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881.
H. Liu T. F. Yeh H. S. Lee T. A. Skotheim Y. Okamoto 《Journal of polymer science. Part A, Polymer chemistry》1992,30(5):879-885
2,6-Di-t-butylphenol and oligo(ethylene oxide) bound covalently to polyisocyanate were synthesized and characterized. The ionic conductivities of their Li, Na, and K phenolates were studied at various temperatures. The conductivities were in the range of 10?7?10?5 S/cm at 30°C. The conductivity of Na and K salts was approximately 102 greater than that of the Li salts. The t-butyl groups serve to dissociate K and Na ions from the phenoxide. The cations, therefore, are more mobile as a result increasing the conductivity. The temperature dependence of ionic conductivity suggests that the migration of ions is controlled by segmental motion of the polymer, shown by linear curves obtained in Vogel–Tammann–Fulchere plots. The polyisocyanate backbone is a rather stiff structure, however, a flexible oligo(ethylene oxide) side chain forms complexes with metal ion. Since the ion transport is associated with the local movement of polymer segments, the rigidity of the polymer backbone does not have much influence on the ion mobility. 相似文献
882.
A simple and sensitive HPLC method for quantitative determination of guanidine in high salt and protein matrices was developed. The HPLC system consisted of an Agilent 1100 pump with an online degasser, a UV detector, an autosampler, and Dionex CS 14 cation-exchange guard (4 mm x 50 mm) and analytical (4 mm x 250 mm) columns. The mobile phase was 3.75 mM methanesulfonic acid (MSA) with a flow rate of 1 mL/min. The other analysis parameters were: 50 microL injection volume, 195 nm UV detection, and 21 min runtime. The limit of quantitation (LOQ) for guanidine HCl was determined to be 0.25 mg/L and the standard curve ranged from 0.25 mg/L to 10 mg/L. Sample preparation was required for the samples containing high protein concentrations. Proteins were removed by centrifuging a sample in a 30 K NanoSep centrifugal filter at 15,300 x g for 20 min. The method could determine guanidine accurately in sample matrices containing up to 200 mM sodium ion or up to 50 mM potassium ion. The method can be used for clearance testing of guanidine in biopharmaceutical products. 相似文献
883.
Inmaculada Beloso Paulo Prez‐Lourido Jesús Castro Jos A. García‐Vzquez Jaime Romero 《无机化学与普通化学杂志》2005,631(11):2101-2106
Heteroleptic nickel(II) complexes [NiL2L′] of a series of monoanionic and potentially bidentate N‐2‐pyridyl‐sulfonamide ligands [HL] and 2,2′‐bipyridine or 1,10‐Phenanthroline (L′) have been prepared by electrochemical oxidation of a nickel anode in an acetonitrile solution of the ligands. The complexes have been characterized by microanalysis, IR and electronic spectroscopy, magnetic measurements and LSI mass spectrometry. The crystal structure of [Ni(Ms6mepy)2(bipy)] has been determined by x‐ray diffraction and shows the metal in an octahedral NiN6 environment. Octahedral structures are also proposed for the other complexes with the N‐2‐pyridyl‐sulfonamide ligands acting as N,N′ or N, O bidentate systems, depending on the position of the methyl substituent on the pyridine ring. 相似文献
884.
Two new coordination polymers of PbII complexes with bridging 4,4′‐[(1E)‐ethane‐1,2‐diyl]bis[pyridine] (ebp), thiocyanato, and acetato ligands, [Pb(μ‐SCN)2(μ‐ebp)1.5]n ( 1 ) and {[Pb(μ‐OAc)(μ‐ebp)](ClO4)}n ( 2 ), were synthesized and characterized by elemental analysis, FT‐IR, 1H‐ and 13C‐NMR, thermal analysis, and single‐crystal X‐ray diffraction. In 1 , the Pb2+ ions are doubly bridged by both the ebp and the SCN− ligands into a two‐dimensional polymeric network. The seven‐coordinate geometry around the Pb2+ ion in 1 is a distorted monocapped trigonal prism, in which the Pb2+ ions have a less‐common holodirected geometry. In 2 , the Pb2+ ions are bridged by AcO− ligands forming linear chains, which are also further bridged by the neutral ebp ligands into a two‐dimensional polymeric framework. The Pb2+ ions have a five‐coordinate geometry with two N‐atoms from two ebp ligands and three O‐atoms of AcO−. Although ClO acts as a counter‐ion, it also makes weak interactions with the Pb2+ center. The arrangement of the ligands in 2 exhibits hemidirected geometry, and the coordination gap around the Pb2+ ion is possibly occupied by a configurationally active lone pair of electrons. 相似文献
885.
