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151.
Spange S Kunzmann D Sens R Roth I Seifert A Thiel WR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(17):4161-4167
Azamethine dyes of the merocyanine type [4-(N,N-di-n-butylamino)-2-methylphenyl][2,4-di-keto-3-[N'-(n-hexyl)]-5-cyano-6-methyl-3-pyridinio]-1-azamethine (1) and [4-(N,N-diethylamino)-2-(N'-tert-butylcarboxy)-amidophenyl]-[2,4-diketo-3-[N"-(n-hexyl)]-5-cyano-6-methyl-3-pyridinio]-1-azamethine (2) have been used as surface-polarity indicators for gold-cluster-functionalized silica particles. Their UV/Vis absorption maxima range from about lambda=600 to 700 nm as a function of solvent polarity and are clearly separated from the surface plasmon UV/Vis absorption band of gold (lambda approximately 520-540 nm). Solvatochromism of both dyes has been investigated in 26 solvents of different polarity. The positive solvatochromic band shifts of 1 and 2 can be well expressed in terms of the empirical Kamlet-Taft solvent polarity parameters alpha and pi*. They are mainly sensitive to the dipolarity/polarizability (pi* term; 70-75 %) and HBD (hydrogen-bond donating) acidity (alpha term) of the solvent. Both dyes adsorb readily on functionalized silica samples from solutions in 1,2-dichloroethane or cyclohexane. The surface polarities of gold-cluster-functionalized silica particles, with and without co-adsorbed L-cysteine and poly(ethylenimine), have been investigated by using these solvatochromic dyes. The specific interaction of dye 2 with cysteine has been examined independently by quantum-chemical calculations by using the AM1 and PM3 methods. 相似文献
152.
Bernhardt E Willner H Jonas V Thiel W Aubke F 《Angewandte Chemie (International ed. in English)》2000,39(1):168-171
The first carbonyl compound of a transition metal in the oxidation state +6 was obtained by reductive carbonylation of OsO(4) in SbF(5). Through the use of extensive IR, NMR, and UV/Vis spectroscopic studies as well as density functional calculations it was determined that the trans-[OsO(2)(CO)(4)](2+) cation adopts the octahedral structure shown in the picture with trans oxygen atoms. 相似文献
153.
R. S. H. Liu Erik Krogh Xiao-Yuan Li Dennis Mead L. U. Colmenares J. R. Thiel Jeannette Ellis Darren Wong A. E. Asato 《Photochemistry and photobiology》1993,58(5):701-705
Prompted by the near infrared-absorbing properties of some of the azulenic bacteriorhodopsin (bR) analogs, we have analyzed their absorption characteristics along with 11 new related ring-fused analogs and the corresponding Schiff bases (SB) and protonated Schiff bases (PSB). The following three factors are believed to contribute to the total red shift of each of the pigment analogs (αRS): perturbation of the basic chromophore (SB shift, ΔSB), protonation of the SB (PSB shift, PSBS) and protein perturbation (the opsin shift, OS). For each factor, effects of structural modifications were examined. For the red-shifted pigments, percent OS has been suggested as an alternate way of measuring protein perturbation. Computer-simulated chromophores provided evidence against any explanation involving altered shapes of the binding pocket as a major cause for absorption differences. Implications of the current bR results on preparation of further red-shifted bR and possible application to visual pigment analogs are discussed. 相似文献
154.
Derat E Cohen S Shaik S Altun A Thiel W 《Journal of the American Chemical Society》2005,127(39):13611-13621
The active species, Compound I, of horseradish peroxidase (HRP) has been investigated by quantum mechanical/molecular mechanical (QM/MM) calculations using 10 different QM regions. In accord with experimental data, the lowest doublet and quartet states are found to be virtually degenerate, with two unpaired electrons on the FeO moiety and one localized on the porphyrin in an a(2u)-dominant orbital with a minor, but nonnegligible, a(1u) component. The proximal ligand appears to be imidazole rather than imidazolate. The hydrogen-bonding network around the FeO moiety (i.e., Arg38 and His42) has significant influence on the axial bonds and the spin density distribution in the FeO moiety. Including this network in the QM region was found to be essential for reproducing the experimental M?ssbauer parameters. The protein environment shapes most of the subtle features of Compound I of HRP. 相似文献
155.
