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481.
María Goncalves José Daniel Martínez Mary Lorena Araujo Felipe Brito Giuseppe Lubes Mildred Rodríguez Vito Lubes 《Journal of solution chemistry》2011,40(9):1517-1527
The complex species formed in aqueous solutions (25 °C, I=3.0 mol⋅dm−3 KCl ionic medium) between the V(III) cation and the ligands 6-methylpicolinic acid (MePic, HL), salicylic acid (H2Sal, H2L) and phthalic acid (H2Phtha, H2L) have been studied by potentiometric and spectrophotometric measurements. Application of the least-squares computer program
LETAGROP to the experimental emf(H) data, taking into account the hydrolytic species and hydrolysis constants of V(III), indicates
that under the employed experimental conditions the complexes [VL]2+, [V(OH)L]+, [V(OH)2L], [V(OH)3L]−, [VL2]+, [VL3] and [V2OL4] form in the vanadium(III)–MePic system. Were observed the complexes [VL]+, [VL2]−, [V(OH)L2]2− and [VL3]3− in the vanadium(III)–H2Sal system, and the species [VHL]2+, [VL]+, [V(OH)L], [VHL2], [VL2]−, [V(OH)L2]2−, [V(OH)2L2]3− and [VL3]3− in the vanadium(III)–H2Phtha system. The stability constants of these complexes were determined by potentiometric measurements, and spectrophotometric
measurements were made in order to perform a qualitative characterization of the complexes formed in aqueous solution. 相似文献
482.
Isaida Shiozawa Giuseppe Lubes Mildred Rodríguez Vito Lubes 《Journal of solution chemistry》2011,40(1):17-25
In this work we present results for the speciation of the ternary complexes formed in the aqueous vanadium(III)–dipicolinic
acid and the amino acids cysteine (H2cys), histidine (Hhis), aspartic acid (H2asp) and glutamic acid (H2glu) systems (25 °C; 3.0 mol⋅dm−3 KCl as ionic medium), determined by means of potentiometric measurements. The potentiometric data were analyzed with the
least-squares program LETAGROP, taking into account the hydrolysis of vanadium(III), the acid-base reactions of the ligands,
and the binary complexes formed. Under the experimental conditions (vanadium(III) concentration = 2–3 mmol⋅dm−3 and vanadium(III): dipicolinic acid: amino acid molar ratio 1:1:1, 1:1:2 and 1:2:1), the following species [V(dipic)(H2asp)]+, [V(dipic)(Hasp)], [V(dipic)(asp)]−, [V(dipic)(asp)(OH)]2−, and [V(dipic)(asp)(OH)2]3− were found in the vanadium(III)–dipicolinic acid–aspartic acid system. In the vanadium(III)–dipicolinic acid–glutamic acid
system [V(Hdipic)(H2glu)]2+, [V(dipic)(H2glu)]+, [V(dipic)(Hglu)], [V(dipic)(Hglu)(OH)]−, and [V(dipic)(Hglu)(OH)2]2− were observed. In the vanadium(III)–dipicolinic acid–cysteine system the complexes [V(dipic)(H2cys)]+, [V(dipic)(Hcys)], [V(dipic)(cys)]−, and [V(dipic)(cys)(OH)]2− were present. And finally, in the vanadium(III)–dipicolinic acid–histidine system the complexes [V(Hdipic)(Hhis)]2+, [V(dipic) (Hhis)]+[\mathrm{V}(\mathrm{dipic}) (\mathrm{Hhis})]^{+}, [V(dipic)(his)], [V(dipic)(his)(OH)]−, and [V(dipic)(his)(OH)2]2− were observed. The stability constants of these complexes were determined. The species distribution diagrams as a function
of pH are briefly discussed. 相似文献
483.
A novel flow injection analysis (FIA) system based on liquid-liquid microextraction and fluorimetric determination was developed for the determination of traces of the Zn2+ ion using 5-(8-hydroxy-2-quinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane (L) as a sensitive and selective fluorimetric sensor, with λex = 373 nm and λem = 530 nm, and hexanol as the extracting organic solvent. In the designed FIA system, the phase separation takes place via gravitation forces in the absence of any segmenter. The influence of pH and ionic strength of the solution, amount of ligand, nature of counter ion, volume of organic solvent, extraction time and coil length was investigated. Under optimized experimental conditions, the calibration curve found to be liner over a concentration range of 0.025-4.53 μg mL−1 (R2 = 0.9951) with a limit of detection of 2.3 ng mL−1. The enrichment factor was 45 and relative standard deviation for 7 replicate determinations was 2.43%. The method is very fast and uses low levels of organic solvents. The proposed method was applied successfully to the determination of zinc(II) in human hair, human serum and two inorganic sludge samples. 相似文献
484.
