摘要:

Abstract2‐Tetrahydropyranyloxymethylated difuran and furanthiophene compounds have been obtained in high yields from the coupling of furan boronic acid/furfuryl boronic acid by focused microwave irradiatio

ISSN:0009-4536    

DOI:10.1002/jccs.200500119

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractWeakly bound dimer complexes FH—CO and FH—OC were investigated using variousab initioand density function theory (DFT) methods. This study compares the strengths of the H—C H‐bond in FH—CO and the H—O H‐bond in FH—OC. The energy difference between dimers, the H‐bond energy, the inter‐monomer distance, the inter‐monomer vibration frequencies, the red shift of the HF stretching frequency, and the elongation of HF bond, all demonstrate that the H—C H‐bond is stronger than the related H—O H‐bond, according to all methods. The calculated Gibbs energies of the formation of the two dimers show that the weakly bound complexes are unstable at room temperature (T = 298 K) and ordinary pressure (P = 1 atm). However, decreasing T or increasing P monotonically decreases ΔG and increases the related equilibrium constan

ISSN:0009-4536    

DOI:10.1002/jccs.200500120

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractThe interaction of zinc(II), lead(II), and cadmium(II) with Glutathione (S‐L‐glutamyl‐Lcysteinylglycine) as primary ligand and zwitterionic buffers (N‐[2‐Hydroxyethyl]piperazine‐N′‐[2‐ethanesulfonic acid]) (HEPES) and (N‐Hydroxyethyl]piperazine‐N′‐[2‐hydroxy‐propanesulfonic acid]) (HEPPSO) as secondary ligands were studied by potentiometric‐pH titration in 1:1:1 ratio at 25.0 °C and I = 0.1 mol.dm−3(KNO3). The formation constants of different normal and protonated binary and ternary complex species were calculated.Formation constants for the monohydroxy, and dihydroxy complexes for the binary systems M(II) + HEPES and M(II) + HEPPSO have been evaluated. The distribution curves for the various complex species as

ISSN:0009-4536    

DOI:10.1002/jccs.200500121

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractThe study is aimed to prevent the formation of the aluminium carbide compound Al4C3that negatively affects Al‐Si‐C based materials. The reaction products of elementary aluminium, silicon and graphite as well as aluminium with either β‐SiC or α‐SiC without and with graphite at temperatures 1200°‐2500 °C under different atmospheres and reaction times were characterized using powder X‐ray diffraction and scanning electron microscopy (SEM) with an energy dispersive X‐ray (EDX) analysis. The results of the powder diffraction study show that under the conditions (1450 °C; 8 h; vacuum) the formation of Al4C3could be prevented. The reaction products at those conditions consist of the ternary compound Al4SiC4besides SiC and residual carbon. The ternary aluminium silicon carbide Al4SiC4crystallizes in a hexagonal crystal system with unit cell dimensionsa= 327.64(4) pm,b= 2171.2(6) pm and space groupP63mc(no. 186). The crystal structure of Al4SiC4is isostructural with Al5C3N and consists of laye

ISSN:0009-4536    

DOI:10.1002/jccs.200500122

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractThe synthesis, structure, and magnetic properties of four 2,2′‐dipyridylamine ligand (abbreviated as Hdpa) containing copper(II) complexes. There is one binuclear compound, which is [Cu2(μ1,1‐NCO)2(NCO)2(Hdpa)2] (1), and three mononuclear compounds, which are [Cu{N(CN)2}2(Hdpa)2] (2), [Cu(CH3CO2)(Hdpa)2·N(CN)2] (3), and [Cu(NCS)(Acac)] (4).Compounds1and4crystallize in the monoclinic system, space groupP2(1)/candZ= 4, witha= 8.2465(6) Å,b= 9.3059(7) Å,c= 16.0817(12) Å, β = 91.090(1)°, andV= 1233.90(16) Å3for1anda= 7.6766(6) Å,b= 21.888(3) Å,c= 10.4678(12) Å, β = 90.301(2)°, andV=1758.8(4) Å3for4. Compounds2and3crystallize in the triclinic system, space groupP‐1andZ= 1, witha= 8.1140(3) Å,b= 8.2470(3) Å,c= 9.3120(4) Å, β = 102.2370(10)°, andV= 592.63(4) Å3for2anda= 7.4780(2) Å,b= 12.5700(3) Å,c= 13.0450(3) Å, β = 96.351(2)°, andV= 1211.17(5) Å3for3.Complex (1), the magnetic data was fitted by the Bleaney‐Bowers equation (1). A very good fit was derived withJ= 23.96, Θ = −1.5 (g = 1.97). Complex (1) shows the ferromagnetism. Complexes (2), (3) and (4) of have the it is the typical paramagnetic behavior of unpaired electrons. Under a low temperature around 25 K, complexes (2) and (3) show weak ferromagnetic behavior

ISSN:0009-4536    

DOI:10.1002/jccs.200500123

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractThe complexation between trimethoxyphenylflurone (TMPF) and Fe is highly sensitive at pH 11.80 in the presences of cetylpyridinium chloride (CPC) and thioglycolic acid (TGA), where TGA reduced TMPF into a reduced ligand (RTMPF) and Fe(III) into Fe(II). The complexations of RTMPF with CPC and Fe have been characterized by the break point approach and the spectral correction technique. The binuclear complex, Fe2(RTMPF)10(CPC)20was formed via coordination bond and ion‐pair attraction. The Fe‐TMPF‐CPC complexation is selective in the presence of ethylenediamine tetraacetic acid (EDTA) and Al(III) so it was applied to the spectrophotometric determination of total Fe(II+III) by the light‐absorption ratio variation approach (LARVA). Results indicated that ΔArof the Fe‐RTMPF solution is linear at 568 and 641.5 nm at the range between 0 and 100 ng/mL Fe. The limit of detection (3σ) of Fe is only 2 ng/mL. This method was applied to analysis of several samples such as natural waters, cigarette ash, and urine with satisfact

