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31.
Camporese D Riondato M Zampieri A Marchiò L Tapparo A Mazzi U 《Dalton transactions (Cambridge, England : 2003)》2006,(36):4343-4347
The synthesis, the characterization and the X-ray crystal structure of a novel tantalum(v) complex tris(1,2-dimethyl-3-hydroxy-4(1H)-pyridone)oxotantalum(v) [TaO(C7H8O2N)3] 1 is reported. Starting from the tantalum pentaethoxide a two-step reaction was carried out observing rigorous anhydrous conditions in methanol in the first step, while the insertion of the oxo group was achieved using water as oxygen donor in the second step. X-Ray diffraction analysis of a crystal of 1 obtained upon evaporation of an aqueous solution shows a seven-coordinate monomeric complex containing the [Ta=O]3+ core in the triclinic space group P1, a = 7.282(3), b = 14.055(5), c = 16.987(6) A, alpha = 65.704(5), beta = 89.155(6), gamma = 75.270(6) degrees, V = 1525(1)A3, Z = 2. Spectroscopic investigation reveals that the complex is highly soluble and stable in water at physiological pH values; as a consequence the complex may represent a potential candidate for the development of new studies on aqueous tantalum(v) chemistry for radiopharmaceutical applications. 相似文献
32.
Ulderico Mazzi Edoardo Roncari Giuliano Bandoli Dore A. Clemente 《Transition Metal Chemistry》1982,7(3):163-166
Summary The [PPh4][TcCl4(sal)] and [PPh4][ReOCl3(sal)] (sal=o-OC6H4CHO) complexes were synthesized from [PPh4]2[MCl6] (M=Tc or Re) and salicylaldehyde. The complexes were characterized by elemental analysis, magnetic susceptibility and conductivity measurements and i.r. spectrometry. The structure of [PPh4][TcCl4(sal)] was determined by x-ray methods and consists of well-separated units of octahedral [TcCl4(sal)]– anions and tetrahedral [PPh4]+ cations. The equatorial plane of the octahedron is formed by two Cl atoms and the chelated(2) sal group, with the resulting TcCl2(sal) unit approximately planar. Selected values in the anion are as follows: Tc-Cl(mean) 2.34(1), Tc-O(1) 2.04(2) and Tc-O(2) 1.98(2), O(1)---O(2)(byte) 2.83 Å; O(1)-Tc-O(2) 89.3(0.7)o. 相似文献
33.
Ulderico Mazzi Fiorenzo Refosco Giuliano Bandoli Marino Nicolini 《Transition Metal Chemistry》1985,10(4):121-127
Summary The reactions of the tridentate Schiff base ligandN-(2-hydroxyphenyl) salicylideneimine (HOPhsalH) with oxotetrachlororhenate (IV) have been investigated. The complexes (Bu4N)[ReOCl3(HOPhsal)], (Bu4N)[ReOCl2(OPhsal)],cis- [ReOCl(MeOH)(OPhsal)],trans-[ReOCl(MeOH)(OPhsal)] (1), trans-[ReOCl(OH2)(OPhsal)] · Et2O (2), trans-[ReOCl(OH2)(OPhsal)] · Me2CO,cis-[ReOCl(PPh3)(OPhsal)],cis-[ReOCl(PMe2Ph)(OPhsal)](3) have been synthesized and characterized. The crystal structures of(1), (2) and(3) have been solved from three-dimensional x-ray data by Patterson and Fourier methods and refined by least-squares methods to R 0.10 for(1), 0.042 for(2) and 0.059 for(3). In all the three complexes, the ligands surrounding the rhenium atom are at the apices of a distorted octahedron, with the equatorial ONO donor atoms of the tridentate Schiff base bent away from the Ooxo and toward the loosely bound MeOH in(1), H2O in(2) and Cl in(t3). The fourth equatorial substituent is Cl (1 and2) and PMe2Ph(3) and the rhenium atoms lie 0.30–0.37 Å above the best plane through the four equatorial atoms, in the direction of the Ooxo. All interatomic distances and angles are normal. 相似文献
34.
Summary
A plane, autonomous, noncritical differential system x=f(x) of classC
k is given. Under a suitable «discreteness» hypothesis on the behavior of orbits, the exeistence of a global first integral as regular as the field (provided k )is proved. 相似文献
35.
The application of the continuous state space model to unequally spaced sequence data is discussed and illustrated. The continuous model implies a discrete model for the observed data. Practical expressions for relevant discrete model quantities are given. These quantities are required for the digital processing of the data and in particular for the application of the Kalman and smoothing filter and related calculations. Applications illustrate the procedures. 相似文献
36.
Summary As a part of an investigation of the content of herbal drug preparations and herbal medicinal products, we have investigated
tinctures (prepared with 40:60 and 60:40 (%,v/v) ethanolwater) of calendular flower, milk-thistle fruit, and passion flower, which are, respectively, widely used for their
anti-inflammatory properties, to treat hepatic injuries, and to treat tension and difficulty falling asleep. The aim of this
work was to evaluate the flavonoid content, because flavonoids are the active constituents or markers of these herbal drugs,
and to establish the best solvent for the extraction of the constituents. The findings reported herein both confirm the presence
of several flavonoids previously identified in these herbal drugs and report the presence of others not previously described
and identified here for the first time. In general the flavonol content was highest in 60% tinctures. A rapid, reversed-phase
(RP) HPLC assay was developed and validated and enabled good separation of all classes of flavonoids including flavones, flavonols,
flavanonols, and flavanolignans. Aglycones and mono, di, and triglycosides (bothO-andC-derivatives) of the flavonoids are also easily and satisfactorily separated. This method is thus proposed for the analysis
of other herbal drugs or herbal drug preparations in which flavonoids are the active constituents or markers. 相似文献
37.