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排序方式: 共有401条查询结果,搜索用时 15 毫秒
391.
Alberto EE Rossato LL Alves SH Alves D Braga AL 《Organic & biomolecular chemistry》2011,9(4):1001-1003
The synthesis and antimicrobial profile of imidazolium ionic liquids containing selenium are described herein. Minimum inhibitory concentration revealed that these compounds are especially active against algae, and their activity is modulated by substituents attached to the selenium moiety as well as by the counterion. 相似文献
392.
In recent years, there has been an increasing application of chiral selenium compounds as ligands in metal-catalyzed enantioselective transformations. One of the most important challenges in this field is the development of new chiral complexes (catalyst) generated from the reaction between a metal and appropriate chiral selenium-containing compounds (ligand). The vast majority of these ligands are easily synthesized in a few high-yielding synthetic steps, starting from readily available chiral amino alcohols. In this context, the advantages of using these compounds will be discussed, mainly with regard to their easy accessibility, modular nature and the formation of strong bonds with soft or, more rarely, hard metals. Important selective contributions within the field of chiral selenium complexes are examined, according to their applications. As final remarks, future developments and perspectives of the field are discussed. 相似文献
393.
Thiago O. Carvalho Ana E. B. Matias Lilian R. Braga Sheila M. Evangelista Alexandre G. S. Prado 《Journal of Thermal Analysis and Calorimetry》2011,106(2):475-481
Chitosan microspheres were applied to remove the pollutants diclofenac and dipyrone from water. Adsorption studies were adjusted
to Langmuir equation. The maximum number of adsorbed moles gave 5.25 × 10−4 and 4.83 × 10−4 mol of diclofenac and dipyrone, respectively, per gram of chitosan microspheres. The interactions in solid/liquid interface
were calorimetrically followed and gave endothermic values: +22.1 ± 1.3 and +48.7 ± 1.5 kJ mol−1, respectively, for the same sequence. Both Gibbs energy values were negative. Adsorption processes were accompanied by an
increase in entropy. These interactions were studied by FTIR spectroscopy which showed a strengthening of the CN stretching
(dislocated shifts from 1,325 to 1,371 cm−1) related to a weakening of the NH stretch caused by the interaction with drugs. 相似文献
394.
Alessandrini L Braga D Jaafari A Miozzo L Mora S Silvestri L Tavazzi S Yassar A 《The journal of physical chemistry. A》2011,115(3):225-231
The polarized UV-visible absorption spectra of dibenzo[d,d']thieno[3,2-b;4,5-b']dithiophene single crystals are reported and interpreted to definitively attribute the observed bands and their polarizations. The results provide information on the intermolecular interactions and on the aggregation in the condensed phase, which can be of either herringbone- or H-type, depending on the electronic transition taken into considerations, with consequences on the order and polarization of the absorption bands. A relatively easy method is also discussed to obtain information on the structural/morphological properties of different types of samples, including thin films, which have been recently proposed for high-performance organic film-effect transistors for their high ionization potential and photostability. 相似文献
395.
Braga D d'Agostino S D'Amen E Grepioni F 《Chemical communications (Cambridge, England)》2011,47(18):5154-5156
A new silver(I) complex with 1-phenyl-3-(quinolin-5-yl)urea has been prepared, acting as a supramolecular supergelator in the presence of polar solvents. In open vials temperature dependent, reversible gel-to-xerogel transition is observed, while in sealed vials direct crystallization of four polymorphs of the same gelling compound is achieved, depending on the gelling solvent. 相似文献
396.
Susana S. Braga Isabel S. GonÇalves Paulo Ribeiro-Claro André D. Lopes Martyn Pillinger José J.C. Teixeira-Dias 《Supramolecular chemistry》2013,25(4):359-366
Inclusion compounds have been prepared comprising g -cyclodextrin (CD) molecules as the host and half-sandwich cyano complexes of iron as the guests. High yields of crystalline one-to-one adducts were obtained by treatment of CpFe(CO) 2 CN and K[CpFe(CO)(CN) 2 ] with g -CD. In the case of CpFe(dppe)CN [dppe=bis(diphenylphosphine)ethane], a non-stoichiometric product is obtained and it is evident that the organometallic guests are easily liberated from the host cavities. The products were characterized in the solid-state by elemental analysis, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), FTIR and CP MAS NMR ( 13 C, 31 P) spectroscopy. Additional information concerning the possible structure of the inclusion compounds was obtained from ab initio calculations using a two-layer approximation. The best organometallic- g -CD interaction is obtained with deep inclusion of the cyclopentadienyl ring, a geometry that is not possible in the case of the CpFe(dppe)CN system due to the size and orientation of the dppe ligand. 相似文献
397.
José M. Braga 《Acta Appl Math》1999,55(3):313-333
In this paper we generalize the classical Jacobson–Bourbaki correspondence for field extensions to K-vector space extensions (K a field). Namely, for such extensions, we state and prove a correspondence theorem – the Jacobson–Bourbaki correspondence with parameters. Some examples are provided. 相似文献
398.
Fabíola F. G. Rodrigues Aline A. Boligon Irwin R. A. Menezes Fbio F. Galvo-Rodrigues Gerson J. T. Salazas Carla F. A. Nonato Nara T. T. M. Braga Fabrina M. A. Correia Germana F. R. Caldas Henrique D. M. Coutinho Abolghasem Siyadatpanah Bonglee Kim Jos G. M. Costa Adriana R. C. Barros 《Molecules (Basel, Switzerland)》2021,26(24)
The increase in antibiotic resistance and the emergence of new bacterial infections have intensified the research for natural products from plants with associated therapy. This study aimed to verify the antibacterial and antioxidant activity of crude extracts of the genus Plectranthus species, being the first report on the modulation of aminoglycosides antibiotic activity by Plectranthus amboinicus extracts. The chemical composition was obtained by chemical prospecting and High-Performance Liquid Chromatography with diode arrangement detector (HPLC/DAD). The antibacterial activities of the extracts alone or in association with aminoglycosides were analyzed using the microdilution test. The antioxidant activity was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging. The phytochemical prospection allowed the flavonoids, saponins, tannins and triterpenoids to be identified. Quercetin, rutin, gallic acid, chlorogenic acid, caffeic acid, catechin, kaempferol, glycosylated kaempferol, quercitrin, and isoquercitrin were identified and quantified. The principal component analysis (PCA) observed the influence of flavonoids and phenolic acids from Plectranthus species on studied activities. Phytochemical tests with the extracts indicated, especially, the presence of flavonoids, confirmed by quantitative analysis by HPLC. The results revealed antibacterial activities, and synergistic effects combined with aminoglycosides, as well as antioxidant potential, especially for P. ornatus species, with IC50 of 32.21 µg/mL. Multivariate analyzes show that the inclusion of data from the antioxidant and antibacterial activity suggests that the antioxidant effect of these species presents a significant contribution to the synergistic effect of phytoconstituents, especially based on the flavonoid contents. The results of this study suggest the antibacterial activity of Plectranthus extracts, as well as their potential in modifying the resistance of the analyzed aminoglycosides. 相似文献
399.
400.