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741.
Mark A. Fox Carlo Nervi Antonella Crivello Andrei S. Batsanov Judith A. K. Howard Kenneth Wade Paul J. Low 《Journal of Solid State Electrochemistry》2009,13(10):1483-1495
The influence of aryl ring substituents X (F, OMe, NMe2, NH2, OH and O−) on the physical and electronic structure of the ortho-carborane cage in a series of C,C′-diaryl-ortho-carboranes, 1-(4-XC6H4)-2-Ph-1,2-C2B10H10 has been investigated by crystallographic, spectroscopic [nuclear magnetic resonance (NMR), UV–vis], electrochemical and
computational methods. The cage C1–C2 bond lengths in this carborane series show small variations with the electron-donating
strength of the substituent X, but there is no evidence of a fully evolved quinoid form within the aryl substituents in the
ground state. In the 11B and 13C NMR spectra, the ‘antipodal’ shift at B12, and the C1 shift correlates with the Hammett σ
p value of the substituent X. The UV–visible absorption spectra of the cluster compounds show marked differences when compared
with the spectra of the analogous substituted benzenes. These spectroscopic differences are attributed to variation in contributions
from the cage orbitals to the unoccupied/virtual orbitals involved in the transitions responsible for the observed absorption
bands. Electrochemical studies (cyclic and square-wave voltammetry) carried out on the diarylcarborane series reveal that
one-electron reduction takes place at the cage in every case with the voltage required for reduction of the cage influenced
by the electron-donating strength of the substituent X, affording a series of carborane radicals with formal [2n + 3] electron
counts.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
742.
Andrea Cappelli Marco Paolino Paolo Anzini Germano Giuliani Salvatore Valenti Marianna Aggravi Alessandro Donati Raniero Mendichi Lucia Zetta Antonella Caterina Boccia Fabio Bertini Filippo Samperi Salvatore Battiato Eugenio Paccagnini Salvatore Vomero 《Journal of polymer science. Part A, Polymer chemistry》2010,48(11):2446-2461
Three methyl end‐capped oligo(ethylene glycol) (MOEG) ethers ( 1b‐d ) and a methoxyderivative ( 1a ) of benzofulvene monomer BF3k were synthesized and induced to polymerize spontaneously by solvent removal to obtain soluble π‐stacked polymers bearing densely grafted MOEG side chains (poly‐ 1b – d ) and model polymer poly‐ 1a. The physicochemical features (e.g., solubility, NMR, MALDI‐TOF, and absorption/emission spectra, as well as MWD, conformation plot, and thermal properties) of the synthesized polymers were compared in a structure‐property relationship study. This approach afforded the following evidence. The structure of poly‐ 1a – d is very similar to that of BF3k , suggesting that the polymerization mechanism is not affected by the presence of the electron‐rich methoxy group or bulkier MOEG side chains. However, the latter appear to be capable of affecting the conformational behavior of the polymer backbone. The solubility of poly‐ 1a – d depends on the number of the oligo(ethylene glycol) monomeric units. In particular, poly‐ 1d , featuring a long MOEG side chain (n = 9), shows an amphiphilic character and is soluble in a number of organic solvents, whereas it interacts with water to give isolated macromolecules in equilibrium with nanosized water‐soluble aggregates. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2446–2461, 2010 相似文献
743.
