Biblioteca solidaria en el corazón de África. El Instituto Olvido Ruiz de Valbuena en Burkina Faso

[ES] Félix Pérez Ruiz de Valbuena nos describe cómo es la Biblioteca Olvido, el centro de enseñanza y tecnología más moderno de África Occidental. Creada y financiada por él mismo, de forma altruista, Félix nos explica el motivo que le llevó a crearla, dónde se encuentra, a quiénes sirve y... cuánto durará

Nitazoxanide Cocrystals in Combination with Succinic, Glutaric, and 2,5-Dihydroxybenzoic Acid

Combination of nitazoxanide (NTZ) with a total of 32 cocrystal formers gave cocrystals with succinic acid (NTZ-SUC, 2:1) and glutaric acid (NTZ-GLU, 1:1). Additionally, 2,5-dihydroxybenzoic acid provided a cocrystal solvate with acetonitrile (NTZ-25DHBA-CH₃CN, 1:1:1). All solid phases were characterized by X-ray powder diffraction analysis, IR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and single-crystal X-ray diffraction analysis. Single-crystal X-ray crystallography revealed that NTZ and the carboxylic acid cocrystal formers were linked in all three cocrystals through the same supramolecular heterodimeric synthon, C­(N)­NH···HOOC. Despite having different stoichiometries, the crystal structures of NTZ-SUC and NTZ-GLU showed similarities in the supramolecular organization, both containing two-dimensional layers formed by NTZ molecules, which were further interconnected by single (NTZ-SUC) and homodimeric entities (NTZ-GLU) of the cocrystal former. Basic physical stability tests showed that cocrystals NTZ-SUC and NTZ-GLU are stable at least for one month under standardized temperature/relative humidity stress conditions but decompose within 1 h into the corresponding physical phase mixtures, when exposed to aqueous solutions simulating physiological gastrointestinal conditions. Measurement of the dissolution rates gave small increases of the intrinsic dissolution rate constants when compared with NTZ. Pressure stability tests showed that the cocrystals support higher pressures (at least up to 60 kg/cm²) than NTZ

Nitazoxanide Cocrystals in Combination with Succinic, Glutaric, and 2,5-Dihydroxybenzoic Acid

Combination of nitazoxanide (NTZ) with a total of 32 cocrystal formers gave cocrystals with succinic acid (NTZ-SUC, 2:1) and glutaric acid (NTZ-GLU, 1:1). Additionally, 2,5-dihydroxybenzoic acid provided a cocrystal solvate with acetonitrile (NTZ-25DHBA-CH₃CN, 1:1:1). All solid phases were characterized by X-ray powder diffraction analysis, IR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and single-crystal X-ray diffraction analysis. Single-crystal X-ray crystallography revealed that NTZ and the carboxylic acid cocrystal formers were linked in all three cocrystals through the same supramolecular heterodimeric synthon, C­(N)­NH···HOOC. Despite having different stoichiometries, the crystal structures of NTZ-SUC and NTZ-GLU showed similarities in the supramolecular organization, both containing two-dimensional layers formed by NTZ molecules, which were further interconnected by single (NTZ-SUC) and homodimeric entities (NTZ-GLU) of the cocrystal former. Basic physical stability tests showed that cocrystals NTZ-SUC and NTZ-GLU are stable at least for one month under standardized temperature/relative humidity stress conditions but decompose within 1 h into the corresponding physical phase mixtures, when exposed to aqueous solutions simulating physiological gastrointestinal conditions. Measurement of the dissolution rates gave small increases of the intrinsic dissolution rate constants when compared with NTZ. Pressure stability tests showed that the cocrystals support higher pressures (at least up to 60 kg/cm²) than NTZ

Synthesis of Nanoscale Coordination Polymers in Femtoliter Reactors on Surfaces

In the present work, AFM-assisted lithography was used to perform the synthesis of a coordination polymer inside femtoliter droplets deposited on surfaces. For this, solutions of the metal salt and the organic ligand were independently transferred to adjacent tips of the same AFM probe array and were sequentially delivered on the same position of the surface, creating femtoliter-sized reaction vessels where the coordination reaction and particle growth occurred. Alternatively, the two reagents were mixed in the cantilever array by loading an excess of the inks, and transferred to the surface immediately after, before the precipitation of the coordination polymer took place. The <i>in situ</i> synthesis allowed the reproducible obtaining of round-shaped coordination polymer nanostructures with control over their <i>XY</i> positioning on the surface, as characterized by microscopy and spectroscopy techniques

