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41.
Vanézia L. Silva Ruy Carvalho Matheus P. Freitas Cláudio F. Tormena Walclée C. Melo 《Structural chemistry》2007,18(5):605-609
Spectrometric and theoretical tools have been employed in this study in order to elucidate the structures of DTPA (diethylenetriaminepentaacetic
acid) complexed to copper and lead. Mass spectrometry allowed determining the 1:1 stoichiometry of metal:ligand, while infrared
spectroscopy demonstrated that both N and O are sites for complexation. 13C NMR analysis showed the existence of free and complexed carboxyl groups, due to a straight singlet at 180.7 ppm (free carboxylic
13C) and to a broad signal at 179.3 ppm (complexed carboxylic 13C, 2
J
Pb…O=C). A distorted NMR signal were observed for the Cu–DTPA carboxyl group, due to the Cu2+ paramagnetism. Based on the spectrometric evidences for the metal–DTPA structures, DFT optimizations were carried out and
an octahedral-like arrangement for the Cu complex and a “shell-like” arrangement for the Pb complex, both hexa-coordinated,
were then proposed for the structures of the titled compounds.
相似文献
Ruy CarvalhoEmail: |
42.
Leandro J. dos Santos Mara R. C. Couri Inácio Luduvico Rosemeire B. Alves Maria A. F. Prado Rossimiriam P. Freitas Gil 《合成通讯》2013,43(18):3059-3066
Five new nitrogen heterocycles, mono‐and disubstituted tetrazoles with potential synthetic and pharmacological interest, were synthesized from α, α‐trehalose via the alkylation of commercial tetrazoles. This method appears to have broad scope with respect to the variations at positions 1 and 2 of tetrazole. 相似文献
43.
New AP Wolff JC Crabtree S Freitas do Santos L Okafo G Lee J Divan K 《Journal of chromatography. A》2001,913(1-2):205-208
We have recently investigated the biodegradation of a number of acidic aromatic compounds that give excellent chromatography using trifluoroacetic acid (TFA) based HPLC methods. Unfortunately HPLC methods using TFA are not usually compatible with detection by negative ion mass spectrometry as TFA suppresses ionisation of the analyte during the electrospray process. We present a preliminary investigation of the use of an anion-exchange micro-membrane suppressor to remove TFA on-line post column with the aim of improvement of mass spectral data using an aromatic acid as an example, Thus LC-MS using a TFA based HPLC method with negative ion mass spectral detection is shown to be possible with good sensitivity. 相似文献
44.
Manuel J.S. Monte Sónia P. Pinto Ana I.M.C. Lobo Ferreira Luísa M.P.F. Amaral Vera L.S. Freitas Maria D.M.C. Ribeiro da Silva 《The Journal of chemical thermodynamics》2012,45(1):53-58
This work reports new experimental thermodynamic results on fluorene. Vapor pressures of both crystalline and liquid phases were measured using a pressure gauge (capacitance diaphragm manometer) and Knudsen effusion methods over a wide temperature range (292.20 to 412.16) K yielding accurate determination of enthalpy and entropy of sublimation and of vaporization. The enthalpy of sublimation was also determined using Calvet microcalorimetry. The enthalpy of fusion was derived from vapor pressure results and from d.s.c. experiments. Static bomb calorimetry was used to determine the enthalpy of combustion of fluorene from which the standard enthalpy of formation in the crystalline phase was calculated. The enthalpy of formation in the gaseous phase was calculated combining the result derived for the crystalline phase with the enthalpy of sublimation. 相似文献
45.
Development of a Simple and Fast Electrochemical Method for Screening and Stoichiometric Determination of Dimenhydrinate 下载免费PDF全文
Jhonys Machado Freitas Thiago da Costa Oliveira Polyana Luiza Silva Denise Tofanello Gimenes Rodrigo Alejandro Abarza Munoz Eduardo Mathias Richter 《Electroanalysis》2014,26(9):1905-1911
Dimenhydrinate (DIM) is a salt composed by the combination of two active pharmaceutical ingredients: diphenhydramine (DIP) and 8‐chlorotheophylline (CTP). In this work, the use of batch injection analysis with multiple pulse amperometric detection (BIA‐MPA) was proposed for the first time for fast stoichiometric determination of DIM. DIP (cation) and CTP (anion) were determined simultaneously in pharmaceutical samples with a simple and fast injection procedure (70 injections h?1). Additional strategies were also proposed for rapid screening of samples containing the DIM salt. By a simple injection of a sample into the BIA system (without using of calibration curve), reliable information about stoichiometry of the DIM salt (1 : 1; DIP:CTP) and presence or absence of interfering species (electroactive) can be achieved. 相似文献
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48.
Chen X Sichelschmidt O Kleemann W Petracic O Binek Ch Sousa JB Cardoso S Freitas PP 《Physical review letters》2002,89(13):137203
The ac susceptibility of a superferromagnetic discontinuous multilayer [Co(80)Fe20(1.4 nm)/Al(2)O3(3 nm)](10) is measured as a function of temperature, frequency, and field amplitude and compared to static and dynamic hysteresis loops. Its properties are successfully mapped onto the predicted [T. Nattermann, V. Pokrovsky, and V. M. Vinokur, Phys. Rev. Lett. 87, 197005 (2001)]] dynamical phase transitions, which link the relaxation, creep, sliding, and switching regimes of pinned domain walls. 相似文献
49.
John?F?StinsEmail author G?Caroline?M?van Baal Tinca?JC?Polderman Frank?C?Verhulst Dorret?I?Boomsma 《BMC neuroscience》2004,5(1):49
Background
There is great interest in appropriate phenotypes that serve as indicator of genetically transmitted frontal (dys)function, such as ADHD. Here we investigate the ability to deal with response conflict, and we ask to what extent performance variation on response interference tasks is caused by genetic variation. We tested a large sample of 12-year old monozygotic and dizygotic twins on two well-known and closely related response interference tasks; the color Stroop task and the Eriksen flanker task. Using structural equation modelling we assessed the heritability of several performance indices derived from those tasks. 相似文献50.