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151.
152.
Mary E. Rampey Carrie E. Halkyard Angela R. Williams April J. Angel Douglas R. Hurst Jessica D. Townsend Anne E. Finefrock Charles F. Beam Shannon L. Studer-Martinez 《Photochemistry and photobiology》1999,70(2):176-183
Abstract. The carbomethoxyhydrazone of 2'-hydroxyacetophenone was trilithiated with excess lithium diisopropylamide and C-acylated with a variety of benzoate esters followed by acid cyclization of the intermediates to 2-(5-aryl-l-car-bomethoxy-lHpyrazol-3-yl)phenols [3-(2-hydroxyphen-yl)-lH-pyrazoles]. The products were characterized by Fourier transform-IR, l H NMR, 13 C NMR, UV-visible absorption and fluorescence. All the derivatives in n -heptane have an absorption maximum at ˜304 nm and an extremely weak (φr = 10 4 ) fluorescence with maxima in the range of 335–460 nm. The broad range of fluorescence maxima and fluorescence quantum yields is attributed to varying contributions of charge transfer that are dependent on both the identity of the substituent and solvent polarity. A phenomenally large Stokes-shifted fluorescence maximum at 620 nm was observed for 2-(l-car-bomethoxy-5-[4-dimethylaminophenyl]-lff-pyrazol-3-y1)phenol in n-heptane and attributed to excited-state intramolecular proton transfer. As a result, competitive excited-state proton/charge transfer properties have been observed in the pyrazoles studied, of which the spectral properties can be fine tuned by substituent as well as solvent effects. 相似文献
153.
Protein electrochemistry using aligned carbon nanotube arrays 总被引:1,自引:0,他引:1
Gooding JJ Wibowo R Liu J Yang W Losic D Orbons S Mearns FJ Shapter JG Hibbert DB 《Journal of the American Chemical Society》2003,125(30):9006-9007
The remarkable electrocatalytic properties and small size of carbon nanotubes make them ideal for achieving direct electron transfer to proteins, important in understanding their redox properties and in the development of biosensors. Here, we report shortened SWNTs can be aligned normal to an electrode by self-assembly and act as molecular wires to allow electrical communication between the underlying electrode and redox proteins covalently attached to the ends of the SWNTs, in this case, microperoxidase MP-11. The efficiency of the electron transfer through the SWNTs is demonstrated by electrodes modified with tubes cut to different lengths having the same electron-transfer rate constant. 相似文献
154.
Miguel A. Camblor María-Jos Díaz-Cabaas Joaquin Perez-Pariente Simon J. Teat William Clegg Ian J. Shannon Philip Lightfoot Paul A. Wright Russell E. Morris 《Angewandte Chemie (International ed. in English)》1998,37(15):2122-2126
Single-crystal X-ray diffraction with synchrotron radiation enabled the structure of microcrystalline SSZ-23 (see drawing on the right), the first zeolite with channels bounded by seven- and nine-membered rings, to be solved. 相似文献
155.
Shannon S. Stahl Jay A. Labinger John E. Bercaw 《Angewandte Chemie (International ed. in English)》1998,37(16):2180-2192
The selective oxidation of alkanes is a topic of considerable interest to both industrial and academic chemists. While the initial discovery occurred more than 25 years ago, new developments in alkane oxidation catalyzed by electrophilic late transition metals have provided important mechanistic insights as well as potentially practical methods for alkane transformations. 相似文献
156.
157.
Nachtergaele Bruno Spitzer Wolfgang Starr Shannon 《Journal of statistical physics》2004,116(1-4):719-738
We study a natural conjecture regarding ferromagnetic ordering of energy levels in the Heisenberg model which complements the Lieb–Mattis Theorem of 1962 for antiferromagnets: for ferromagnetic Heisenberg models the lowest energies in each subspace of fixed total spin are strictly ordered according to the total spin, with the lowest, i.e., the ground state, belonging to the maximal total spin subspace. Our main result is a proof of this conjecture for the spin-1/2 Heisenberg XXX and XXZ ferromagnets in one dimension. Our proof has two main ingredients. The first is an extension of a result of Koma and Nachtergaele which shows that monotonicity as a function of the total spin follows from the monotonicity of the ground state energy in each total spin subspace as a function of the length of the chain. For the second part of the proof we use the Temperley–Lieb algebra to calculate, in a suitable basis, the matrix elements of the Hamiltonian restricted to each subspace of the highest weight vectors with a given total spin. We then show that the positivity properties of these matrix elements imply the necessary monotonicity in the volume. Our method also shows that the first excited state of the XXX ferromagnet on any finite tree has one less than maximal total spin. 相似文献
158.
Jingyang Zhu Benjamin A. Price Jonathan Walker Shannon X. Zhao 《Tetrahedron letters》2005,46(16):2795-2797
Under heterogeneous catalysis, ethyl 2-amino-2-difluoromethyl-4-cyanobutanoate or its Schiff base could be selectively reduced in good yield by hydrogenation to give a diamine, or to form a five-membered ring or a six-membered ring heterocycles. This selectivity is highly dependent on the type of catalysts used. 相似文献
159.
Lu L Rininsland FH Wittenburg SK Achyuthan KE McBranch DW Whitten DG 《Langmuir : the ACS journal of surfaces and colloids》2005,21(22):10154-10159
Herein we describe studies that indicate a cationic conjugated polyelectrolyte shows biocidal activity against gram-negative bacteria (Escherichia coli, E. coli, BL21, with plasmids for Azurin and ampicillin resistance) and gram-positive bacterial spores (Bacillus anthracis, Sterne, B. anthracis, Sterne). These studies were carried out with aqueous suspensions of the conjugated polyelectrolyte, with the polyelectrolyte in supported formats and with samples in which the conjugated polyelectrolyte was coated on the bacteria. The results are interesting in that the biocidal activity is light-induced and appears effective due to the ability of the conjugated polyelectrolyte to form a surface coating on both types of bacteria. The effects observed here should be general and suggest that a range of conjugated polyelectrolytes in different formulations may provide a useful new class of biocides for both dark and light-activated applications. 相似文献
160.
The charge of the upper rim has influences on the binding properties of cavitands in aqueous media. 相似文献