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991.
Pardo E Ruiz-García R Cano J Ottenwaelder X Lescouëzec R Journaux Y Lloret F Julve M 《Dalton transactions (Cambridge, England : 2003)》2008,(21):2780-2805
The aim and scope of this review is to show the general validity of the 'complex-as-ligand' approach for the rational design of metallosupramolecular assemblies of increasing structural and magnetic complexity. This is illustrated herein on the basis of our recent studies on oxamato complexes with transition metal ions looking for the limits of the research avenue opened by Kahn's pioneering research twenty years ago. The use as building blocks of mono-, di- and trinuclear metal complexes with a novel family of aromatic polyoxamato ligands allowed us to move further in the coordination chemistry-based approach to high-nuclearity coordination compounds and high-dimensionality coordination polymers. In order to do so, we have taken advantage of the new developments of metallosupramolecular chemistry and in particular, of the molecular-programmed self-assembly methods that exploit the coordination preferences of metal ions and specifically tailored ligands. The judicious choice of the oxamato metal building block (substitution pattern and steric requirements of the bridging ligand, as well as the electronic configuration and magnetic anisotropy of the metal ion) allowed us to control the overall structure and magnetic properties of the final multidimensional nD products (n = 0-3). These species exhibit interesting magnetic properties which are brand-new targets in the field of molecular magnetism, such as single-molecule or single-chain magnets, and the well-known class of molecule-based magnets. This unique family of molecule-based magnetic materials expands on the reported examples of nD species with cyanide and related oxalato and dithiooxalato analogues. Moreover, the development of new oxamato metal building blocks with potential photo or redox activity at the aromatic ligand counterpart will provide us with addressable, multifunctional molecular materials for future applications in molecular electronics and nanotechnology. 相似文献
992.
A general NMR spectroscopy protocol for determination of absolute configuration of thiols, that includes the introduction of new aryl-tert-butoxyacetic acids as chiral derivatizing agents (CDAs), is described. 相似文献
993.
Reig N Calaf RE Messeguer A Morató A Escabros J Gelpí E Abian J 《Journal of mass spectrometry : JMS》2007,42(4):527-541
In 1981 Spain went through a unique epidemic associated with a food-borne vector, affecting more than 20,000 people with over 800 deaths, which came to be known as the Toxic Oil Syndrome (TOS). Early epidemiological studies showed a link between this illness and the ingestion of rapeseed oil denatured with 2% aniline. This oil, originally aniline-denatured for industrial use, was fraudulently processed in an attempt to remove free aniline, and marketed as edible oil. Fatty acid anilides (FAA), monoesters and diesters of 3-(N-phenylamino)-1,2-propanediol (PAP) are present in oil samples as they arise in the refining process from reactions of aniline with constituent fatty acids and triglycerides of the oil matrix and are the only extraneous compounds found in these samples. To expand the search for the causative agents in TOS-associated oils and to look for new aniline-related compounds, an exhaustive characterization of laboratory-processed oils was undertaken. These oils, in the presence of aniline doped with 14C labelled aniline, were submitted to the laboratory conditions required for the generation of PAPs and FAAs. Laboratory-generated oil samples were submitted to a liquid-liquid extraction procedure to remove the unreacted aniline. The extract was processed by double solid-phase extraction to improve detection limits for minor amine-containing compounds in oils. The extracts enriched in aniline derivatives were submitted to on-line HPLC-UV-APCI-MS. Using two-dimensional ion maps, the components of several families of derivatives were readily identified. Additionally, the extracts were also fractionated by HPLC-UV and the fractions were analyzed by HPLC-APCI-MS/MS to obtain structural information. Standards of some of these compounds were synthesized and analyzed to confirm the results. A total of 115 aniline derivatives from 9 aniline-related families were identified in these oil samples. These included fatty acid anilides and an extensive array of phenylaminopropanediol esters distributed in eight major compound classes. 相似文献
994.
Mousavipour SH Fernández-Ramos A Meana-Pañeda R Martínez-Núñez E Vázquez SA Ríos MA 《The journal of physical chemistry. A》2007,111(4):719-725
Direct-dynamics canonical variational transition-state theory calculations with microcanonically optimized multidimensional transmission coefficient (CVT/muOMT) for tunneling were carried out at the MPWB1K/6-31+G(d,p) level to study the [1,7] sigmatropic hydrogen rearrangement in 7-methylocta-1,3(Z),5(Z)-triene. This compound has seven conformers, of which only one leads to products, although all of them have to be included in the theoretical treatment. The calculated CVT/muOMT rate constants are in good agreement with the available experimental data. To try to understand the role of tunneling in the hydrogen shift reaction, we have also calculated the thermal rate constants for the monodeuterated compound in the interval T = 333.2-388.2 K. This allowed us to evaluate primary kinetic isotope effects (KIEs) and make a direct comparison with the experiment. Our calculations show that both the large measured KIE and the large measured difference in the activation energies between the deuterated and root compounds are due to the quantum tunneling. The tunneling contribution to the KIE becomes noticeable only when the coupling between the reaction coordinate and the transverse modes is taken into account. Our results confirm previous experimental and theoretical works, which guessed that the obtained kinetic parameters pointed to a reaction with an important contribution due to tunneling. The above conclusion would be essentially valid for the case of the [1,7] hydrogen shift in previtamin D3 because of the similarity to the studied model system. 相似文献
995.
