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排序方式: 共有323条查询结果,搜索用时 312 毫秒
101.
102.
A new highly Tl(I)-selective PVC membrane electrode based on tetrathia macrocycle 6,7: 14,15-dibenzo-5,8,13,16-tetraoxo-1,4,9,12-tetrathiacyclohexadecane [Bz2O4(16)aneS4] (I) as membrane carrier, o-nitrophenyloctyl ether (o-NPOE) as solvent mediator and potassium tetrakis(p-chlorophenyl)borate (KTpClPB) as lipophilic additive has been developed. The best performance was given by the membrane of macrocycle (I) with composition 3:120:1.5:50 (I:o-NPOE:KTpClPB:PVC). This electrode exhibits a Nernstian response to Tl(I) ions in the concentration range 1.0 × 10−1-2.23 × 10−6 M with a slope of 58.2 mV/decade of concentration and a detection limit of 1.58 × 10−6 M. The response time of the sensor is 12 s and can be used over a period of 4 months with good reproducibility. The proposed electrode revealed good selectivity over a wide variety of other cations including alkali, alkaline earth, heavy and transition metals. The electrode works well over a pH range of 3.2-11.5 and in partially non-aqueous medium with up to 30% organic content. The sensor was also used as an indicator electrode in potentiometric titration of Tl(I) ions with KI solution. 相似文献
103.
Paul B. Savage William D. Thomas N. Kent Dalley 《Journal of inclusion phenomena and macrocyclic chemistry》1997,29(3-4):335-346
Preparation of two new glycophanes is reported. These compounds arecomprised of two glucose molecules linked by hydrocarbon units at the 1,1 and 3, 3 or 3, 3 and 6, 6 positions. Thecrystal structure of one of the glycophanes is also described. 相似文献
104.
Ki-Young Choi 《Journal of chemical crystallography》2004,34(9):603-607
A mononuclear complex [Cu(L)(bip)2] (1) (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo [14,4,01.18, 07.12]docosane; bip = 2-benzimidazolepropionate) has been synthesized and structurally characterized by X-ray crystal structure analysis. The crystals are monoclinic P2
1/n with a = 10.2990(2), b = 15.9400(3), c = 11.991(14) Å, = 101.92(7)°, V = 1926(2) Å3, Z = 2. The copper(II) coordination geometry exhibits an axially elongated octahedron with four nitrogen atoms from the macrocycle and two oxygen atoms from the bip ligands. The cyclic voltammogram of 1gives 2 one-electron waves corresponding to CuII/CuIII and CuII/CuI processes. 相似文献
105.
Ki-Young Choi 《Journal of chemical crystallography》2002,32(12):537-540
The complex [Ni(L)](PDC) 2H2O (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[16,4, 01.18,07.12]docosane; PDC = 3,5-pyrazoledicarboxylate) has been synthesized and characterized by X-ray crystallography. It crystallizes in the monoclinic system P21/c with a = 9.739(4) Å, b = 10.491(3) Å, c = 16.884(3) Å, = 97.17(2)°, V = 1711.5(8) Å3, Z = 4. The coordination environment around the nickel(II) ion exhibits a slightly distorted square-plane with four secondary amines of the macrocycle. The title compound is interconnected to give a two-dimensional network through the hydrogen-bonding interactions. 相似文献
106.
A mononuclear complex [Cu(L)(NCS)](ClO4) (1) (L = 1,3,10,12,16,19-hexaazatetracyclo [17,3,1, 112.16,04.9]tetracosane) has been synthesized and structurally characterized by X-ray crystal structure analysis. The crystals are monoclinic P212121 with a = 9.596(1), b = 11.285(1), c = 22.446(2) Å, V = 2430.7(3) Å3, Z = 4. The copper atom is coordinated by two secondary and two tertiary amines of the macrocycle and one nitrogen atom of the thiocynate ligand in a distorted square-pyramidal geometry. The cyclic voltammogram of 1 exhibits two waves of a one-electron transfer corresponding to CuII/CuIII and CuII/CuI processes. 相似文献
107.
