Isolation and characterization of cellulose nanoplatelets from the parenchyma cells of <Emphasis Type="Italic">Agave salmiana</Emphasis>

We present a novel nanostructure in the form of cellulose nanoplatelets (CNPs) with an inner array of entangled nanofibrils. The planar structure was isolated from the parenchyma cells of Agave salmiana first using basic pretreatment, then by dissolving lignin and hemicellulose using acid hydrolysis, and finally by modifying the cellulose with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO). The crystallinity index was calculated following the purification process, and it was found that nanocellulose was 30% more crystalline than the raw material. Using transmission electron microscopy, it was found that the nanoplatelets comprise ~2–3 nm long cellulose entangled nanofibrils. In addition, via atomic force microscopy, the morphology of the nanoplatelets was confirmed; they were 90 nm thick for the acid hydrolyzed sample and 70 nm thick for the TEMPO-modified sample; their lateral size varied from a few to hundreds of micrometers, presenting large aspect ratios. Finally, CNPs were isolated and processed into thin paper with a thickness of 100 µm and transmittance of 86%, demonstrating great potential as a transparent film.     

A DFT study of inclusion complexes of the antituberculosis drugs pyrazinamide and isoniazid with cucurbit[7]uril

A photoactive system, (2E)-3-{3-[(Z)-naphthalen-1-yldiazenyl] phenyl} prop-2-enoic acid, was synthesized and incorporated on to beta-cyclodextrin (β-CD) core through esterification of the hydroxyl groups of β-CD with the free carboxyl moiety of the chromophoric system by DCC coupling. The silver nanoparticle was synthesized by the reduction reaction executed on silver acetate in presence of dodecyl amine. The silver nano particles were dispersed in β-CD aggregates modified with photoactive system by phase transfer mechanism. The products were characterized by elemental analysis, melting point determination, UV–visible, FT-IR and NMR (¹H and ¹³C) spectral methods and SEM and TGA-DTG thermal studies. The thermal studies shows that the silver nanoparticle dispersed functionally modified beta cyclodextrin exhibited enhanced thermal stability compared to the functionalised β-CD.     

Enantiopure Cycloiridiated Complexes Bearing a Pentahelicenic N-Heterocyclic Carbene and Displaying Long-Lived Circularly Polarized Phosphorescence

A fused π-helical N-heterocyclic carbene (NHC) system was prepared and examined through its diastereoisomerically pure cycloiridiated complexes. The latter display light-green phosphorescence with unusually long lifetimes and circular polarization that depends on both the helical NHC P/M stereochemistry and the iridium Δ/Λ stereochemistry. These unprecedented features are attributed to extended π conjugation within the helical carbenic ligand and efficient helicene-NHC–Ir interaction.     

Synthesis and properties of alkynethiolate gold(I) complexes

A series of alkynethiolate gold(I) derivatives have been synthesised by the cleavage of 4-monosubstituted 1,2,3-thiadiazoles in the presence of strong bases. The syntheses of the 1.2,3-thiadiazoles with p-cyanophenyl, p-tolyl, 2-thienyl, 3-thienyl and 9,9-dimethylfluoren-2-yl fragments are also described. All the complexes have been characterised by spectroscopic techniques and the complexes [Au(p-CH3-C6H4-C[triple bond]C-S)PPh3], [Au(3-C4H3S-C[triple bond]C-S)PPh3] and PPN[Au(p-CH3-C6H4-C[triple bond]C-S)(C6F5)] by X-ray analysis. The electrochemically polymerizable mononuclear bis(alkynethiolate) gold(I) complex PPN[Au(3-C4H3S-C[triple bond]C-S)2] is also described, including its electropolymerization and electrochemical properties.     

