High-throughput aided synthesis of the porous metal-organic framework-type aluminum pyromellitate, MIL-121, with extra carboxylic acid functionalization

A new porous metal-organic framework (MOF)-type aluminum pyromellitate (MIL-121 or Al(OH)[H(2)btec]·(guest), (guest = H(2)O, H(4)btec = pyromellitic acid) has been isolated by using a high-throughput synthesis method under hydrothermal conditions. Its structure was determined from powder X-ray diffraction analysis using synchrotron radiation (Soleil, France) and exhibits a network closely related to that of the MIL-53 series. It is a three-dimensional (3D) framework containing one-dimensional (1D) channels delimited by infinite trans-connected aluminum-centered octahedra AlO(4)(OH)(2) linked through the pyromellitate ligand. Here the organic ligand acts as tetradendate linker via two of the carboxylate groups. The two others remain non-bonded in their protonated form, and this constitutes a rare case of the occurrence of both bonding and non-bonding organic functionalities of the MOF family. The non-coordinated -COOH groups points toward the channels to get them an open form configuration. Within the tunnels are located unreacted pyromellitic acid and water species, which are evacuated upon heating, and a porous MIL-121 phase is obtained with a Brunauer-Emmett-Teller (BET) surface area of 162 m(2) g(-1). MIL-121 has been characterized by IR, thermogravimetry (TG) analyses, and solid state NMR spectroscopy employing a couple of two-dimensional (2D) techniques such as (1)H-(1)H SQ-DQ BABA, (1)H-(1)H SQ-SQ RFDR, (27)Al{(1)H} CPHETCOR and (27)Al MQMAS.     

Palladium and platinum sorption using chitosan-based hydrogels

Two chitosan hydrogels (prepared by NaOH neutralization and by polyphosphate ionotropic gelation) have been tested in the dry state for Pd(II) and Pt(IV) sorption at pH 2. Similar sorption isotherms with maximum sorption capacities close to 190 mg Pd g⁻¹ and 235 mg Pt g⁻¹ were achieved. The sorption mechanism involves electrostatic attraction of the chloro-anionic species onto protonated amine groups; the drastic decrease of sorption capacity with the addition of chloride ions supports this hypothesis. SEM-EDAX analysis suggests that sorption proceeds, in kinetic terms, through a shrinking core mechanism. Metal ions can diffuse throughout all the sorbent volume. The main differences between the sorbents are revealed by kinetics. The hydrogels prepared by ionotropic gelation in polyphosphate (C-PPh) allows reaching equilibrium much faster than the hydrogels prepared by the neutralization process (C-NaOH). While for C-PPh sorbent the chemical reaction rate seems to control sorption profiles, in the case of C-NaOH a combination of mechanisms including intraparticle diffusion resistance controls uptake kinetics. Metal desorption from loaded sorbents is possible using thiourea alone or in association with HCl solutions. The recycling of the sorbents is possible but for a limited number of cycles.     

Determination of calcium, magnesium, sodium, and potassium in foodstuffs by using a microsampling flame atomic absorption spectrometric method after closed-vessel microwave digestion: method validation

This paper describes a validation process in compliance with the NFIEN ISO/IEC 17025 standard for the determination of the macrominerals calcium, magnesium, sodium, and potassium in foodstuffs by microsampling with flame atomic absorption spectrometry after closed-vessel microwave digestion. The French Standards Commission (Agence Francaise de Normalisation) standards NF V03-110, NF EN V03-115, and XP T-90-210 were used to evaluate this method. The method was validated in the context of an analysis of the 1322 food samples of the second French Total Diet Study (TDS). Several performance criteria (linearity, LOQ, specificity, trueness, precision under repeatability conditions, and intermediate precision reproducibility) were evaluated. Furthermore, the method was monitored by several internal quality controls. The LOQ values obtained (25, 5, 8.3, and 8.3 mg/kg for Ca, Mg, Na, and K, respectively) were in compliance with the needs of the TDS. The method provided accurate results as demonstrated by a repeatability CV (CVr) of < 7% and a reproducibility CV (CVR) of < 12% for all the elements. Therefore, the results indicated that this method could be used in the laboratory for the routine determination of these four elements in foodstuffs with acceptable analytical performance.     

Highly diastereo- and enantioselective organocatalytic michael addition of α-ketoamides to nitroalkenes

The first organocatalytic enantio- and diastereoselective conjugate addition of α-ketoamides to nitroalkenes has been achieved using a bifunctional amino thiourea catalyst. In this new approach, the substrate amide proton plays a critical role in the formation of the Michael anti-adducts in high yields and high stereoselectivities. To illustrate the high synthetic potential of this methodology, the diastereo- and enantioselective synthesis of a hexasubstituted cyclohexane via a Michael-Michael-Henry cascade reaction is described.     

