MOFs with Open Metal(III) Sites for the Environmental Capture of Polar Volatile Organic Compounds

Metal–Organic Frameworks (MOFs) with open metal sites (OMS) interact strongly with a range of polar gases/vapors. However, under ambient conditions, their selective adsorption is generally impaired due to a high OMS affinity to water. This led previously to the privilege selection of hydrophobic MOFs for the selective capture/detection of volatile organic compounds (VOCs). Herein, we show that this paradigm is challenged by metal(III) polycarboxylates MOFs, bearing a high concentration of OMS, as MIL-100(Fe), enabling the selective capture of polar VOCs even in the presence of water. With experimental and computational tools, including single-component gravimetric and dynamic mixture adsorption measurements, in situ infrared (IR) spectroscopy and Density Functional Theory calculations we reveal that this adsorption mechanism involves a direct coordination of the VOC on the OMS, associated with an interaction energy that exceeds that of water. Hence, MOFs with OMS are demonstrated to be of interest for air purification purposes.     

In situ application of a cellulose bag and an ion exchanger for differentiation of labile and inert metal species in aquatic systems

This work involved the development and application of a new analytical procedure for in-situ characterization of the lability of metal species in aquatic systems by using a system equipped with a diffusion membrane and cellulose organomodified with p-aminobenzoic acid groups (DM-Cell-PAB). To this end, the DM-Cell-PAB system was prepared by adding cellulose organomodified with p-aminobenzoic acid groups (Cell-PAB) to pre-purified cellulose bags. After the DM-Cell-PAB system was sealed, it was examined in the laboratory. The in-situ application involved immersing the DM-Cell-PAB system in two different rivers, enabling us to study the relative lability of metal species (Cu, Cd, Fe, Mn, and Ni) as a function of time and quantity of exchanger. The procedure is simple and opens up a new perspective for understanding environmental phenomena relating to the complexation, transport, stability, and lability of metal species in aquatic systems rich in organic matter.     

Phonon-assisted excitonic recombination channels observed in DNA-wrapped carbon nanotubes using photoluminescence spectroscopy

By using a sample of DNA-wrapped single-wall carbon nanotubes strongly enriched in the (6,5) nanotube, photoluminescence emissions observed at special excitation energy values were identified with specific mechanisms of phonon-assisted excitonic absorption and recombination processes associated with (6,5) nanotubes, including one-phonon, two-phonon, and some continuous-luminescence processes. Such detailed processes are not separately identified in three-dimensional semiconducting materials. A general theoretical framework is presented to interpret the experimentally observed phonon-assisted processes in terms of excitonic states.     

Clavulanate-selective electrodes - application to pharmaceutical formulations

The construction and assessment of a clavulanate anion-selective electrode and its application to the analysis of pharmaceutical formulations by direct potentiometry are described. The electrode, prepared without inner reference solution, was fabricated by use of a PVC membrane, with bis(triphenyl-phosphoranylidene)ammonium clavulanate as ion-exchanger dissolved in 2-nitrophenyl octyl ether as intermediate solvent and p-t-octylphenol as additive. The response of the electrode was linearly dependent on concentration within the range 2.4 x 10(-3)-1 x 10(-1) mol dm(-3) (ionic strength adjusted to 0.1 mol dm(-3)); the slope of the calibration plot was -59.4+/-0.9 mV decade(-1) and the reproducibility +/-0.6 mV day(-1). The response time was less than 20 s. Relative errors were <3.5% when results from analysis by direct potentiometry were compared with those from the reference method.     

Numerical solution of the two‐phase expansion of a metastable flashing liquid jet using the dispersion‐controlled dissipative scheme

This paper presents a study of the stationary phenomenon of superheated or metastable liquid jets, flashing into a two‐dimensional axisymmetric domain, while in the two‐phase region. In general, the phenomenon starts off when a high‐pressure, high‐temperature liquid jet emerges from a small nozzle or orifice expanding into a low‐pressure chamber, below its saturation pressure taken at the injection temperature. As the process evolves, crossing the saturation curve, one observes that the fluid remains in the liquid phase reaching a superheated condition. Then, the liquid undergoes an abrupt phase change by means of an oblique evaporation wave. Across this phase change the superheated liquid becomes a two‐phase high‐speed mixture in various directions, expanding to supersonic velocities. In order to reach the downstream pressure, the supersonic fluid continues to expand, crossing a complex bow shock wave. The balance equations that govern the phenomenon are mass conservation, momentum conservation, and energy conservation, plus an equation‐of‐state for the substance. A false‐transient model is implemented using the shock capturing scheme: dispersion‐controlled dissipative (DCD), which was used to calculate the flow conditions as the steady‐state condition is reached. Numerical results with computational code DCD‐2D v1 have been analyzed. Copyright © 2009 John Wiley & Sons, Ltd.     

