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991.
Xifra R Ribas X Llobet A Poater A Duran M Solà M Stack TD Benet-Buchholz J Donnadieu B Mahía J Parella T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(17):5146-5156
A family of highly stable organometallic Cu(III) complexes with monoanionic triazamacrocyclic ligands (L(i)) with general formula [CuL(i)]+ have been prepared and isolated, and their structural, spectroscopic, and redox properties thoroughly investigated. The HL(i) ligands have been designed in order to understand and quantify the electronic effects exerted by electron donor and electron-withdrawing groups on either the aromatic ring or the central secondary amine or on both. In the solid state the Cu(III) complexes were mainly characterized by single-crystal X-ray diffraction analysis, whereas in solution their structural characterization was mainly based on 1H NMR spectroscopy given the diamagnetic nature of the d(8) square-planar Cu(III) complexes. Cyclic voltammetry together with 1H NMR and UV/Vis spectroscopy have allowed us to quantify the electronic effects exerted by the ligands on the Cu(III) metal center. A theoretical analysis of this family of Cu(III) complexes has also been undertaken by DFT calculations to gain a deeper insight into the electronic structure of these complexes, which has in turn allowed a greater understanding of the nature of the UV/Vis transitions as well as the molecular orbitals involved. 相似文献
992.
Cirilli R Ferretti R Gallinella B La Torre F La Regina G Silvestri R 《Journal of separation science》2005,28(7):627-634
The enantiomeric separation of a series of imidazole analogues of Fluoxetine and Miconazole endowed with potent antifungal activity was performed using cellulose tris(4-methylbenzoate) (Chiralcel OJ) and cellulose tris(3,5-dimethylphenylcarbamate) (Chiralcel OD) as chiral stationary phases. Binary mixtures of n-hexane and alcohol as well as pure alcohols (ethanol or 2-propanol) were used as eluents. The enantiomer elution order was monitored by chiroptical detectors based on on-line optical rotation and circular dichroism measurements. For some of the compounds studied very high enantioseparation factor values (alpha > 7) on Chiralcel OJ CSP were observed. In order to study the chiroptical characteristics of the two most biologically active compounds, chromatographic resolutions were carried out on a semipreparative scale. Assignment of the absolute configuration was empirically established by comparing the CD spectra of the separated enantiomers with those obtained from the enantiomers of Miconazole. 相似文献
993.
A gas chromatographic investigation of the steam distilled oil of the herb of Artemisia vulgaris led to the identification of 21 irregular monoterpenes of non-head-to-tail isoprenoid skeleton. The spectral data of some of these compounds are discussed. The structures of eight new irregular monoterpenes are given. 相似文献
994.
Bruno Zimmermann 《Monatshefte für Mathematik》1987,104(3):247-253
LetG be a group andK(G, 1) an Eilenberg—MacLane space, i.e. 1(K(G,1))G,
i
(K(G,1))=0,i1. We give a purely algebraic proof that the second homology groupH
2(G)=H
2(G,)H
2(K(G,1)) is isomorphic to the group of stable equivalence classes of continuous mapsFK(G,1) inducing surjections on fundamental groups (resp. surjections, whereF{F
g=closed orientable surface of genusg,g}. As a corollary we obtain an algebraic proof of the well-known isomorphismH
2(G)2(K(G,1)) (2-dimensional bordism group). 相似文献
995.
We examine quasi-regular singularities that take the form of invariant two-dimensional null planes in Minkowski space-time, thus extending earlier studies of conical singularities based on timelike and spacelike planes. The result is described in terms of a deficit parameter. We also examine the form of the Riemann curvature tensor at the singularity. 相似文献
996.
Halochromic Molecules. Synthesis and Acidobasic Behaviour of Substituted 3′,6′-Bis(dimethylamino)-spiro [5H-imidazo [2,1-α]isoindolin-5,9′-xanthenes] Substituted 3′,6′-Bis (dimethylamino)-spiro [5H-imidazo [2, 1-α]isoindolin-5,9′-xanthenes] are prepared and their 1H-NMR. spectra are discussed. An investigation of the complex protonation equilibria is made by stopped flow kinetic and spectrophotometric methods. pK values are determined and the results are discussed. 相似文献
997.
Franco Bonino Mario Lazzari Bruno Scrosati 《Journal of Electroanalytical Chemistry》1978,93(2):117-125
The behaviour of positive electrodes based on silver polymolybdate (Ag2Mo2O7, Ag6Mo10O33) and polytungstates (Ag2W2O7, Ag2W4O13) in lithium-organic solvent batteries has been investigated. The performances of the lithium/silver oxosalt couples are given and the discharge processes are discussed. 相似文献
998.
A series of chiral aryl alkyl carbinols, dissolved in MBBA and other nematic solvents, induce cholesteric structures. The handedness of the induced mesophases and the twisting power of the dopant alcohols are studied by means of CD and Grandjean-Cano microscopic techniques. The investigation points out the possibility of obtaining information on the stereochemistry of the dopant by studying the characteristics of the induced helices.Two different types of H- bonds between alcohols and MBBA are discussed in connection with a possible model of induction. 相似文献
999.
1000.
Anna Lisa Piccinelli Mariano Barrios Chica Bruno Pagano Vincenzo Barone 《Tetrahedron》2005,61(34):8206-8211
For the first time, the tautomeric pairs of clusianone and 7-epi-clusianone were isolated from the same source, Clusia torresii fruits. An extensive NMR spectroscopic study is described to establish 1H and 13C chemical shift assignments and the C-7 relative configuration of these epimers and to clarify contradictory NMR spectroscopic data previously reported. Quantum mechanical computations than pointed out the relationship between indirect coupling constants and the equilibrium between the B-ring chair and twist-boat forms of the bicyclo-[3.3.1.]-nonane system. Clusianone, 7-epi-clusianone and polyisoprenylated benzophenones 18,19-dihydroxyclusianone, propolone A and nemorosone were screened for their activity against HIV infection in C8166 cells. All compounds inhibited infection with selectivity index values ranging from 2.25 to 15.6. Only clusianone derivatives inhibited infection by binding to viral protein gp120 and prevented its interaction with cellular receptor CD4 as detected by ELISA using recombinant proteins. 相似文献