Energy‐dependent dead‐time correction in digital pulse processors applied to silicon drift detector's X‐ray spectra
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Suelen F. Barros Vito R. Vanin Alexandre A. Malafronte Nora L. Maidana Marcos N. Martins 《Journal of synchrotron radiation》2018,25(2):484-495
Dead‐time effects in X‐ray spectra taken with a digital pulse processor and a silicon drift detector were investigated when the number of events at the low‐energy end of the spectrum was more than half of the total, at counting rates up to 56 kHz. It was found that dead‐time losses in the spectra are energy dependent and an analytical correction for this effect, which takes into account pulse pile‐up, is proposed. This and the usual models have been applied to experimental measurements, evaluating the dead‐time fraction either from the calculations or using the value given by the detector acquisition system. The energy‐dependent dead‐time model proposed fits accurately the experimental energy spectra in the range of counting rates explored in this work. A selection chart of the simplest mathematical model able to correct the pulse‐height distribution according to counting rate and energy spectrum characteristics is included. 相似文献
485.
We analyze the efficiency as thermoelectric energy converter of a silicon–germanium alloy with composition and temperature dependent heat conductivity. The dependency on composition is determined by a non-linear regression method (NLRM), while the dependency on temperature is approximated by a first-order expansion in the neighborhood of three reference temperatures. The differences with respect to the case of thermal conductivity depending on composition only are pointed out. The efficiency of the system is analyzed under the assumption that the optimal energy conversion corresponds to the minimum rate of energy dissipated. The values of composition and temperature which minimize such a rate are calculated as well. 相似文献
486.
María del Carmen Razola-Díaz Eduardo Jesús Guerra-Hernndez Beln García-Villanova Vito Verardo 《Molecules (Basel, Switzerland)》2022,27(23)
Fruits and vegetables are a source of a wide range of nutrients, including bioactive compounds. These compounds have great biological activity and have been linked to the prevention of chronic non-communicable diseases. Currently, the food industry is developing new products to introduce these compounds, whereby smoothies are becoming more popular among consumers. The aim of this study was to evaluate the nutritional quality and the polyphenol and vitamin C content of smoothies available on the Spanish market. An evaluation of the nutritional information and ingredients was carried out. The phenolic compounds were determined by HPLC-ESI-TOF-MS; the vitamin C content was quantified using HPLC-UV/VIS; and the antioxidant activity was analyzed by DPPH and FRAP. Among all of the ingredients of the smoothies, coconut and banana have shown a negative impact on the polyphenol content of the smoothies. In contrast, ingredients such as orange, mango, and passion fruit had a positive correlation with the vitamin C content. Moreover, apple and red fruits showed the highest positive correlations with most of the phenolic acids, flavonoids, total phenolic compounds, and antioxidant activities. In addition, a clustering analysis was performed, and four groups were clearly defined according to the bioactive composition determined here. This research is a precious step for the formulation of new smoothies and to increase their polyphenol quality. 相似文献
487.
Andrea Francesca Quivelli Federico Vittorio Rossi Chiara Alario Francesco Sannicol Paola Vitale Joaquín García-lvarez Filippo Maria Perna Vito Capriati 《Molecules (Basel, Switzerland)》2022,27(21)
Dimethindene is a selective histamine H1 antagonist and is commercially available as a racemate. Upon analyzing the synthetic pathways currently available for the industrial preparation of dimethindene, we set up a sustainable approach for the synthesis of this drug, switching from petroleum-based volatile organic compounds (VOCs) to eco-friendly solvents, such as 2-methyltetrahydrofuran (2-MeTHF) and cyclopentyl methyl ether (CPME) belonging to classes 3 and 2, respectively. Beyond decreasing the environmental impact of the synthesis (E-factor: 24.1–54.9 with VOCs; 12.2–22.1 with 2-MeTHF or CPME), this switch also improved the overall yield of the process (from 10% with VOCs to 21–22% with 2-MeTHF or CPME) and remarkably simplified the manual operations, working under milder conditions. Typical metrics applied at the first and second pass, according to the CHEM21 metrics toolkit, were also calculated for the whole synthetic procedure of dimethindene, and the results were compared with those of the classical procedure. 相似文献
488.
