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1.
Grzegorz Schroeder Bogumi
Brzezinski Dariusz Pod
bski Eugeniusz Grech 《Journal of Molecular Structure》1997,416(1-3):11-19
Deprotonation of 5,10,15,20-tetrakis(pentafluorophenyl)-21-H, 23-H-porphyrin (PhF5PorH2) by various bases has been studied by 1H NMR and kinetic methods. The kinetic parameters in acetonitrile were defined for proton transfer reactions yielding [NH]+ protonated bases and [NHN]− anions with intramolecular hydrogen-bonded chains. 相似文献
2.
Bogumił Łaszkiewicz 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(2):421-432
The reaction mechanism of phosphorous acid and poly(vinyl alcohol) is presented. It has been found that there during this reaction mono- and diesters are formed in which most of the acid radicals are in the phosphonic form. To confirm the presence of this form in the product obtained, reactions with diethyleneamine and chloral have been carried out as characteristic tests for phosphonic groups. The occurrence of C—P bonds resistant to hydrolysis has been also found in the reaction product. 相似文献
3.
Joanna Ronowicz Bogumiła Kupcewicz Elżbieta Budzisz 《Central European Journal of Chemistry》2014,12(6):700-710
In this study, antioxidant properties of commercial green teas and dietary supplements containing Camellia sinensis extracts were evaluated. Extracts were examined using two antioxidant assays (DPPH· radical method and ABTS·+ cation radical method). A Folin-Ciocalteu assay was used to evaluate the total polyphenol content in the extracts. In order to compare and characterize the investigated Camellia sinensis extracts, chemometric techniques based on fingerprint chromatograms, antioxidant activity and total polyphenol content were applied. Application of chemometric methods allowed for reduction of multidimensionality of the data set and grouped the samples into differentiable clusters. The relationship between the antioxidant activity and total polyphenol content was also assessed. The results indicated that extracts with the higher polyphenolic content exhibited the stronger antiradical activity against both DPPH· radicals and ABTS·+ cation radicals. The multivariate calibration technique (such as a tree regression algorithm) can be a useful tool for rapid determining the antioxidant activity of a herbal product based on its fingerprint chromatogram 相似文献
4.
Skrodzka E Łapa A Linde BB Rosenfeld E 《The Journal of the Acoustical Society of America》2011,130(4):2186-2194
Similarities and differences in vibrational behavior of two guitars having a symmetric Torres bracing pattern and an asymmetric pattern forming a lattice on a soundboard are investigated by means of the modal analysis technique and laser Doppler vibrometry (LDV) measurements. Instruments are investigated before and after a bridge and strings assembling (i.e., they are incomplete or complete). The bracing pattern and the absence/presence of the bridge and strings have some effect on modal frequencies and mode shapes. The bracing pattern does not affect the sequence of at least first three low frequency mode shapes of incomplete/complete instruments but affects their modal frequencies. Depending on frequency, the bridge behaves either as a rigid or a flexible structure. 相似文献
5.
A series of five chloride coordination compounds of diethyl (pyridin-4-ylmethyl)phosphate (4-pmOpe) ligand, i.e. [CuCl2(4-pmOpe)2], [NiCl2(4-pmOpe)4], [CoCl2(4-pmOpe)], [ZnCl2(4-pmOpe)2], and [CdCl2(4-pmOpe)2], was prepared and studied. Stoichiometry and stereochemistry of the compounds was confirmed by spectroscopic and magnetic
studies as well as by elemental analyses. The 4-pmOpe ligand has a capacity to coordinate to metal ions by means of phosphoryl
oxygen and/or nitrogen of pyridine atoms. In Cu(II), Ni(II), and Zn(II) compounds, 4-pmOpe adopts the monodentate coordination
mode, bonding metal centers through the pyridine nitrogen atom only. On the contrary, in Co(II) and Cd(II) compounds, 4-pmOpe
acts as N,O-bridging ligand forming polynuclear structures. Magnetic studies (1.8–300 K) indicate mononuclear structure of the Co(II)
and Ni(II) compounds and suggest existence of a very weak exchange coupling between metal centers in crystal lattice. 相似文献
6.
An analytic function f in the unit disk
D :={z ∈ ? : |z| < 1}, standardly normalized, is called close-to-convex with respect to the Koebe function
k(z) := z/(1−z)2, z ∈ D if there exists δ∈(-π/2,π/2) such that
Re{eiδ(1−z)2f′(z)} > 0, ∈ D. For the class C(k) of all close-to-convex functions with respect to k, related to the class of functions convex in the positive direction of the imaginary axis, the Fekete-Szegö problem is studied. 相似文献
7.
Tomasz Pospieszny Marta Pakiet Iwona Kowalczyk Bogumił Brycki 《Supramolecular chemistry》2017,29(2):81-93
New dimers have been obtained from propargyl ester of bile acids and α,α′-diazide-m-xylene by intermolecular 1,3-dipolar cycloaddition. These compounds have been used as ligands to form intermolecular hydrogen bonds with various aromatic acids. The structures of all products were confirmed by spectroscopic (1H NMR, 13C NMR and FT-IR) analysis, mass spectrometry (ESI, MALDI) and PM5 semiempirical methods. 相似文献
8.
Bogumi?a KupcewiczMagdalena Grazul Ingo-Peter LorenzPeter Mayer Elzbieta Budzisz 《Polyhedron》2011,30(6):1177-1184
Three new Zn(II) complexes containing the ligands 5-amino-8-methyl-4H-chromen-4-one (1), 6- or 7-amino-2-phenyl-4H-chromen-4-one (2, 3) were prepared. The new synthesised compounds were characterised by IR, 1H NMR and MS spectroscopy. The crystal structure of complex 4 was determined with the use X-ray diffraction. The Zn(II) centre of 4 is linked by two chlorido and two N-bound aminochromone ligands, 1, in a strongly distorted tetrahedral configuration with the dissymetric point group C2. The protonation constants of the ligands 1, 2 and 3 corresponded to 3.68, 3.88 and 6.83, respectively. The stability constants of the Zn(II) complexes were calculated from the potentiometric titration data. The complexes were found to have the formulae ML and ML2 for ligands 1 and 2, and ML for ligand 3. Fluorescence spectroscopic properties were also studied; the strongest fluorescence in solution was exhibited by complex 6. 相似文献
9.
10.
The influence of TiOSO4 and free sulphuric acid concentrations in the starting solution on the degree of titanyl sulphate conversion to hydrated
titanium dioxide and post-hydrolytic sulphuric acid was studied. Titanyl sulphate solution, an intermediate product in the
commercial preparation of titanium dioxide pigments by sulphate route, was used. It was found that the degree of hydrolysis
markedly depends on the studied parameters. The lower was the content of TiOSO4 in the starting solution, the higher conversion was achieved. The degree of hydrolysis at the final stage varied between
81 % (420 g TiOSO4 dm−3, 216 g H2SO4 dm−3) and 92 % (300 g TiOSO4 dm−3, 216 g H2SO4 dm−3). The same relation was obtained when changing the concentration of free H2SO4 in the starting solution. The degree of hydrolysis at the final stage varied between 49 % (261 g H2SO4 dm−3, 340 g TiOSO4 dm−3) and 96 % (136 g H2SO4 dm−3, 340 g TiOSO4 dm−3). The particle size of the obtained hydrated titanium dioxide (HTD) also depends on the initial solution composition.
Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May
2007. 相似文献