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11.
Bianchini C Giambastiani G Laschi F Mariani P Vacca A Vizza F Zanello P 《Organic & biomolecular chemistry》2003,1(5):879-886
A new potentially hexadentate tetraazamacrocycle based on the cyclen skeleton has been synthesized and fully characterized. The macrocycle 4,10-dimethyl-1,4,7,10-tetraazacyclododecane-1,7-bis(methanephosphonic acid monoethyl ester) dipotassium salt (Me2DO2PME) contains mutually trans monoethyl ester phosphonate acid substituents on two nitrogen atoms, and trans methyl substituents on the other two nitrogen atoms. The protonation constants of this macrocycle and the stability constants of its complexes with Cu2+, Zn2+, Gd3+ and Ca2+ ions have been determined by pH potentiometric titrations. The protonation sequence of the macrocycle has been studied by 1H, 31P[1H] and 13C[1H] NMR spectroscopy: the first and second protonation steps take place at the methyl-substituted nitrogen atoms, while the third protonation involves one oxygen from a phosphonate group. Upon protonation, all the CH2 ring protons become magnetically inequivalent on the NMR time scale due to a slow conformational rearrangement, most likely occasioned by the formation of multiple hydrogen bonds within the macrocyclic ring. Me2DOPM forms neutral, mononuclear complexes with all the metals investigated. The presence of hydroxo complexes was observed for Ca2+ and Zn2+ at high pH values. Structural information on the neutral complex [Cu(Me2DO2PME)] has been obtained by a solution X-Band EPR study. It is proposed that Me2DO2PME binds Cu2+ in a distorted octahedral structure using all of its donor atoms, i.e. the four nitrogen atoms and the two phosphonate oxygen atoms. The redox chemistry of [Cu(Me2DO2PME)] in dimethyl sulfoxide and water has been studied by electrochemical measurements. Cyclic voltammetry in DMSO shows the complex to undergo a quasireversible one-electron reduction step leading to an unstable CuI species. 相似文献
12.
Paul S. Pregosin S. N. Sze Piero Salvadori Raffaello Lazzaroni 《Helvetica chimica acta》1977,60(8):2514-2521
13C- and 195Pt-NMR. spectra for the complexes trans-PtCl2(amine)(CH2?CH2) have been measured. For amine = (S)-N-methyl-α-methylbenzylamine the two diastereomers present may be distinguished from the values 3J(Pt,C). The 195Pt-chemical shift is shown to be sensitive to subtle differences stemming from intramolecular non-bonded interactions. 相似文献
13.
Piero Zanello Renato Seeber Bruno Crociani Marino Nicolini 《Transition Metal Chemistry》1980,5(1):45-48
Summary The electrochemical behaviour of a series of cationic platinum(II) isocyanide complexes has been studied in acetonitrile. All the tested compounds are oxidized at a platinum electrode via a two-electron process and reduced at a platinum or mercury electrode via two successive one-electron steps. The anodic step involves the formation of platinum(IV) complexes. The main reduction product formed in correspondence to the first cathodic process is a stable dimer platinum(I) containing bridging isocyanide ligands. Platinum(0) species are formed in the subsequent reduction step. 相似文献
14.
Vincenzo Bertini Angela De Munno Paolo Pelosi Piero Pino 《Journal of heterocyclic chemistry》1968,5(5):621-624
Cycloaddition of fulminic acid to 1-butyn-3-ol gave a mixture of 5-α-hydroxyethylisoxazole (I) and 4-α-hydroxyethylisoxazole (II) in the ratio 9:1. By the dehydration of 1, 5-vinylisoxazole (III) was obtained. Compound III has also been prepared by cyclization of 4-penten-2-ynal as well as its diethylacetal with hydroxylamine hydrochloride; in both instances no isomers have been obtained. Compound III spontaneously polymerizes even at room temperature yielding a polymer still containing isoxazole rings. 相似文献
15.
Piero Pino Felix Oldani Giambattista Consiglio 《Journal of organometallic chemistry》1983,250(1):491-497
In the hydroformylation of ethylene with approximately equimolar H2/D2 mixtures and Rh4(CO)12 or Co2(CO)8 as the catalyst precursor about 50% of propionaldehyde-d1 was formed. The propionaldehyde-d0/d2 ratio was ~ 3 for rhodium and ~ 2.6 for the cobalt catalyst. On the basis of the results and assuming that there is no rapid M(H)2/M(D)2 scrambling, activation of hydrogen through M(H)2 or M(H)2(olefin) complexes can be excluded. 相似文献
16.
Mario Bianchi Ugo Matteoli Piero Frediani Gloria Menchi Franco Piacenti 《Journal of organometallic chemistry》1982,236(3):375-380
Hydrogen transfer from racemic alcohols to prochiral ketones in the presence of H4Ru4(CO)8[(?)-DIOP]2 has been examined. The enantiomer-discrimination is influenced by the structure of the reactants, temperature and the excess of phosphine present. 相似文献
17.
Onida B Borello L Busco C Ugliengo P Goto Y Inagaki S Garrone E 《The journal of physical chemistry. B》2005,109(24):11961-11966
Joint IR and computational results allow a detailed characterization of the surface properties of a mesoporous benzene-silica hybrid material with crystal-like wall structure. After outgassing at 450 degrees C, hydroxyl species mainly consist of noninteracting silanols, with both O-H and Si-O stretching modes at lower frequencies than those of SiOH in silica. Interaction with several probe molecules, followed both by experiment and calculus, shows that the aryl group in the coordination sphere of Si imparts a lesser acidity with respect to the isolated silanol in silica. In contrast, adsorption isotherms indicate that the interaction with acetone is stronger with benzene-silica than with silica: this is interpreted in terms of secondary interactions taking place between the slightly acidic CH in acetone and the electronic cloud in benzene-like rings. This suggests that both the inorganic component and the organic one play a role in dictating the surface behavior. 相似文献
18.
The reaction of thiazolidines 2 and 7 with borane was investigated. It gave N-methylcysteamines 3 and 8 through thiazolidine ring opening. Sodium borohydride and lithium aluminum hydride were ineffective. 相似文献
19.
Guido Audisio Maria Grassi Piero Traldi Sergio Daolio 《Journal of mass spectrometry : JMS》1985,20(5):327-330
The positive ion chemical ionization (CI (isobutane)), negative ion chemical ionization (NICI) electron attachment (CH4, He) and NICI (OH?) spectra of the title compounds have been studied in detail with the aid of deuterium-labelled derivatives. The obtained results show that under CI conditions the stereospecificity is retained. Interesting correlations with the condensed phase epimerization yields are emphasized. 相似文献
20.
Caffeic acid phenethyl ester (CAPE), an active component of propolis from honeybee hives, is known to have antimitogenic, anticarcinogenic, antinflammatory, and immunomodulatory properties. The paper describes a rapid and simple liquid chromatography-electrospray ionisation mass spectrometry method for qualitative and quantitative determination of CAPE. The chromatographic separation was performed with a Luna RP-C18 column using a water-acetonitrile linear gradient. The method was linear over a 0.125-80 ng/mL range (LOD = 62.5 pg/mL). The method was applied for the quantitation of caffeic acid phenethyl ester in crude propolis samples, which were analysed directly after extraction with ethyl acetate solution. 相似文献