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991.
Chao Chen Yu-Lin Yang Kun-Lin Huang Zhen-Hua Sun Wei Wang Zhuo Yi Yun-Ling Liu Wen-Qin Pang 《Polyhedron》2004,23(18):3033-3042
With a hydrothermal technique, a layered titanium phosphate with the formula Ti2(H2PO4)(HPO4)(PO4)2 · 0.5C6N2H16 (denoted TP-J2) has been prepared by treating the Ti/H3PO4/H2O/1-methylpiperazine system directly. The as-synthesized products were characterized by powder X-ray diffraction, CP-MAS solid-state 31P NMR spectroscopy, thermogravimetric and differential thermal analyses (TG-DTA). The structure was solved by single-crystal X-ray diffraction analysis and it presents an extended γ-phase intercalated with organic amine. Crystal data: triclinic, , a = 8.106 (2) Å, b = 8.197 (2) Å, c = 11.658 (2) Å. = 78.32 (3)°, β = 80.85 (3)°, γ = 77.90 (3)°, Z = 2. Additionally, the intercalation behavior of TP-J2 with n-alkyl monoamine (n = 2, 3, 4, 6, 8, 10 and 12) was investigated. Owing to the strong brønsted base, N,N′-dimethylpiperazine, resides in the interlayer, it presented unusual features of TP-J2 in contrast with that of γ-Tip. 相似文献
992.
Biing-Jiun Uang I-Pin Fu Chyuan-Der Hwang Chun-Wei Chang Chun-Tzu Yang Der-Ren Hwang 《Tetrahedron》2004,60(46):10479-10486
A highly enantioselective addition of trimethylsilylcyanide to aldehydes catalyzed by chiral titanium complexes is described. The chiral titanium complexes were prepared in situ from Ti(OiPr)4 and β-hydroxyamide ligands, that could easily be synthesized from ketopinic acid and C2 symmetrical chiral diamines in a small number of steps. 相似文献
993.
Blend membranes (RCF1) were prepared from mixture solution of cellulose and silk fibroin (SF) in cuoxam by coagulating with acetone–acetic acid (4:1 by volume). The blend membranes were subjected to post-treatment with 10% NaOH aqueous solution, and their structure and properties were characterized by FT-IR, X-ray diffraction, DSC, SEM and DMTA. In previous work, cellulose/SF blend membranes (RCF2) prepared by coagulating with 10% NaOH aqueous solution formed a microporous structure, in which the SF as a pore former was almost completely removed from the membrane. However, when the blend membranes RCF1 were immersed in 10% NaOH aqueous solution for post-treatment, a strong hydrogen bonding between cellulose and SF inhibited the removal of SF. Although alkali is a good solvent for SF, the blend membranes RCF1 such obtained from cellulose and SF were alkali resistant. The crystallinity and the mean pore size of the blend membranes slightly decreased with increasing post-treatment time. This work provided a cellulose/silk blend membrane, which can be used under alkaline medium. 相似文献
994.
A new ligand, 2-carboxybenzaldehyde-(4’-hydroxy)benzoylhydrazone(H2L) and its ZnII and NiII complexes have been synthesized and characterized on the basis of elemental analyses, molar conductivities, 1H-NMR, IR spectra and thermal analyses. In addition, DNA-binding properties of these two metal complexes were investigated
using spectrometric titrations, ethidium bromide displacement experiments, and viscosity measurements. The results show that
the two complexes, especially the NiII complex, strongly bind with calf-thymus DNA, presumably via an intercalation mechanism. The intrinsic binding constants of the ZnII and NiII complexes with DNA are 2.46 × 105 and 7.94 × 105
M
−1, respectively. 相似文献
995.
