O)] x H2O, 1b (Hpz = pyrazole), has been simply achieved by addition of Hpz to a water solution of Cu(EtCOO)2 x H2O and leaving the resulting solution to crystallize at ca. 12 degrees C. When the reaction and crystallization were carried out at a slightly higher temperature (18-22 degrees C), the compound [Cu3(mu3-OH)(mu-pz)3(EtCOO)2(H2O)], 1c, formed. Single-crystal X-ray molecular structure determinations show that both compounds have analogous trinuclear triangular structures, but very different supramolecular assemblies, due mainly, but not only, to the crystallization molecule of H2O in 1b. In particular, contrarily to the previously reported, strictly related, [Cu3(mu3-OH)(mu-pz)3(EtCOO)2(EtOH)], 1a, the propionate ions in 1b and 1c do not bridge different triangular units, whereas they are involved in intra- and intermolecular H-bonds, generating complex supramolecular 2-D MOFs. Compounds 1a and 1c act as remarkably active and selective catalysts or catalyst precursors for liquid biphasic (MeCN/H2O) peroxidative oxidation of cyclohexane and cyclopentane to the corresponding alcohols and ketones. 相似文献