Franco Cristiani Francesco A. Devillanova Francesco Isaia Vito Lippolis Gaetano Verani Francesco Demartin 《Heteroatom Chemistry》1993,4(6):571-578
1,4,7-Trithiacyclononane ([9]aneS3) reacts with molecular diiodine in CH2Cl2 to form a 1:1 adduct. The formation constant and the thermodynamic parameters of this adduct have been determined by UV-visible spectra of several solutions at the temperatures of 15, 20, 25, 30, and 35°C. The 13C NMR spectra show that adducts with higher ligand/diiodine molar ratios are formed. Two neutral charge-transfer molecular compounds having formula 2[9]aneS3 · 4I2 ( I ) and [9]aneS3 · 3I2 · ( II ) have been obtained as crystals. The crystals of I are triclinic (a = 8.498(2) Å, b = 13.984(4) Å, c = 14.898(6) Å, α = 65.57(2)°, γ = 89.19(2)°, γ = 81.26(2)°, Z = 2, space group P1; R = 0.025) and contain units formed by two [9]aneS3 molecules connected by a diiodine molecule; one [9]aneS3 binds two other diiodine molecules, while the second binds only one other diiodine molecule. The crystals of II are monoclinic (a = 13.810(2) Å, b = 9.829(4) Å, c = 16.198(6) Å, β = 113.41(2)°, Z = 4, space group P21/c; R = 0.019) and contain molecules of [9]aneS3 binding three diiodine molecules. FT-Raman spectra in the characteristic v(I–I) region, carried out on the solid adducts, are discussed in comparison with the structural parameters. 相似文献
489.
Dr. Giuseppe Dilauro Dr. Cosimo Luccarelli Dr. Andrea F. Quivelli Prof. Paola Vitale Prof. Filippo M. Perna Prof. Vito Capriati 《Angewandte Chemie (International ed. in English)》2023,62(30):e202304720
Advancing the development of perfecting the use of polar organometallics in bio-inspired solvents, we report on the effective generation in batch of organosodium compounds, by the oxidative addition of a C−Cl bond to sodium, a halogen/sodium exchange, or by direct sodiation, when using sodium bricks or neopentylsodium in hexane as sodium sources. C(sp3)-, C(sp2)-, and C(sp)-hybridized alkyl and (hetero)aryl sodiated species have been chemoselectively trapped (in competition with protonolysis), with a variety of electrophiles when working “on water”, or in biodegradable choline chloride/urea or L-proline/glycerol eutectic mixtures, under hydrous conditions and at room temperature. Additional benefits include a very short reaction time (20 s), a wide substrate scope, and good to excellent yields (up to 98 %) of the desired adducts. The practicality of the proposed protocol was demonstrated by setting up a sodium-mediated multigram-scale synthesis of the anticholinergic drug orphenadrine. 相似文献
490.
Dr. Giuseppe Dilauro Dr. Luciana Cicco Prof. Paola Vitale Prof. Filippo Maria Perna Prof. Vito Capriati 《European journal of organic chemistry》2023,26(3):e202200814
A Deep Eutectic Solvent, choline chloride/glycerol (1 : 2 mol mol−1), proved to be an effective and sustainable reaction medium to promote telescoped, one-pot Mizoroki-Heck cross-coupling/reduction processes between 2,3-dihydrofuran or 3,4-dihydro-2H-pyran and several (hetero)aryl halides to easily access valuable 2-(hetero)aryl tetrahydrofuran (THF) or tetrahydropyran derivatives in up to 95 % yield. Notably, the whole transformation takes place under aerobic conditions, in the absence of additional ligands, and with a good substrate scope. The practicability of the method is also exemplified by the sustainable synthesis of two key THF derivatives, which are side chains of pharmacologically relevant inhibitors of Kv1.2 channel. 相似文献