ZnO biointerfaces with serum albumin have attracted noticeable attention due to the increasing interest in developing ZnO-based materials for biomedical applications. ZnO surface morphology and chemistry are expected to play a critical role on the structural, optical, and electronic properties of albumin-ZnO complexes. Yet there are still large gaps in the understanding of these biological interfaces. Herein we comprehensively elucidate the interactions at such interfaces by using atomic force microscopy and nanoshaving experiments to determine roughness, thickness, and adhesion properties of BSA layers adsorbed on the most typical polar and non-polar ZnO single-crystal facets. These experiments are corroborated by force field (FF) and density-functional tight-binding (DFTB) calculations on ZnO-BSA interfaces. We show that BSA adsorbs on all the studied ZnO surfaces while interactions of BSA with ZnO are found to be considerably affected by the atomic surface structure of ZnO. BSA layers on the surface have the highest roughness and thickness, hinting at a specific upright BSA arrangement. BSA layers on surface have the strongest binding, which is well correlated with DFTB simulations showing atomic rearrangement and bonding between specific amino acids (AAs) and ZnO. Besides the structural properties, the ZnO interaction with these AAs also controls the charge transfer and HOMO-LUMO energy positions in the BSA-ZnO complexes. This ZnO facet-specific protein binding and related structural and electronic effects can be useful for improving the design and functionality of ZnO-based materials and devices. 相似文献
996.
Dipole-moment derivatives, calculated by both the CNDO/2 method with different parameterizations and the INDO method, are compared to the experimental values determined from absolute infrared intensity measurements for the IR active modes of methane, ethane, ethylene and acetylene. A parameter refinement procedure is introduced in which the CNDO/2 molecular orbital parameters are adjusted through a damped least-squares treatment to give best agreement with the observed dipole-moment derivatives. It is found that the refinement does not substantially improve the agreement obtained with the original CNDO/2 parameterization. The INDO method gives somewhat poorer agreement than the CNDO/2 calculations. As an example of the applicability of the molecular orbital methods toward reproducing relative infrared intensities, the spectrum of cyclopropane in the gasphase is examined.
Zusammenfassung Die Ableitungen des Dipol-Moments, die nach der CNDO/2-Methode mit verschiedenen Parametrisierungen sowie der INDO-Methode berechnet wurden, werden mit den experimentellen Ergebnissen aus Messungen der absoluten Infrarot-Intensitäten für die IR-aktiven Schwingungen von Methan, Äthan, Äthylen und Azetylen verglichen. Die CNDO/2-Parameter werden mit einer Methode der kleinsten Quadrate den beobachteten Dipol-Moment-Ableitungen angepaßt. Die Ergebnisse sind jedoch nicht wesentlich von denen der ursprünglichen CNDO/2-Methode verschieden. Die INDO-Ergebnisse sind nicht so gut wie die CNDO/2-Ergebnisse. Als Beispiel der Anwendbarkeit der MO-Methoden zur Berechnung von relativen IR-Intensitäten wird das Spektrum des Cyclopropans in der Gasphase untersucht.
Résumé Les dérivées du moment dipolaire, calculées par la méthode CNDO/2 avec différentes paramétrisations et par la méthode INDO, sont comparées aux valeurs expérimentales déterminées à partir de mesures d'intensité absolue pour les modes actifs dans l'infra-rouge dans le méthane, l'éthane, l'éthylène et l'acétylène. Les paramètres sont ajustés de manière à donner le meilleur accord avec les dérivées du moment dipolaire. Cet ajustement n'améliore pas sensiblement l'accord obtenu avec la paramétrisation CNDO/2 originale. La méthode INDO donne des résultats moins bons que les calculs CNDO/2. Le spectre du cyclopropane en phase gazeuse est étudié comme exemple de l'applicabilité de la méthode des orbitales moléculaires au calcul des intensités relatives infra-rouge.相似文献
997.
Chin-Ping Yang Tzong-Ming Lee 《Journal of polymer science. Part A, Polymer chemistry》1989,27(7):2239-2251
4-Hydroxy-3,5-dibromobenzyl phosphonates (HDBBP) were synthesized by reacting phosphites with 4-hydroxy-3,5-dibromobenzyl bromide (HDBBB) which was prepared in advance by photobromination of 2,6-dibromo-p-cresol (DBPC) produced by bromination of p-cresol. In the reactions between HDBBB and phosphites, the rate of formation of dimethyl 4-hydroxy-3,5-dibromobenzyl phosphonate (HDBBPm) was greater than that of diphenyl 4-hydroxy-3,5-dibromobenzyl phosphonate (HDBBPP); however, quantitative yields for both products were obtainable. The addition of HDBBP as bromine and phosphorus containing flame-retardants to ABS copolymer showed better results than the addition of the same amount of brominated compound, or mixtures of both two compounds. It was also proved that compound containing both bromine and phosphorus exhibited more apparent synergistic effects on flame retardancy than the mixtures of brominated compound and phosphorous containing compound 相似文献
998.
