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101.
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103.
Adam M. Graichen Richard W. Vachet 《Journal of the American Society for Mass Spectrometry》2013,24(6):917-925
The gas-phase reactions of a series of coordinatively unsaturated [Ni(L)n]y+ complexes, where L is a nitrogen-containing ligand, with chemical warfare agent (CWA) simulants in a miniature rectilinear ion trap mass spectrometer were investigated as part of a new approach to detect CWAs. Results show that upon entering the vacuum system via a poly(dimethylsiloxane) (PDMS) membrane introduction, low concentrations of several CWA simulants, including dipropyl sulfide (simulant for mustard gas), acetonitrile (simulant for the nerve agent tabun), and diethyl phosphite (simulant for nerve agents sarin, soman, tabun, and VX), can react with metal complex ions generated by electrospray ionization (ESI), thereby providing a sensitive means of detecting these compounds. The [Ni(L)n]2+ complexes are found to be particularly reactive with the simulants of mustard gas and tabun, allowing their detection at low parts-per-billion (ppb) levels. These detection limits are well below reported exposure limits for these CWAs, which indicates the applicability of this new approach, and are about two orders of magnitude lower than electron ionization detection limits on the same mass spectrometer. The use of coordinatively unsaturated metal complexes as reagent ions offers the possibility of further tuning the ion-molecule chemistry so that desired compounds can be detected selectively or at even lower concentrations. Figure
? 相似文献
104.
Novel Copolymers of Styrene and Alkoxy Ring‐Substituted 2‐Cyano‐N,N‐Dimethyl‐3‐Phenyl‐2‐Propenamides
Gregory B. Kharas Xue Tian Adam C. Hermsen Aditi S. Jani Larissa I. Kozij Emira Hadziahmetovic 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10):1485-1492
Electrophilic trisubstituted ethylene monomers, alkoxy ring‐substituted 2‐cyano‐N,N‐dimethyl‐3‐phenyl‐2‐propenamides, RC6H4CH?C(CN)CON(CH3)2 (where R is 2‐OCH3, 3‐OCH3, 4‐OCH3, 2‐OCH2CH3, 3‐OCH2CH3, 4‐OCH2CH2CH3, 4‐OCH2CH2CH2CH3), were synthesized by potassium hydroxide catalyzed Knoevenagel condensation of ring‐substituted benzaldehydes and N,N‐dimethyl cyanoacetamide, and characterized by CHN elemental analysis, IR, 1H‐ and 13C‐NMR. Novel copolymers of the ethylenes and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator, ACBN at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, 1H and 13C NMR, GPC, DSC, and TGA. High Tg of the copolymers in comparison with that of polystyrene indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. The gravimetric analysis indicated that the copolymers decompose in the 300–450°C range. 相似文献
105.
Nathaniel W. Alcock Adam J. Clarke William Errington Ana Maria Josceanu Peter Moore Simon C. Rawle 《Supramolecular chemistry》2013,25(3-4):281-291
Abstract A series of azamacrocycles which have been N-functionalised with pendent pyridylmethyl-(pyCH2-), bipyridylmethyl-(bipyCH2-) and terpyridylmethyl- (terpyCH2-) arms have been synthesised and characterised, and some of their coordination chemistry with transition metal ions is reported. By attaching the pendent-arms at the 5- rather than the 6-position of the py, bipy and terpy, new ligands are generated which can be used to form polynuclear metal complexes in a controlled and systematic fashion. Fluorescent pH and transition metal ion sensors have been developed by reacting the azamacrocyclic N-pendent bipyCH2 arm(s) with cis-[Ru(bipy)2Cl2], to give macrocycles with up to four attached [Ru(bipy)3]2+ groups. That based on 1,4,7-triazacyclononane (9N3), with three attached [Ru(bipy)3]2+ groups, has a first photo excited state pKa of 7.1, and is a useful fluorescent sensor for physiological pH at below micromolar concentrations. The analogous derivative of cyclam (1,4,8,11-tetraazacyclotetradecane) carrying four [Ru(bipy)3]2+ groups has a first photo excited state pKa of 5.7, allowing kinetic and thermodynamic fluorescence studies of metal ion uptake by an azamacrocycle at neutral pH without complications from protonated species. A pre-organised hexadentate tris(2,2′-bipyridyl) chelating ligand, 1,4,7-tris(2′,2″-bipyridyl-5′-ylmethyl)-1,4,7-triazacyclononane (L) has been developed, and crystal structures of mononuclear complexes [M(LH)]3+ (M = Ru, Cu) are reported. In [M(LH)]3+ the azamacrocyclic N-atoms are non-coordinating to M, but have a very high affinity for a single proton trapped in the macrocyclic cavity. An analogous and potentially nonadentate ligand has been developed based on 9N3 with three N-pendent terpyCH2-arms. 相似文献
106.