Antimicrobial activity and spectral, magnetic and thermal studies of some transition metal complexes of a Schiff base hydrazone containing a quinoline moiety

A series of new copper(II), cobalt(II), nickel(II), manganese(II), iron(III), and uranyl(VI) complexes of the Schiff base hydrazone 7-chloro-4-(benzylidene-hydrazo)quinoline (HL) were prepared and characterized. The Schiff base behaves as a monobasic bidentate ligand. Mononuclear complexes with the general composition [ML2(Cl)m(H2O)2(OEt)n] x xEtOH (M = Cu(II), Co(II), Ni(II), Mn(II), Fe(III) or UO2(VI); m and n = 0-1; x = 1-3) were obtained in the presence of Li(OH) as a deprotonating agent. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, infrared, electronic spectra, magnetic susceptibility and conductivity measurements. An octahedral geometry was suggested for all the complexes except the Cu(II) and UO2(VI) ones. The Cu(II) complex has a square-planar geometry distorted towards tetrahedral, while the UO2(VI) complex displays its favored heptacoordination. The Schiff base ligand, HL, and its complexes were tested against one strain gram +ve bacteria (Staphylococcus aureus), gram -ve bacteria (Escherichia coli), and Fungi (Candida albicans). The prepared metal complexes exhibited higher antibacterial activities than the parent ligand and their biopotency is discussed.     

Reduction of Carbon Dioxide to Formate at Low Overpotential Using a Superbase Ionic Liquid

A new low‐energy pathway is reported for the electrochemical reduction of CO₂ to formate and syngas at low overpotentials, utilizing a reactive ionic liquid as the solvent. The superbasic tetraalkyl phosphonium ionic liquid [P₆₆₆₁₄][124Triz] is able to chemisorb CO₂ through equimolar binding of CO₂ with the 1,2,4‐triazole anion. This chemisorbed CO₂ can be reduced at silver electrodes at overpotentials as low as 0.17 V, forming formate. In contrast, physically absorbed CO₂ within the same ionic liquid or in ionic liquids where chemisorption is impossible (such as [P₆₆₆₁₄][NTf₂]) undergoes reduction at significantly increased overpotentials, producing only CO as the product.     

Fluorene-based stannylated polymers and their use as recyclable reagents in the Stille reaction

Stannylated polymers based on the polyfluorene backbone have been synthesized and used in the Stille reaction as recyclable reagents, minimizing the generation of toxic tin residues.     

Analytical procedures for the determination of the selective serotonin reuptake inhibitor antidepressant citalopram and its metabolites

The antidepressant citalopram (CIT) is a potent and highly selective serotonin reuptake inhibitor (SSRI) which has been introduced in therapy as a racemic drug. CIT has been used to treat central nervous system affective disorders such as depression, anxiety, obsessive-compulsive disorders, various phobias, borderline personality disorders, bipolar disorders as well as indications wherein inhibition of serotonin reuptake is desired. CIT is demethylated to demethylcitalopram (DCIT) and didemethylcitalopram (DDCIT), which retain considerable activity as SSRIs. Therefore, in recent years, the monitoring of the levels of these analytes in biological fluids for toxicological and therapeutic purposes has been a target worthy of interest. In addition, the differences in activity between CIT enantiomers established the need to assess its behaviour in the field of pharmacological research. It is also necessary to develop analytical methodologies that make it possible to determine the levels of enantiomer concentrations. This review includes most of the published analytical methods for achiral assay of racemic CIT and its metabolites based on high-performance liquid chromatography coupled with UV, fluorescence and mass spectrometry detectors, capillary electrophoresis and gas chromatography with mass spectrometry detectors among others. With regard to the monitoring of enantiomers of CIT and of its metabolites, stereoselective methods based on chiral chromatographic columns, chiral additives in mobile phases and on the derivatization with a chiral reagent are also collected. In addition, different procedures of extraction are mentioned as well as liquid-liquid extraction, solid-phase extraction, solid-phase microextraction, automated online extraction or liquid-phase microextraction in different biological and environmental samples.     

Syntheses and structures of thermally stable diketiminato complexes of gold and copper

While most metallic elements across the Periodic Table form stable chelating β-diketiminato complexes, examples of Au(I) are conspicuous by their absence. We report here the reaction of K[HC(F(3)CC=NR)(2)] with AuCl(PPh(3)) which provides a rare example of a thermally stable gold(I) diketiminato complex, (Ph(3)P)Au[RN=C(CF(3))CH(CF(3))C=NR] [R = 3,5-C(6)H(3)(CF(3))(2)]. The complex is highly fluxional in solution but in the solid state adopts a U-conformation. By contrast, the analogous reaction of K[HC(F(3)CC=NR)(2)] with CuBr(PPh(3))(3) gives the rigid 18-electron chelate complex (Ph(3)P)(2)Cu[κ(2)-HC{(CF(3))C=NR}(2)].