In recent years, extensive efforts have been made to find nonformaldehyde durable press finishes to replace the traditional
formaldehyde-based reagents for producing wrinkle-free cotton fabrics. 1,2,3,4-butanetetracarboxylic acid (BTCA) has been
the most effective nonformaldehyde crosslinking agent. Our previous research has indicated that a polycarboxylic acid esterifies
cellulose in two steps: the formation of a 5-membered cyclic anhydride intermediate by the dehydration of two adjacent carboxyl
groups, and the reaction between cellulose and the anhydride intermediate to form an ester linkage. In this research, we used
Fourier transform infrared and Fourier transform Raman spectroscopy to study the formation of cyclic anhydride intermediates
by BTCA and other polycarboxylic acids without the presence of a catalyst. We found that BTCA and other polycarboxylic acids
in a crystalline state start to form 5-membered cyclic carboxylic anhydrides when the temperature reaches the vicinity of
their melting points with the exception of bifunctional acids, which form cyclic anhydrides at temperatures much higher than
their melting points. Intermolecular hydrogen bonding between carboxylic acid groups prevents the formation of the cyclic
anhydride intermediates at lower temperatures. We also found that polycarboxylic acids in an amorphous state form cyclic anhydrides
at much lower temperatures. 相似文献
999.
A capillary zone electrophoretic method has been developed for the quantitative analysis of five phenolic glucosides, 6′-O-vanilloylarbutin (VA), 7-O-feruloylorientin (FE), lutonarin (LN), isoorient (IO) and luteolin (LL), in Gentiana piasezkii with UV detection at 270 nm. 7-O-β-D-glucosyl-coumarin was selected as the internal standard. The applied voltage was 15 kV and the capillary temperature was kept constant at 25 °C. The effect of pH, the concentration of methanol and boric acid on migration were studied systematically. Optimum separation was achieved with 200 mM boric acid buffer at pH 9.50 containing 10% (v/v) methanol. Regression equations revealed good linear relationship between the peak area ratio of each compound and internal standard and its concentration. The correlation coefficients were 0.9975, 0.9997, 0.9998, 0.9998 and 0.9988 for VA, FE, LN, IO and LL, respectively. The relative standard deviations of migration time and the peak area ratio of each analyte and internal standard were <1.78% and 4.93%, respectively. The contents of the five compounds in Gentiana piasezkii were successfully determined with satisfactory repeatability and recovery. 相似文献
1000.
Wang BB Zhang X Jia XR Li ZC Ji Y Yang L Wei Y 《Journal of the American Chemical Society》2004,126(46):15180-15194
PAMAM dendrimers of the zeroth to fifth generation (G0-5) have been peripherally modified with phenyl, naphthyl, pyrenyl, and dansyl chromophores. Their fluorescence behaviors are strongly affected by the dendritic architectures at different generations. These dendrimers modified with hydrophobic chromphores can self-organize into vesicular aggregates at the low generations G0-3 in water. The size and aggregation number of these vesicles decrease with increasing generation from G0 to G3. Critical aggregation concentration determined by fluorescence spectroscopy reveals that these aggregates can be favorably formed in the order of G3 > G2 > G1. In contrast to the vesicles made from traditional amphiphilic compounds, these dendrimer-based vesicles are very adhesive due to the H-bonding interaction and entanglement of dendritic branches located in the outer layer. A large number of multivesicle assemblies, i.e., "twins" and "quins" consisting of two and five vesicles, were clearly identifiable with transmission electron (TEM) and atomic force microscopy. For the dendrimers with peripheral pyrenyl chromophores, triangle-like vesicles were observed in water. The hydrophobic interphase thickness of the vesicular bilayer is ca. 2.0-3.2 nm determined by fluorescence resonance energy transfer methods, which agrees well with the thickness directly observed with TEM. 相似文献