Cristina Negro Paula Escamilla Rosaria Bruno Dr. Jesus Ferrando-Soria Dr. Donatella Armentano Dr. Emilio Pardo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(24):e202200034
The combination of high crystallinity and rich host-guest chemistry in metal-organic frameworks (MOFs), have situated them in an advantageous position, with respect to traditional porous materials, to gain insight on specific weak noncovalent supramolecular interactions. In particular, sulfur σ-hole interactions are known to play a key role in the biological activity of living beings as well as on relevant molecular recognitions processes. However, so far, they have been barely explored. Here, we describe both how the combination of the intrinsic features of MOFs, especially the possibility of using single-crystal X-ray crystallography (SCXRD), can be an extremely valuable tool to gain insight on sulfur σ-hole interactions, and how their rational exploitation can be enormously useful in the efficient removal of harmful organic molecules from aquatic ecosystems. Thus, we have used a MOF, prepared from the amino acid L-methionine and possessing channels decorated with −CH2CH2SCH3 thioalkyl chains, to remove a family of organic dyes at very low concentrations (10 ppm) from water. This MOF is able to efficiently capture the four dyes in a very fast manner, reaching within five minutes nearly the maximum removal. Remarkably, the crystal structure of the different organic dyes within MOFs channels could be determined by SCXRD. This has enabled us to directly visualize the important role sulfur σ-hole interactions play on the removal of organic dyes from aqueous solutions, representing one of the first studies on the rational exploitation of σ-hole interactions for water remediation. 相似文献
996.
Albert Ferrer‐Ugalde Emilio José Juárez‐Pérez Francesc Teixidor Clara Viñas Dr. Rosario Núñez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(50):17021-17030
Novel polyhedral oligomeric silsesquioxanes (POSS) or octasilsesquioxanes with carboranyl–styrene fragments attached to each corner are described. These compounds have been synthesized by olefin‐metathesis reactions between octavinylsilsesquioxane and carboranyl–styrene compounds that possess different substituents (Ph, Me, or H). In all cases, these reactions, which were catalyzed by the Grubbs catalyst, are highly regioselective and yield exclusively the E isomers. The existence of the carborane cage in the POSS structure induces a remarkable thermal stability in these compounds. After combustion at 1000 °C, these carboranyl–POSS compounds exhibit a mass loss lower than 10 %. The UV/Vis absorption data of these carboranyl–POSS compounds shows a slight bathochromic shift with respect to the carboranyl–styrene monomers, with an absorption maximum around 262 nm. Nevertheless, important differences in the emission spectra of the carboranyl–POSS compounds with regard to their carboranyl–styrene precursors are observed; the phenyl‐o‐carborane‐containing POSS compound exhibits the highest fluorescence intensity (ΦF=44 %), whereas for the POSS compound bearing the methyl substituent, and for the unsubstituted o‐carborane clusters, the fluorescence intensity is much lower (ΦF=9 and 2 %, respectively). This is precisely the reverse of what occurs with the monomers, in which the unsubstituted o‐carboranyl–styrene compound exhibits the highest ΦF, and a quenching of the fluorescence is observed in the phenyl‐o‐carboranyl–styrene compound. In addition, a large red shift of around 100 nm is observed for the POSS compounds with respect to their precursors. These experimental results can only be accounted for by the spatial ordering induced by the POSS core that eases interactions, which otherwise would not occur. These results have been confirmed by time‐dependent density functional theory (TDDFT) calculations that exclude a photoinduced electron transfer (PET) process in the POSS compounds. 相似文献
997.
998.
999.
David M. Lavenson Emilio J. Tozzi Michael J. McCarthy Robert L. Powell Tina Jeoh 《Cellulose (London, England)》2011,18(6):1543-1554
Cellulosic biomass is recalcitrant to enzymatic hydrolysis which greatly reduces the efficiency of biofuels production. Specifically,
the lignin component of biomass is thought to provide non-productive binding sites for glycosyl hydrolases, effectively disabling
the enzymes from completing further digestion. A thorough understanding of the adsorption rates of protein molecules on celluloses—especially
lignocelluloses—is crucial to improving the cyclic steps of adsorption, diffusion, and reaction. We use magnetic resonance
imaging (MRI) to detect concentrations of bovine serum albumin (BSA) in equilibrium with various cellulose substrates, including
delignified and acid-treated lignocellulosic substrates. BSA is believed to be an effective adsorption blocker during enzymatic
hydrolysis of lignocellulosics, and has been correlated with an increase in reaction yield. We found BSA to have little adsorption
onto the chosen cellulose substrates in the low concentration range studied. Ultraviolet (UV) absorption measurements of reaction
supernatants at 280 nm were used to confirm the MRI results for each of the substrate types. The advantages of the MRI technique
are compared with that of the traditional UV measurement. 相似文献
1000.