Ivan Guryanov Dr. Francesca Maria Toma Dr. Alejandro Montellano López Dr. Mauro Carraro Dr. Tatiana Da Ros Dr. Guido Angelini Dr. Eleonora D'Aurizio Dr. Antonella Fontana Prof. Michele Maggini Prof. Maurizio Prato Prof. Marcella Bonchio Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(46):12837-12845
The effect of microwave (MW) irradiation and ionic liquids (IL) on the cycloaddition of azomethine ylides to [60]fullerene has been investigated by screening the reaction protocol with regard to the IL medium composition, the applied MW power, and the simultaneous cooling of the system. [60]Fullerene conversion up to 98 % is achieved in 2–10 min, by using a 1:3 mixture of the IL 1‐methyl‐3‐n‐octyl imidazolium tetrafluoroborate ([omim]BF4) and o‐dichlorobenzene, and an applied power as low as 12 W. The mono‐ versus poly‐addition selectivity to [60]fullerene can be tuned as a function of fullerene concentration. The reaction scope includes aliphatic, aromatic, and fluorous‐tagged (FT) derivatives. MW irradiation of IL‐structured bucky gels is instrumental for the functionalization of single‐walled carbon nanotubes (SWNTs), yielding group coverages of up to one functional group per 60 carbon atoms of the SWNT network. An improved performance is obtained in low viscosity bucky gels, in the order [bmim]BF4> [omim]BF4> [hvim]TF2N (bmim=1‐methyl‐3‐n‐butyl imidazolium; hvim=1‐vinyl‐3‐n‐hexadecyl imidazolium). With this protocol, the introduction of fluorous‐tagged pyrrolidine moieties onto the SWNT surface (1/108 functional coverage) yields novel FT‐CNS (carbon nanostructures) with high affinity for fluorinated phases. 相似文献
744.
Anna Smaniotto Antonella Bertazzo Stefano Comai Pietro Traldi 《Journal of mass spectrometry : JMS》2009,44(3):410-418
High‐molecular‐weight (HMW) coloured compounds called melanoidins are widely distributed, particularly in foods. It has been proposed that they originate through the Maillard reaction, a non‐enzymatic browning reaction, due to the interaction between protein or peptide amino groups and carbohydrates. The melanoidin structure is not definitively known, and they have been generally defined as HMW nitrogen‐containing brown polymers. In order to gain information on the nature of melanoidins, a simple in vitro model was chosen to investigate the products of the reactions between sugars and peptide/proteins. This approach would elucidate whether melanoidin formation is due to the binding of different sugar units to a peptide/protein or vice versa. With this aim, the reactivity of two different peptides, EPK177 and physalaemin, and a low‐molecular‐weight (LMW) protein, lysozyme, was tested towards different saccharides (glucose, maltotriose (MT), maltopentaose and dextran 1000) in aqueous solutions at different temperatures. The incubation mixtures were analysed at different reaction times by MALDI/MS. Furthermore, in order to verify the possible role of sugar pyrolysis products in melanoidin formation, the products arising from the thermal treatment at 200 °C of MT were incubated with lysozyme, and the reaction products were analysed by the same MS approach. The obtained results allowed the establishment of some general views: melanoidins cannot simply originate by reactions of sugar moieties with proteins. In fact, the reaction easily occurs, but it does not lead to any coloured product, as melanoidins have been described to be; melanoidins cannot originate from the thermal degradation products of glycated proteins. In fact, the thermal treatment of glycated lysozyme leads to a severe degradation of the protein with the formation of LMW species, far from the view of melanoidins as HMW compounds; experimental evidence has been gained on the melanoidin formation through reaction of intact protein with the pyrolysis products of MT. This hypothesis has been supported either from MALDI measurements or from spectroscopic data that show an absorption band in the range 300–600 nm, typical of melanoidins. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
745.
Densities of {(1−x)CH3(CH2)n−1OH + xCH3CN} for n=1, 2, 3 or 4 have been determined as a function of composition at 288.15, 293.15, 298.15 and 303.15 K at atmospheric pressure using a vibrating-tube densimeter (Anton Paar DMA 4500, resolution 1×10−5 g cm−3). Excess molar volumes were calculated. The VmE values were negative for acetonitrile–methanol mixtures and sigmoid for acetonitrile–alkanols (C2–C4) mixtures over the complete mole fraction range. VmE values increase in a positive direction with increase in chain length of the alkanols and with the temperature. The Extended Real Associated Solution Model (ERAS-Model) calculations allowing for self-association for the alkanols and complex formation between acetonitrile and alkanols have been used to correlate experimental data. The model is able to reproduce the asymmetrical VmE behavior of the studied systems, although agreement between theoretical and experimental values is less satisfactory for some concentration ranges. 相似文献
746.