Stability of matter–wave soliton in a time-dependent complicated trap

We examine the possibility to generate localized structures in effectively one-dimensional Gross–Pitaevskii with a time-dependent scattering length and a complicated potential. Through analytical methods invoking a generalized lens-type transformation and the Darboux transformation, we present the integrable condition for the Gross–Pitaevskii equation and obtain the exact analytical solution which describes the modulational instability and the propagation of bright solitary waves on a continuous wave background. The dynamics and stability of this solution are analyzed. Moreover, by employing the extended tanh-function method we obtain the exact analytical solutions which describes the propagation of dark and other families of solitary waves.     

Cyclometallation of arylimines and nitrogen-containing heterocycles via room-temperature C-H bond activation with arene ruthenium(ii) acetate complexes

The reaction of [RuCl(2)(p-cymene)](2) with arylimines and 4 equiv. of KOAc in methanol at room temperature produces stable (N^C)-cyclometallated ruthenium(ii) complexes via C-H bond activation/deprotonation. This method can be applied also to nitrogen-containing molecules: N-phenylpyrazole, 2-phenyl-2-oxazoline and benzo[h]quinoline. N-Phenyl-pyrazole, [RuCl(2)(p-cymene)](2) and diphenylacetylene directly lead to alkyne insertion into the metallacycle C-Ru bond.     

Synthetic studies toward C-glucosidic ellagitannins: a biomimetic total synthesis of 5-O-desgalloylepipunicacortein A

C-glucosidic ellagitannins constitute a subclass of bioactive polyphenolic natural products with strong antioxidant properties, as well as promising antitumoral and antiviral activities that are related to their capacity to interact with both functional and structural proteins. To date, most synthetic efforts toward ellagitannins have concerned glucopyranosic species. The development of a synthetic strategy to access C-glucosidic ellagitannins, whose characteristic structural feature includes an atropoisomeric hexahydroxydiphenoyl (HHDP) or a nonahydroxyterphenoyl (NHTP) unit that is linked to an open-chain glucose core by a C-aryl glucosidic bond, is described herein. The total synthesis of the biarylic HHDP-containing 5-O-desgalloylepipunicacortein?A (1?β) was achieved by either using the natural ellagic acid bis-lactone as a precursor of the requested HHDP unit or by implementing an atroposelective intramolecular oxidative biarylic coupling to forge this HHDP unit. Both routes converged in the penultimate step of this synthesis to enable a biomimetic formation of the key C-aryl glucosidic bond in the title compound.     

Determination of trehalose-6-phosphate in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> seedlings by hydrophilic-interaction liquid chromatography–mass spectrometry

A hydrophilic-interaction chromatography (HILIC) method coupled to electrospray ionization mass spectrometry (ESI-MS) was developed for the determination of trehalose-6-phophate (Tre6P) in Arabidopsis thaliana seedlings. The method was optimized for MS detection and separation of Tre6P from its isomers, such as sucrose-6-phosphate, by testing eluent pH, type of organic solvent and alkalinizer, and gradient conditions. Tre6P could be resolved from matrix components within 28 min by using a water–acetonitrile gradient (0.2 ml/min) at pH 12 with piperidine as alkalinizer. The method was validated for concentrations between 25 and 4,000 nM Tre6P in A. thaliana seedling extracts. Seedlings were extracted with consecutive liquid-liquid and solid-phase extractions, and analyzed with HILIC-MS. Obtained accuracy (80–120 %) and precision (<24 %) demonstrated the suitability of HILIC-MS for determining Tre6P level variations in plants. The limit of detection (LOD) was 3.5 nM Tre6P in extracts corresponding to 4.1 pmol.g⁻¹ fresh plant weight (FW). This is a considerable improvement with respect to anion-exchange chromatography (AEC)-MS (40 nM) and capillary electrophoresis-MS (80 nM). Furthermore, HILIC-MS analysis times were shorter than with AEC-MS (30 and 60 min, respectively). The applicability of the HILIC-MS method was demonstrated by the analysis of extracts from seedlings grown on medium containing 100 mM sorbitol or trehalose, resulting in mean Tre6P concentrations of 0.2 and 1.9 nmol.g⁻¹ FW, respectively. Similar concentrations were found with AEC-MS. HILIC-MS was also evaluated at a high flow rate (2.0 ml/min). This high-speed method resolved the Suc6P and Tre6P peaks within 3 min yielding a detection limit of 1.3 nM Tre6P.     

Three-dimensional direct femtosecond laser writing of second-order nonlinearities in glass

We demonstrate that direct femtosecond laser writing in silver-containing zinc and gallium phosphate glass enables generation of three-dimensional (3D) optical second-order nonlinear microstructures having an χ(2) value about 2.5 times that of quartz. The proposed physical model involves photo-reduction, photo-dissociation, and migration of silver species within the glass matrix. 3D laser-written second-order nonlinear structures could become a new class of nonlinear optical components.