Kennedy F. Rubert-Nason Liza M. Holeski John J. Couture Adam Gusse Daniel J. Undersander Richard L. Lindroth 《Analytical and bioanalytical chemistry》2013,405(4):1333-1344
Poplar (Populus) and birch (Betula) species are widely distributed throughout the northern hemisphere, where they are foundation species in forest ecosystems and serve as important sources of pulpwood. The ecology of these species is strongly linked to their foliar chemistry, creating demand for a rapid, inexpensive method to analyze phytochemistry. Our study demonstrates the feasibility of using near-infrared reflectance spectroscopy (NIRS) as an inexpensive, high-throughput tool for determining primary (e.g., nitrogen, sugars, starch) and secondary (e.g., tannins, phenolic glycosides) foliar chemistry of Populus and Betula species, and identifies conditions necessary for obtaining reliable quantitative data. We developed calibrations with high predictive power (residual predictive deviations?≤?7.4) by relating phytochemical concentrations determined with classical analytical methods (e.g., spectrophotometric assays, liquid chromatography) to NIR spectra, using modified partial least squares regression. We determine that NIRS, although less sensitive and precise than classical methods for some compounds, provides useful predictions in a much faster, less expensive manner than do classical methods. Graphical abstract
Near-infrared reflectance spectroscopy with calibrations based on modified partial least squares regression can provide quantitative measurements of foliar nitrogen, carbohydrate, tannin, and phenolic glycoside content in poplar and birch 相似文献
107.
A facile one-step synthesis of spiro[4.5]deca-6,9-diene-2,8-dione(1) from p-methoxyphenylacetyl chloride via a Friedel-Crafts acylation followed by ring closure is reported. 相似文献
108.
Alan R. Katritzky Kenneth A. Heck Jianqing Li Adam Wells Catherine Garot 《合成通讯》2013,43(14):2657-2670
α-Lithiated 1-(1-alkenyl)benzotriazoles, generated from the reactions of 1-(1-alkenyl)benzotriazoles with n-BuLi, react with a variety of electrophiles to afford α-substituted 1-(1-alkenyl)benzotriazoles which undergo epoxidation with m-CPBA followed by hydrolysis to give α-hydroxy ketones in good yields. Thus, 1-(1-alkenyl)benzotriazoles behave as α-hydroxyacyl anion equivalents. 相似文献
109.
110.
On doubling metric measure spaces endowed with a strongly local regular Dirichlet form, we show some characterisations of pointwise upper bounds of the heat kernel in terms of global scale-invariant inequalities that correspond respectively to the Nash inequality and to a Gagliardo–Nirenberg type inequality when the volume growth is polynomial. This yields a new proof and a generalisation of the well-known equivalence between classical heat kernel upper bounds and relative Faber–Krahn inequalities or localised Sobolev or Nash inequalities. We are able to treat more general pointwise estimates, where the heat kernel rate of decay is not necessarily governed by the volume growth. A crucial role is played by the finite propagation speed property for the associated wave equation, and our main result holds for an abstract semigroup of operators satisfying the Davies–Gaffney estimates. 相似文献