886.
Six new ent‐abietane diterpenoids, rubescensins I–M ( 1 – 5 ) and P ( 6 ), along with two related acetonide derivatives ( 7 and 8 ), were isolated from Isodon rubescens. Their structures were elucidated by detailed spectroscopic analysis. Compound 5 is the first N‐containing diterpenoid from the genus Isodon, exhibiting notable cytotoxicity against human tumor K562 cells. 相似文献
887.
K. No Hyun J. Lee Ki M. Park Shim S. Lee Kwan H. Noh Sung K. Kim Ji Y. Lee Jong S. Kim 《Journal of heterocyclic chemistry》2004,41(2):211-219
A series of novel 1,3‐altemate calix[4]arene azacrowns having mono and bis crown ethers on the lower rim of the calix[4]arene framework were synthesized. Solid‐state structures confirmed the three dimensional conformation of compounds 1–3. 相似文献
888.
Mohamed S. A. El‐Gaby Ahmed M. Sh El‐Sharief Ahmed A. Atalla Abu‐Bakr A. A. M. El‐Adasy 《中国化学会会志》2004,51(2):327-333
The novel cyanothioformamides 2a‐d were prepared by treatment of isothiocyanatosulfonamides 1a‐d with potassium cyanide at room temperature. Cyclocondensation of compounds 2b,c with phenyl isocyanate as electrophile furnished the corresponding imidazolidines 3a,b . The reactivity of compound 3a towards some nitrogen nucleophiles was investigated. Thus, the thiosemicarbazone 4 and imidazo[4,5‐b]quinoxaline 6 were synthesized by condensation of compound 3a with thiosemicarbazide and o‐phenylenediamine, respectively. Treatment of 3a with hydrochloric acid afforded compound 7 . Our investigation was extended to include the reactivity of cyanothioformamide 2 towards o‐aminophenol, anthranilic acid, and o‐phenylenediamine and yielded the corresponding heterocycles 9 , 11 and 13 derivatives, respectively. Structures of the synthesized compounds were established by their elemental analysis and spectral data. 相似文献
889.
The flow of condensible vapors through microporous Vycor glass was investigated experimentally as well as theoretically. In porous materials, adsorbable gases frequently exhibit higher permeability than predicted from the flow of nonadsorbable gases. This enhanced flow has been attributed to the surface diffusion of adsorbed molecules along the surface of the porous media or to the viscous flow of capillary condensate at high relative pressures. In the present investigation, a new flow model of condensible vapors through microporous material was developed by considering the blocking effect of the adsorbed phase on the basis of a cylindrical capillary structure. Six different flow modes were considered depending on the pressure distribution and the film thickness of the adsorbed layer. Experimental measurements were also conducted on the transport of condensible vapors (Freon-113 and water) through microporous Vycor glass at steady state in the entire range of relative pressure. The maximum peak and scattering phenomena of permeabilities were observed. The estimated values of permeability from the developed model were compared with the experimental results. Also, it was attempted to explain the maximum peak and scattering phenomena of the experimentally observed permeabilities. 相似文献
890.
Feng‐You Hao Yong‐Fang Zhao Xiao‐Gong Jing Xin‐Ying Li Feng‐Li Liu 《International journal of quantum chemistry》2007,107(6):1502-1507
Ab initio quantum chemical calculations have been performed on X2Cl? and X2Cl (X = C, Si, Ge) clusters. The geometrical structures, vibrational frequencies, electronic properties and dissociation energies are investigated at the Hartree–Fock (HF), Møller–Plesset second‐ and fourth‐order (MP2, MP4), CCSD(T) level with the 6‐311+G(d) basis set. The X2Cl (X = C, Si, Ge) and X2Cl? (X = Si, Ge) take a bent shape obtained at the ground state, while C2Cl? has a linear structure. The impact on internal electron transfer between the X2Cl and the corresponding anional clusters is studied. The three different types of electron affinities (EAs) at the CCSD(T) are reported. The most reliable adiabatic electronic affinities, obtained at the CCSD(T)/cc‐pvqz level of theory, are predicted to be 3.30, 2.62, and 1.98 eV for C2Cl, Si2Cl, and Ge2Cl, respectively. The calculated EAs of C2Cl and Ge2Cl are in good agreement with theoretical results reported. The correlation effects and basis sets effects on the geometrical structures and dissociation energies are discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献