Mussel-Inspired Hydrophobic Coatings for Water-Repellent Textiles and Oil Removal

A series of catechol derivatives with a different number of linear alkyl chain substituents, and different length, have been shown to polymerize in the presence of aqueous ammonia and air, yielding hydrophobic coatings that present the ability to provide robust and efficient water repellency on weaved textiles, including hydrophilic cotton. The polymerization strategy presented exemplifies an alternative route to established melanin- and polydopamine-like functional coatings, affording designs in which <i>all</i> catechol (adhesive) moieties support specific functional side chains for maximization of the desired (hydrophobic) functionality. The coatings obtained proved effective in the transformation of polyester and cotton weaves, as well as filter paper, into reusable water-repellent, oil-absorbent materials capable of retaining roughly double their weight in model compounds (<i>n</i>-tetradecane and olive oil), as well as of separating water/oil mixtures by simple filtration

Selective Catalytic Deuterium Labeling of Alcohols during a Transfer Hydrogenation Process of Ketones Using D₂O as the Only Deuterium Source. Theoretical and Experimental Demonstration of a Ru–H/D⁺ Exchange as the Key Step

The new complex [(η⁶-<i>p</i>-cym)­RuCl­(κ²-<i>N</i>,<i>N</i>-dmbpy)]­(BF₄) (<i>p</i>-cym = <i>p</i>-cymene; dmbpy = 4,4′-dimethyl-2,2′-bipyridine) is water-soluble and active in the catalytic transfer hydrogenation (TH) of different ketones (cyclohexanone, 2-cyclohexenone, and 3-pentanone) to the corresponding alcohols using aqueous HCOONa/HCOOH as the hydrogen source at pH 4.4. A higher activity was found for the TH of the imine <i>N</i>-benzyl­ideneaniline under the same conditions. Excellent results have been obtained for catalyst recycling. Aqua, formato, and hydrido species were detected by ¹H NMR experiments in D₂O. Importantly, when the catalytic reaction was carried out in D₂O, selective deuteration at the C_α of the alcohols was observed due to a rapid Ru–H/D⁺ exchange, which was also deduced theoretically. This process involves a reversal of polarity of the D⁺ ion, which is transformed into a Ru–D function (“umpolung”). Negligible deuterium labeling was observed for the imine, possibly due to the high activity in the TH process and also to the decrease in the hydrido complex concentration due to the stability of a hydrido-imine intermediate. Both facts should ensure that the TH reaction will compete favorably with the Ru–H/D⁺ exchange. The basic nature of the imine hydrogenation product can also hinder the stated Ru–H/D⁺ exchange. On the basis of DFT calculations, all these hypotheses are discussed. In addition, calculations at this level also support the participation of the stated aqua, formato, and hydrido intermediates in the catalytic reaction and provide a detailed microscopic description of the full catalytic cycle. In the case of the imine TH process, the formation of the hydrido complex (decarboxylation step) is clearly the limiting step of the cycle. On the contrary, in the hydrogenation of cyclohexanone, both decarboxylation and reduction steps exhibit similar barriers, and due to the limitations of the solvent model employed, a definitive conclusion on the rate-determining step cannot be inferred

Core-Level Spectroscopy with Hard and Soft X‑rays on Phosphorus-Containing Compounds for Energy Conversion and Storage

The electronic properties of nine solid phosphorus (P)-containing compounds with varying oxidation states and chemical environments, including GaP(‑III), InP(‑III), red-P(0), H3P(III)O3, Na2H2P2(IV)O6, H3P(V)O4, KH2P(V)O4, Na2HP(V)O4, and InP(V)O4, are investigated using X-ray absorption near-edge structure (XANES) spectroscopy in the hard (P K-edge) and soft X-ray regime (P L2,3-edge). We find shifts in the absorption-edge positions and correlate them with the ligands surrounding the P atom, likely causing a different core–hole interaction screening for different compounds. Complementing the experimental analysis, ab initio many-body calculations of XANES spectra provide insights into the excitonic nature of the observed spectral features and their impact on the electronic structure of the materials. Furthermore, we report on P K-edge XANES measurements on aqueous phosphorus-containing acids, including H3PO3, H3PO4, and their mixtures. At first sight, the spectra of the aqueous acids are similar to those of their solid counterparts. However, close inspection reveals a slight red shift of the absorption edge and the presence of fewer spectral features compared with spectra of the respective solids. Mixtures of aqueous acids display spectral features corresponding to the individual components, indicating the potential for speciation and quantification through fingerprinting