David A. Morrison Thomas P. Davis Johan P. A. Heuts Barbara Messerle Alexei A. Gridnev 《Journal of polymer science. Part A, Polymer chemistry》2006,44(21):6171-6189
This work examines cobalt–carbon bond formation between the cobalt (II) macrocycle, (tetrakis(p‐methoxyphenyl)porphyrinato)cobalt (II), (TAP)Co, and a variety of radicals derived from vinyl compounds to facilitate a better understanding of the various factors affecting the cobalt–carbon bond strength in catalytic chain transfer polymerization. The reaction of (TAP)Co with the following vinylic molecules was studied: methacrylonitrile, cyclohexene, methyl methacrylate, styrene, methyl acrylate, vinyl acetate, vinyl benzoate, methyl crotonate, cis‐2‐pentenenitrile, and ethyl α‐hydroxymethacrylate. Different concentrations of each vinylic compound were added to (TAP)Co and 2,2′‐azobis(isobutyronitrile) in CDCl3 at 60 °C. The ratio of Co(III) to Co(II) and the nature of the radical bound to the cobalt macrocycle were determined via nuclear magnetic resonance measurements. Several factors are shown to affect the reaction of the radical and the cobalt (II) species (and hence the strength of the cobalt–carbon bond in the resulting compound). These factors are as follows: the number of pathways by which a radical may be derived from the vinyl compound; the variety of radicals that can be produced from the vinylic molecule; the stability of the radical(s) generated; and the relative propagation rate of the vinyl compound. A discussion on the relevance of this study to the behavior of different monomers in catalytic chain transfer reactions is included. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6171–6189, 2006 相似文献
108.
Ki-Young Choi Moon-Won Kim Ji-Wook Ryu Suk Nam Choi Byung Bin Park Mancheol Suh Il-Hwan Suh 《Journal of chemical crystallography》2001,31(2):81-86
The compound [Ni(L)(2-NO2)]ClO4 (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) has been synthesized and structurally characterized. It crystallizes in the monoclinic system, space group P21/c with a = 26.899(5), b = 8.476(2), c = 23.633(5) Å, = 115.12(13)°, V = 4878.6(17) Å3, and Z = 4. Each nickel(II) ion has a six-coordinated bicapped square-pyramidal geometry with four secondary amines of the macrocycle and two oxygen atoms of the bidentate nitrito group. Electronic spectra and effective magnetic moment of the complex also exhibit a high-spin six-coordinated geometry. 相似文献
109.
Simultaneous determination of trap depth and the ratio of the rate of recombination to that of capture from thermo-luminescence 下载免费PDF全文
Thermo-luminescence (TL) is a kind of luminescence decay measured with
varying temperature. In the process of TL the decay parameter itself
involves the temperature effect of traps. Thus the trap depth is inseparable
from the decay parameter. There are two separate peaks in the TL curve of
ZnS:Cu,Co if the measurement starts from liquid nitrogen temperature. In the
experiment we started from zero Celsius temperature to isolate the deeper
traps. We have proposed and realized three methods for simultaneous
determination of trap depth and decay parameter based on the
quasi-equilibrium model and experimental data. If we treat the case of
kinetic order \alpha =1 as \alpha =2, the error might be as large as
100%. 相似文献
110.
Divergent Solid‐Phase Synthesis of Natural Product‐Inspired Bipartite Cyclodepsipeptides: Total Synthesis of Seragamide A 下载免费PDF全文
Prof. Dr. Hans‐Dieter Arndt Dr. Stefano Rizzo M. Sc. Christina Nöcker Dr. Vijay N. Wakchaure Dr. Lech‐Gustav Milroy B. Sc. Vanessa Bieker Dr. Abram Calderon Dr. Tuyen T. N. Tran Dr. Silke Brand Dr. Leif Dehmelt Prof. Dr. Herbert Waldmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5311-5316
Macrocyclic natural products (NPs) and analogues thereof often show high affinity, selectivity, and metabolic stability, and methods for the synthesis of NP‐like macrocycle collections are of major current interest. We report an efficient solid‐phase/cyclorelease method for the synthesis of a collection of macrocyclic depsipeptides with bipartite peptide/polyketide structure inspired by the very potent F‐actin stabilizing depsipeptides of the jasplakinolide/geodiamolide class. The method includes the assembly of an acyclic precursor chain on a polymeric carrier, terminated by olefins that constitute complementary fragments of the polyketide section and cyclization by means of a relay‐ring‐closing metathesis (RRCM). The method was validated in the first total synthesis of the actin‐stabilizing cyclodepsipeptide seragamide A and the synthesis of a collection of structurally diverse bipartite depsipeptides. 相似文献