Sulfated meroterpenoids from the Brazilian sponge Callyspongia sp. are inhibitors of the antileishmaniasis target adenosine phosphoribosyl transferase

Three new disulfated meroterpenoids, ilhabelanol (1), ilhabrene (2), and isoakaterpin (3), have been isolated from extracts of the Brazilian marine sponge Callyspongia sp. Isoakaterpin (3) inhibits Leishmania spp. adenosine phosphoribosyl transferase with an IC50 of 1.05 microM. The structures of 1, 2, and 3 were elucidated by analysis of one- and two-dimensional NMR data. Ilhabelanol (1) and ilhabrene (2) both have unprecedented meroterpenoid carbon skeletons.     

Layer-edge conditions for multislab atmospheric radiative transfer problems

We derive nonstandard layer-edge conditions for efficient solution of multislab atmospheric radiative transfer problems. We begin by defining a local radiative transfer problem on the lowermost layer of a multislab model atmosphere and we consider a standard discrete ordinates version of this local problem. We then make use of a recently developed computational method in order to derive layer-edge conditions involving incident, reflected and transmitted radiation. These layer-edge conditions for the lowermost layer are given in terms of inherent optical properties of the layer, the solar zenith angle and the quadrature set used in the discrete ordinates approach. They can be used to increase the efficiency of our computational method in solving practical problems in atmospheric radiative transfer. Moreover, they are amenable to incorporation into other discrete ordinates methods. To illustrate, we report numerical results for two atmospheric model problems.     

Cation environment in polyether complexes based on poly(tetramethylene glycol) doped with zinc and cobalt chlorides

X‐ray absorption spectroscopy [extended X‐ray absorption fine structure (EXAFS) and X‐ray absorption near‐edge structure (XANES)], differential scanning calorimetry, and Raman spectroscopy measurements were performed for a series of liquid polyether/salt systems prepared with poly(tetramethylene glycol) (PTMG) and the copolymer poly(tetramethylene glycol‐co‐ethylene glycol) as matrices and zinc and cobalt chlorides as dopants in the concentration range of n = 30–90, where n is the molar ratio of oxygen to metal cation. According to EXAFS, XANES, and Raman results, even in diluted solutions, these complexes exist mostly as undissociated ZnCl₂ and CoCl₂ species, presenting a weak cation–polymer interaction. EXAFS results indicate that for polymer/ZnCl₂ systems, the nearest metal neighbors are only chlorine atoms. However, for polymer/CoCl₂ samples, oxygen is also observed coordinating the metal. Raman spectra do not support any feature related specifically to the cation–polymer interaction. Nevertheless, for both salts the symmetric stretching vibrations are located in frequencies characteristic of salt in solution, which means that the polymer solvating action is effective. Differential scanning calorimetry data show an increase in the glass‐transition temperature for all polymer/salt systems in relation to the pure polymer samples, a consequence of the increase in the macromolecular chain stiffening produced by the presence of the salt. This result corroborates the existence of polymer–salt interactions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2572–2580, 2001     

Acetogenins from the Leaves of Rollinia laurifolia

From the EtOH extract of the leaves of Rollinia laurifolia Schl . (Annonaceae), a novel acetogenin, rolifolin (= 3‐(9‐{(2R*,5S*)‐5‐[(1S*,4S*)‐1,4‐dihydroxy‐4‐{(2S*,5R*)‐5‐[(1S*)‐1‐hydroxyundecyl]tetrahydrofuran‐2‐yl}butyl]tetrahydrofuran‐2‐yl}‐2,3‐dihydroxynonyl)‐5‐methylfuran‐2(5H)‐one; 1 ) was isolated, together with the known acetogenin annonin‐I ( 2 ). Also, from the corresponding hexane extract, a mixture of rolilaurin ( 3 , a novel compound), uvariamicin‐I ( 4 ), and uvariamicin‐II ( 5 ) was obtained. The structures of compounds 1 – 5 were elucidated by NMR and MS analysis, and relative configurations were established. Compounds 2 and 5 have never been obtained before from Rollinia.