747.
Maria Chiara Pietrogrande Francesco Dondi Alessia Ciogli Francesco Gasparrini Antonella Piccin Mauro Serafini 《Journal of chromatography. A》2010,1217(26):4355-4364
In this study, a comparative investigation was performed of HPLC Ascentis® (2.7 μm particles) columns based on fused-core particle technology and Acquity® (1.7 μm particles) columns requiring UPLC instruments, in comparison with Chromolith™ RP-18e columns. The study was carried out on mother and vegetal tinctures of Passiflora incarnata L. on one single or two coupled columns. The fundamental attributions of the chromatographic profiles are evaluated using a chemometric procedure, based on the AutoCovariance Function (ACVF). Different chromatographic systems are compared in terms of their separation parameters, i.e., number of total chemical components (mtot), separation efficiency (σ), peak capacity (nc), overlap degree of peaks and peak purity. The obtained results show the improvements achieved by HPLC columns with narrow size particles in terms of total analysis time and chromatographic efficiency: comparable performance are achieved by Ascentis® (2.7 μm particle) column and Acquity® (1.7 μm particle) column requiring UPLC instruments. The ACVF plot is proposed as a simplified tool describing the chromatographic fingerprint to be used for evaluating and comparing chemical composition of plant extracts by using the parameters D% – relative abundance of the deterministic component – and cEACF – similarity index computed on ACVF. 相似文献
748.
Dugo P Ragonese C Russo M Sciarrone D Santi L Cotroneo A Mondello L 《Journal of separation science》2010,33(21):3374-3385
A total of 92 samples of Sicilian lemon oils (Citrus limon (L.) Burm. f.) produced from September 2008 to June 2009, industrially cold-pressed by different extraction techniques (Brown Oil Extractor and Food Machinery Corporation), were analyzed by GC-flame ionization detector (FID) and GC/MS-LRI to investigate the volatile fraction; by RP-HPLC/PDA to determine the non-volatile components and by enantio-GC-FID to determine the enantiomeric ratios of 12 volatile components. This study provides a detailed investigation on the composition of Sicilian lemon essential oils industrially produced during a productive season, with the aim to recognize quality parameters for the characterization of this product. The results obtained are discussed to evaluate seasonal variation, influence of the extraction techniques, and are compared with those obtained for samples produced during different seasons. 相似文献
749.
Marianna Carbone Antonella Daniele Alessia Ligresti Margherita Gavagnin 《Tetrahedron》2010,66(49):9497-9501
The chemical analysis of a sample of Δ9-THC, which had been stored in an ethanol/propylene glycol solution for 5 years, resulted in the isolation of several hydroxylated Δ9-THC derivatives, the main of which were trans-cannabitriol monoethyl ether (4) and trans-propanediol ethers 7 and 8. cis-Cannabitriol monoethyl ether (5) and the oxidised derivatives 3 and 6 were detected in lesser amounts. The structure elucidation of the unprecedented cannabinoids 3, 5, 7 and 8 was achieved mainly by NMR techniques. Full NMR assignment of compounds 4 and 6 were also made. The detection of cannabitriol (6) and the corresponding solvent-adduct analogues (compounds 4-8) was in agreement with the decomposition mechanisms previously proposed for Δ9-THC. The isolation of the endoperoxide 3 represents indirect evidence of the existence of unstable precursors that were suspected to be intermediates in the non-enzymatic oxidation pathway of Δ9-THC. Both isomers of cannabitriol monoethyl ether exhibited weak affinity at either CB1 (Ki=2.25, 6.30 μM) or CB2 cannabinoid receptors (Ki=1.97, 3.13 μM), the trans isomer always being more potent than the cis isomer. 相似文献