ISSN:0009-4536    

DOI:10.1002/jccs.200500124

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractThe analysis of17O NMR transverse relaxation rates and EPR transverse electronic relaxation rates for aqueous solutions of the four DTPA‐like (DTPA = diethylenetriamine‐N,N,N′,N″,N″‐pentaacetic acid) complexes, [Gd(DTPA‐PY)(H2O)]−(DTPA‐PY =N′‐(2‐pyridylmethyl)), [Gd(DTPA‐HP)(H2O)2]−(DTPA‐HP =N′‐(2‐hydroxypropyl)), [Gd(DTPA‐H1P)(H2O)2]−(DTPA‐H1P =N′‐(2‐hydroxy‐1‐phenylethyl)) and [Gd(DTPA‐H2P)(H2O)2] (DTPA‐H2P =N′‐(2‐hydroxy‐2‐phenylethyl)), at various temperatures allows us to understand the water exchange dynamics of these four complexes. The water‐exchange lifetime (τM) parameters for [Gd(DTPA‐PY)(H2O)]−, [Gd(DTPA‐HP)(H2O)2]−, [Gd(DTPA‐H1P)(H2O)2]−and [Gd(DTPA‐H2P)(H2O)2] are of 585, 98, 163, and 69 ns, respectively. Compared with [Gd(DTPA)(H2O)]2−(τM = 303 ns), the τM value of [Gd(DTPA‐PY)(H2O)]−is slightly higher, but the other three complexes values are significantly lower than those of [Gd(DTPA)(H2O)]2−. This difference is explained by the fact that the gadolinium(III) complexes of DTPA‐HP, DTPA‐H1P, and DTPA‐H2P have two inner‐sphere waters. The2H longitudinal relaxation rates of the labeled diamagnetic lanthanum complex allow the calculation of its rotational correlation time (τR). The τR values calculated for DTPA‐PY, DTPA‐HP, DTPA‐H1P, and DTPA‐H2P are of 127, 110, 142 and 147 ps, respectively. These four values are higher than the value of [La(DTPA

ISSN:0009-4536    

DOI:10.1002/jccs.200500125

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractAn alumina surface was modified by adsorption of an anionic surfactant, sodium dodecyl sulfate (SDS). Typical S‐shaped isotherm of surfactant on alumina was observed. The adsorption of Disperse Red‐11, Disperse Blue‐26 and Disperse Red‐156 on alumina and surfactant treated alumina has been investigated. The enhancement in adsorption of these disperse dyes on surfactant treated alumina is observed, which may be attributed to their solubilization in surfactant aggregates formed at the solid/liquid interface. The effect of pH on adsorption has been studied. The adsorption is greatly influenced by pH of the medium. The applicability of the Langmuir model and the Dual‐Mode sorption model (DSM) were tested for equilib

ISSN:0009-4536    

DOI:10.1002/jccs.200500126

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractThe emission spectra of quinidine and quinidine sulfate doped in sol‐gels (tetraethoxysiliane system) have been measured during the sol‐gel transformation. Shifts in the emission spectra from 370 nm to 435 nm were observed in both molecules as the system changed from sol stage to dried glass over a period of two weeks. These shifts are attributed to the conformational changes of the doped molecules. In addition, the process of the signal changes was observed by an emerging new band at ˜435 nm with a concomitant decline of the original band at 370 nm during the sol‐gel transformation. These results indicate that the conformational changes induced by the sol‐gel transformation are accomplished in one step instead of several intermediat

ISSN:0009-4536    

DOI:10.1002/jccs.200500127

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractThe purpose of this research was to develop an optimized pretreatment procedure for toxic metals (Pb, Cd, Zn and Cu) content in fly ash from a municipal waste incinerator. In addition, modified sequential extraction procedures were used to characterize the chemical composition of the fly ash samples. The sequential extraction resolved the fly ash elements into the following chemical forms: soluble, exchangeable, carbonate, oxide, organic, and silicate compounds. Certified reference city waste incineration ash (BCR.176) was used as target ash samples. A H2O2+HNO3+HF mixed acid digestion solution with a low temperature evaporation procedure was selected as optimal for the fly ash digestion. The digested solution was analyzed by inductively coupled plasma mass spectrometry (ICP‐MS), which effectively determined the concentrations of the toxic metal elements in BCR.176. Except for Cd, the recovery of Pb, Zn, and Cu under H2O2+HNO3+HF digestion and their sequential extraction procedures were higher than 95%. The relative standard deviations (RSD) for recoveries of the four elements were within 10%. Furthermore, the sequential extraction procedure's results provided information on the potential mobility of the studied elements. Most of the Cd was bound to water‐soluble and carbonate material in the fly ash samples. Most of the Pb, Zn, and Cu was released to carbonates and bound to organic matter in the fly ash samp

ISSN:0009-4536    

DOI:10.1002/jccs.200500128

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY