摘要:

AbstractThe determination of lanthanides by Inductively Coupled Plasma Mass Spectrometry (ICP‐MS) is complicated by several spectral overlaps from M+, MO+or MOH+ions formed in the ICP. Especially, it is essential to avoid the spectral interferences from lighter lanthanide and Ba polyatomic ions on middle or heavier lanthanides. To tackle this problem, we have developed a mathematical correction method, which reduces all the spectral overlaps from oxide species of Pr, Nd, Ce and Sm over Gd, Tb, Dy and Ho, and Gd, Tb over Yb and Lu. It can also successfully correct the oxide and hydroxide interference of Ba over Eu. The effectiveness of the proposed the mathematical correction scheme is demonstrated for the USGS Standard Rock samples AGV‐1 and G‐2. The results show that the experimental data obtained by applying the mathematical correction scheme for lanthanides is in good agreement with the reported values, using pneumatic and ultrasonic nebulisation methods, for their ICP‐MS a

ISSN:0009-4536    

DOI:10.1002/jccs.200500087

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractThe potential energy surfaces for the cycloaddition reactions of angle strained cycloalkynes to ethylene have been studied usingab initiomethods. All the stationary points were determined with the MP2/6–311G (d,p) method with some calculations performed at the CCSD(T)/6–311G++G(d,p)//MP2/6–311G (d,p) level. Three kinds of cycloalkyne species, including monocyclic alkynes, bridged bicyclic alkynes, and heterocyclic alkynes, have been chosen in this work as model reactants. Two different reaction pathways have been proposed: (A) 1,2‐carbon shift and (B) 1,2‐hydrogen shift. That is, reactants → [2+1]‐TS‐1 → spiro‐carbene intermediate → (A) TS‐A → Pro‐A or (B) TS‐B → Pro‐B. As a result, it is found that ground‐state cycloalkyne appears to react more like a monocarbene than like an alkyne or a vicinal dicarbene as conventionally proposed. Our theoretical investigations also suggest that a cycloalkyne with a small C‐C≡C bond angle should be a good candidate for cycloaddition to an olefin. Moreover, in the cycloaddition reaction of a small (≤ six‐membered ring six‐membered) ring cycloalkyne, both 1,2‐carbon and 1,2‐hydrogen migrations will compete with each other. On the other hand, reactions involving larger (≥ seven‐membered) ring cycloalkynes should proceed with a 1,2‐carbon shift, leading to the major [2+2]cycloadduct. Furthermore, a configuration mixing model has been used to rationalize the computational results and to develop an explanation for the barrier heights. The re

ISSN:0009-4536    

DOI:10.1002/jccs.200500088

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractThe ability of the equatorial C‐H bonds to form C‐H—O hydrogen bonds was studied by measuring the high‐pressure Raman spectra. We have investigated the effect of pressure versus C‐H—O interactions in 1,3‐dioxane/D2O mixtures. Dilution of 1,3‐dioxane leads to a shift of the C‐H signals to higher frequencies under ambient pressure. Based on the pressure‐dependence of the Raman spectra, we have found that the equatorial C‐H groups of 1,3‐dioxane displays a remarkably different ability to serve as the weak hydrogen bond donors in comparison to the axial C‐H of 1,3‐dioxane. The new Raman spectral features observed under high pressure may arise from the combined effect of hydrogen‐bond network changes, hydrogen bond‐like C‐H—O interactions formation, cluster size changes, etc. This finding may be important to diaste

ISSN:0009-4536    

DOI:10.1002/jccs.200500089

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractWe fitted published frequency and wave number data for pure rotational and vibration‐rotational spectra, respectively, of23Na35Cl and23Na37Cl to derive parameters related to potential energy and to the rotationalgfactor. For comparison with these experimental data we undertook quantum‐chemical computation of adiabatic corrections, rotational and vibrationalgfactors, electric dipolar moment and its derivative as a function of internuclear distance in a range nearReas a test of an algebraic approach to spectral analysis; experimental, 0.0287 ± 0.0014, and calculated, 0.02149, values ofgratReare in moderate agreement. The combined results are discussed from a point of view of computational spectrom

ISSN:0009-4536    

DOI:10.1002/jccs.200500090

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractA review of matrix‐isolation experiments performed in this laboratory for the past thirteen years (1992–2004) is given; the work emphasizes the preparation and spectral characterization of novel species of atmospheric interest, and the significance of detection of some species is discussed. A previous review (J. Chin. Chem. Soc.1992,39, 503) covers work from 1981 to 1991. Various methods for production of novel species, including reaction in the gaseous phase, laser photolysis of a single precursorin situ, reaction of a molecule with an atom or radical in a matrix cage and reaction of a molecule with an electronically excited molecule, are discussed. The effect of secondary photolysis on products is illustrated with formation of various conformers of HOONO from photolysis of HNO3. The advantage of investigating electronic transitions that are difficult to observe in the gaseous phase and the mode and site selectivity of photodissociation for species in a matrix cage are also discussed. New developments involving use ofp‐H2as a matrix host, including the introduction of a pulse‐deposition method for use at ˜5 K and the exploration of internal rotation of larger molecules in solidp‐H2, are also

ISSN:0009-4536    

DOI:10.1002/jccs.200500091

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractBased on electrokinetic equations, we calculate the dynamic response of the thin double layer of a charged surface. The double layer response acts as effective boundary conditions for the ion concentrations, flow field, and potential outside the double layer. The results can be used to further calculate the electrophoresis or the dielectric spectrum of the deformable charged suspensions.

ISSN:0009-4536    

DOI:10.1002/jccs.200500092

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractChemiluminescence (CL) from the cobalt(II)‐catalyzed oxidation of luminol with hydrogen peroxide was dramatically enhanced by the presence of carbonate. The CL signal increases by several orders of magnitude over a wide range of concentrations of Co(II), luminol, or hydrogen peroxide. A limit of detection of 10−12M for Co(II) and luminol and 10−8M for hydrogen peroxide can be achieved. The CL emission spectrum exhibits a maximum at 425 nm, indicating that the excited 3‐aminophthalate is the emitting species. ESR spin‐trapping experiments revealed a large increase in the production of hydroxyl and carbonate radicals by the presence of carbonate, which is responsible for the enormous CL enhancement. Uric acid, ascorbic acid, acetaminophen, andp‐hydroxyphenyl acetic acid are capable of scavenging the radicals, thereby inhibiting the CL emission. The inhibition of CL intensity can be used to determine these substances at the sub‐mic

ISSN:0009-4536    

DOI:10.1002/jccs.200500093

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractThe electronic and geometrical properties of distyrylbenzene (DSB) are investigated by using chemistry theoretical calculation methods. Specifically, the excited state properties are studied by performingab initiocorrelation interaction singlet (CIS) and time‐dependent density functional theory; the ground state and Raman activities are computed by density functional theory with the B3LYP method. Eight conformers of distyrylbenzene are found and they are derived from three isomers which arecis, cis‐, cis, trans‐, andtrans, trans‐, respectively. The relative energy shows that each isomer of three types is separated with a large energy barrier, but a small energy difference of each conformer is found if they are in the same type. The transition state also shows the barrier between conformers is lower than isomers. The computed excited transition energies using ZINDO/S based on the optimized geometries at a DFT/B3LYP level with 6–31+G show an excellent agreement with experimental absorptio

ISSN:0009-4536    

DOI:10.1002/jccs.200500094

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractFourier Transform spectroscopy with 10−8second time resolution for recording IR emission spectra has been developed as an efficient means for detecting previously unknown vibrational modes of transient radicals. 193 nm photodissociation of a precursor molecule is used to generate vibrationally excited radicals, from which IR emission is recorded with time and spectral resolution. Assignment of the spectra is performed using information obtained through multiple precursors, isotopic substitution, time dependence of emission intensity, theoretical calculations, and 2‐dimensional cross‐spectra correlation analysis. The radicals vinyl, cyanovinyl, and OCCN have been studied with many vibrational modes ident

ISSN:0009-4536    

DOI:10.1002/jccs.200500095

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY

摘要:

AbstractCoordination of a bulky pyridinyl‐phosphine (P˜N) ligand toward CuBr was investigated. However, thisP˜Ndonor behaves as a monodentateviathe coordination of phosphine to form a bromide bridged dimeric [(P˜N)Cu(μ‐Br)2Cu(P˜N)], which was characterized by spectral and crystal structural analysis. It appeared that the “PCu(μ‐Br)2CuP” unit is planar with a short distance between Cu…Cu' [2.7585(9) Å]. The catalytic activity on Sonogashira coupling of phenylacetylene with aryl h

ISSN:0009-4536    

DOI:10.1002/jccs.200500096

出版商:WILEY‐VCH Verlag    

年代:2005

数据来源: WILEY