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51.
Otto M Schirmer A Claussnitzer U Pfeffer M 《Analytical and bioanalytical chemistry》2002,372(2):341-346
Optimisation of the separation of a synthetic drug mixture by HPLC is performed by changing both continuous variables, i.e. mobile phase composition and temperature, and categorical variables, here the stationary phase. The retention of solutes is described on the basis of a general linear model in which the different columns are modelled by indicator variables. From the solute-specific retention models the global separation optimum is evaluated on the basis of multidimensional window diagrams using relative retentions of all peak pairs as the figure-of-merit. 相似文献
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Two types of side group polysiloxanes which differ in their spacer between backbone and mesogenic part were synthesized via polymer analogous reaction. The impact of an oxygen atom localized in the γ position to the siloxane main chain on the ferroelectric properties was investigated. In addition, the link between the terminal chiral moiety and the mesogenic part in each series was varied. The phase transition behaviour, spontaneous polarization and the electro-optical response time for the two series of polymers are compared. The mesophase structures were determined by X-ray measurements on magnetically oriented samples at different temperatures. The additional oxygen atom in the spacer near to the main chain leads to broader range smectic C* phases and shorter electro-optical response times, which suggests that the ether linkage promotes a better decoupling between main chain and mesogenic side group. 相似文献
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Christmann U Dau H Haumann M Kiss E Liebisch P Rehder D Santoni G Schulzke C 《Dalton transactions (Cambridge, England : 2003)》2004,(16):2534-2540
The EXAFS region of vanadium K-edge XAS spectra of native vanadate-dependent bromoperoxidase (isoenzyme I) from Ascophyllum nodosum in the presence of the substrate bromide can be fitted to three shells (at 1.62, 1.73-1.78 and 1.99-2.07 A) in the first coordination sphere of vanadium plus two more distant shells at 4.1A, possibly corresponding to bromide, and 4.7 A due to light scatterers stemming from the protein pocket. Bromide does not directly bind to the vanadium centre. The XANES and the EXAFS features for the enzyme are essentially reproduced by model complexes of the general composition [VO(H(2)O)(n)(ONO)] (n= 1 or 2) where ONO is the dianion of a Schiff base from bromosalicylaldehydes (Brsal; with the Br substituent in the position 3, 4, 5 or 6) and amino acids. The 3-Brsal derivatives exhibit an outer sphere shell at 3.8 A, which is traced back to intermolecular contacts. The data obtained from EXAFS are compared to those obtained from single crystal X-ray diffraction of [VO(H(2)O)(2)(4-Brsal-gly)] and [VO(H(2)O)(2)(6-Brsal-gly)] (gly = glycinate). In the complex [VOBr(2)(ONO)']] ((ONO)' is the Schiff base from o-anisole and o-hydroxyaniline), the V-Br distance is 2.44 A. 相似文献
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Wolfgang Scherer Prof. Dr. Christoph Hauf Dipl.‐Phys. Manuel Presnitz Dipl.‐Phys. Ernst‐Wilhelm Scheidt Dr. Georg Eickerling Dr. Volker Eyert Dr. Rolf‐Dieter Hoffmann Dr. Ute C. Rodewald Dipl.‐Ing. Adrienne Hammerschmidt Dr. Christian Vogt Dr. Rainer Pöttgen Prof. Dr. 《Angewandte Chemie (International ed. in English)》2010,49(9):1578-1582
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Muhammad Nawaz Tahir Markus Messerschmidt Michael Klein Victor Martinez Patrick Theato Nadine Metz Sonngard Hartmann Ute Kolb Vadim Ksenofontov Franz Renz Wolfgang Tremel 《Polyhedron》2009,28(9-10):1728-1733
The precursor [FeIII(L)Cl (L = N,N′-bis(2′-hydroxy-3′-methyl-benzyliden)-1,7-diamino-4-azaheptane) is combined with [Mo(CN)8]4? yields a star shaped nona-nuclear cluster, [MoIV{(CN)FeIII(L)}8]Cl4. This Fe8Mo molecule is a high-spin system at room temperature. On cooling to 20 K some of the iron(III) centres in the molybdenum(IV)-star switch to the low-spin state as proven by Mössbauer spectroscopy. This molecule was deposited on TiO2 nanowires by electrostatic interactions between the cluster cations and the surface functionalized titanium oxide nanowire. The synthesis and surface binding of the multistable molecular switch was demonstrated using IR and UV–Vis spectroscopy (high-resolution) transmission electron microscopy ((HR)TEM) and Mössbauer spectroscopy. High- and low-temperature Mössbauer spectra indicate that the spin state transition of the free cluster molecules is preserved after surface binding. The above results emphasize the possibility of fabricating molecule-based low-dimensional structures by using traditional bottom-up approaches based on the electrostatic interaction between the cluster cations and polymer functionalized nanowires. These results can be generalized for the application to both charged and non-charged molecules. 相似文献
60.
Tomohiro Hirano Shuhei Masuda Shou Nasu Koichi Ute Tsuneyuki Sato 《Journal of polymer science. Part A, Polymer chemistry》2009,47(4):1192-1203
Radical polymerization of N,N‐dimethylacrylamide (DMAAm) was investigated in the presence of tartrates, such as diethyl L ‐tartrate, diisopropyl L ‐tartrate, and di‐n‐butyl L ‐tartrate, in toluene at low temperatures. Syndiotactic polymers were obtained in the presence of tartrates, whereas isotactic polymers were obtained in the absence of tartrates. The syndiotactic‐specificity increased with increasing amount of tartrates and with decreasing polymerization temperature. NMR analysis suggested that DMAAm and tartrates formed a 1:1 complex through double hydrogen bonding. A mechanism for the syndiotactic‐specific radical polymerization of DMAAm is proposed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1192–1203, 2009 相似文献