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61.
Balakumar A Lysenko AB Carcel C Malinovskii VL Gryko DT Schweikart KH Loewe RS Yasseri AA Liu Z Bocian DF Lindsey JS 《The Journal of organic chemistry》2004,69(5):1435-1443
A molecular approach to information storage employs redox-active molecules tethered to an electroactive surface. Attachment of the molecules to electroactive surfaces requires control over the nature of the tether (linker and surface attachment group). We have synthesized a collection of redox-active molecules bearing different linkers and surface anchor groups in free or protected form (hydroxy, mercapto, S-acetylthio, and Se-acetylseleno) for attachment to surfaces such as silicon, germanium, and gold. The molecules exhibit a number of cationic oxidation states, including one (ferrocene), two [zinc(II)porphyrin], three [cobalt(II)porphyrin], or four (lanthanide triple-decker sandwich compound). Electrochemical studies of monolayers of a variety of the redox-active molecules attached to Si(100) electrodes indicate that molecules exhibit a regular mode of attachment (via a Si-X bond, X = O, S, or Se), relatively homogeneous surface organization, and robust reversible electrochemical behavior. The acetyl protecting group undergoes cleavage during the surface deposition process, enabling attachment to silicon via thio or seleno groups without handling free thiols or selenols. 相似文献
62.
63.
Heimark L Shipkova P Greene J Munayyer H Yarosh-Tomaine T DiDomenico B Hare R Pramanik BN 《Journal of mass spectrometry : JMS》2002,37(3):265-269
A liquid chromatography/mass spectrometry (LC/MS) method for separation and characterization of ergosterol biosynthetic precursors was developed to study the effect of Posaconazole on sterol biosynthesis in fungi. Ergosterol biosynthetic precursors were characterized from their electron ionization mass spectra acquired by a normal-phase chromatography, particle beam LC/MS method. Fragment ions resulting from cleavage across the D-ring and an abundant M - 15 fragment ion were diagnostic for methyl substitution at C-4 and C-14. Comparison of the sterol profile in control and treated Candida albicans incubations showed depletion of ergosterol and accumulation of C-4 and C-14 methyl-substituted sterols following treatment with Posaconazole. These C-4 and C-14 methyl sterols are known to be incapable of sustaining cell growth. The results demonstrate that Posaconazole exerts its antifungal activity by inhibition of ergosterol biosynthesis. Furthermore, Posaconazole appears to disrupt ergosterol biosynthesis by inhibition of lanosterol 14alpha-demethylase. 相似文献
64.
Martin Proudmore Ji-Feng Ding Richard H. Mobbs Stephen G. Yeates Colin Price Colin Booth 《Journal of polymer science. Part A, Polymer chemistry》1995,33(10):1615-1625
Poly(hexafluoropropylene oxide), poly(HFPO), networks were prepared from functional polymers by end linking via urethane groups. The prepolymers were characterized by NMR spectroscopy and GPC. The networks were characterized by determination of the number of network chains from the shear modulus, and were snown to contain both trifunctional crosslinks and difunctional links. The properties of the networks were investigated by a range of techniques. Compared with fully-fluorinated networks formed via triazine cross-links, investigated previously, the urethane-linked networks were more readily prepared but were poorer elastomers, were less thermally stable, and were less resistant to swelling by common polar solvents. © 1995 John Wiley & Sons, Inc. 相似文献
65.
Selection rules for helicate ligand component self-assembly: steric, pH, charge, and solvent effects
Nitschke JR Schultz D Bernardinelli G Gérard D 《Journal of the American Chemical Society》2004,126(50):16538-16543
The reaction between 1,10-phenanthroline-2,9-dicarboxaldehyde, copper(I), and certain primary amines was found to give quantitatively a dicopper double-helicate product (two of which were crystallographically characterized) by imine self-assembly around Cu(I) templates. The parameters of this reaction were investigated, and important roles were found to be played by (i) the steric bulk of the amine, (ii) the charge of the amine, (iii) the solvent used, and (iv) the pH of the solution. Water was found to allow the broadest range of structures to form, and ligand-component exchange reactions (involving the substitution of an aromatic for an aliphatic amine) were demonstrated to proceed readily in this solvent. 相似文献
66.
A Java applet that predicts solute losses during evaporation from a binary or ternary mixture has been developed which gives good agreement with experiment and can be used to estimate the boiling points of solutes, making use of information which is often collected and then discarded (http://www.ch.cam.ac.uk/magnus/rotavap/). 相似文献
67.
James A. Ballantine Jonathan D. Barton James F. Carter Jeremy P. Davies Keith Smith Geoffrey Stedman Eric E. Kingston 《Journal of mass spectrometry : JMS》1988,23(1):1-5
The mass spectra of a number of aliphatic nitro compounds have been studied using electron Ionization (EI) and a variety of chemical Ionization (CI) techniques in attempts to obtain relative molecular mass information. The use of positive ion ammonia chemical Ionization techniques gave very satisfactory results, providing abundant [M + NH4]+ ions, not only from both primary and secondary nitro compounds, but also from the much more labile tertiary nitro compounds. However, the use of methane and isobutane positive ion CI or EI conditions resulted in facile fragmentation with little relative molecular mass information being made available. Negative ion CI using methane, isobutane or ammonia as moderating gases all gave abundant [M ? 1]? ions with primary and secondary nitro compounds but at much reduced sensitivity. 相似文献
68.
Jack B. Campbell Edward R. Lavagnino Jonathan W. Paschal 《Journal of heterocyclic chemistry》1986,23(3):767-768
The spectral similarities of 10 and 11 substituted 7H-benzimidazo[2,1-a]benz[de]isoquinolin-7-ones hinder the identification of the individual isomers. Preparation of the 13-methyl p-toluenesulfonate salts of these compounds has allowed the assignment by the use of NOE techniques. Saturation of the N-methyl caused an NOE at H-12. The coupling pattern of H-12 then provides identification of the compound. 相似文献
69.
The theoretically estimated dipole moments of indolizine, imidazo[1,2-a]pyridine, imidazo-[1,5-a]pyridine and of pyrazolo[ 1,5-a]pyridine obtained by the CNDO/2 approximation have been compared with the experimental values. The bond angles and bond distances for these polyazaindenes have been estimated. 相似文献
70.
Baber RA Charmant JP Cook AJ Farthing NE Haddow MF Norman NC Orpen AG Russell CA Slattery JM 《Dalton transactions (Cambridge, England : 2003)》2005,(19):3137-3139
Treatment of the diborane(4) compound B(2)(NMe(2))(4) with aniline or 2,6-dimethylaniline results in the primary amido compounds B(2)(NHR)(4)(R = Ph, 2,6-Me(2)C(6)H(3)); subsequent treatment with n-BuLi in toluene in each case affords the first examples of anionic imidodiborates namely Li(4)(thf)(6)B(2)(NPh)(4) and Li(4)(thf)(4)B(2)(N-2,6-Me(2)C(6)H(3))(4); all complexes have been characterised crystallographically. 相似文献