Classification of wine samples by means of artificial neural networks and discrimination analytical methods 总被引:2,自引:0,他引:2
Li-Xian Sun Klaus Danzer Gabriela Thiel 《Fresenius' Journal of Analytical Chemistry》1997,359(2):143-149
The three-layer artificial neural network (ANN) model with back-propagation (BP) of error was used to classify wine samples
in six different regions based on the measurements of trace amounts of B, V, Mn, Zn, Fe, Al, Cu, Sr, Ba, Rb, Na, P, Ca, Mg,
K using an inductively coupled plasma optical emission spectrometer (ICP-OES). The ANN architecture and parameters were optimized.
The results obtained with ANN were compared with those obtained by cluster analysis, principal component analysis, the Bayes
discrimination method and the Fisher discrimination method. A satisfactory prediction result (100%) by an artificial neural
network using the jackknife leave-one-out procedure was obtained for the classification of wine samples containing six categories.
Received: 12 July 1996/Revised: 9 October 1996/Accepted: 12 October 1996 相似文献
156.
Goossen LJ Koley D Hermann H Thiel W 《Chemical communications (Cambridge, England)》2004,(19):2141-2143
Based on DFT calculations, a new mechanism for the oxidative addition of aryl halides to Pd-catalysts is presented. The key intermediate is an anionic Pd-species in which the aryl halide coordinates to the palladium via the halide atom. 相似文献
157.
Preparation and properties of N(HgCH3)3 are described and the mass spectrum. 1H-nmr spectrum and the vibrational spectrum (IR, RAMAN ) were recorded and assigned. In the solid state N(HgCH3)3 belongs to the point group C1, whereas in solution the molecule becomes more symmetric (C3v). On the contrary, the structure of the isoelectronic [O(HgCH3)3]+1 is trigonal planar (D3h). The vibrational spectrum of O(HgCH3)2 has been reinvestigated. 相似文献
158.
Pressure dependence of secondary ion emission from selected transition metals under nitrogen dioxide
For Ar+ bombarded polycrystalline surfaces of Ta, Co, Ni, Pd and Pt the emission of positive secondary ions was observed using nitrogen dioxide as reactant gas with varied partial pressure (0.001 mPa <p
{spno}2 < 10 mPa) and dynamic SIMS conditions (2 keV; 32 A/cm2). The results indicate that NO2 molecules appear to be completely destroyed in adsorption to Ta. Different behaviour was found for the other target metals. This can be explained by assuming surface species of partially molecular type. In some cases the results indicate two different modes of surface interaction with the reactant gas. 相似文献
159.
A galvanic cell was constructed to measure the e.m.f. for the solid-state reaction: 2NaCl+CdCl2 = Na2CdCl4 in the temperature range from 548 to 668 K. The electrodes were graphite disks in a chlorine atmosphere; Nasicon was used as Na+-conducting separator. The temperature variation of ΔG was linear in the limit of error. That could be proved by heat-capacity measurements and by determining the enthalpy of formation at T = 298.15 K. The thermodynamic functions were also determined for the compound Na0.77CdCl2.77 existing above 609 K and for the Suzuki-phase Na6CdCl8. The most important result for crystal chemistry is that entropy effects can be dominating for the formation of ternary halides. 相似文献
160.
Vibrationally-resolved photoelectron angular distributions for the first four valence-shell photoionizations of cyanogen have been measured with NeI, HeI and NeII line sources. Calculated photoionization cross sections and asymmetry parameters are reported for photon energies up to 50 eV. The experimental and theoretical results indicate the presence of several shape resonances. 相似文献