Hexagonal mesoporous silica modified with copper phthalocyanine as a photocatalyst for pesticide 2,4-dichlorophenoxiacetic acid degradation

A new mesoporous catalyst was prepared by the reaction between 3-aminopropyltrimethoxisylane and Cu(II)-hexadecafluorophthalocyanine, followed by co-condensation of tetraethylorthosilicate around a micelle formed by n-dodecylamine. The surfactant was removed from the pores by continuous extraction with ethanol, giving the Si-CuF16Pc catalyst. This catalyst was characterized by SEM, FTIR, TGA, 29Si NMR, N2 adsorption and X-ray diffraction. SEM images confirmed that the catalyst material is formed by nanoaggregates with a diameter of 100 nm. N2 adsorption isotherms showed that Si-CuF16Pc has a surface area of approximately 200 m2 g(-1) and a porous diameter of 7.7 nm, characterizing the mesoporosity of this product. This novel material shows an excellent photocatalytic activity, degrading almost 90% of 2,4-dichlorophenoxyacetic acid (2,4-D) up to 30 min, while only approximately 40% of photodegradation was obtained in its absence.     

Using phospholipid Langmuir and Langmuir-Blodgett films as matrix for urease immobilization

The immobilization of enzymes in organized two-dimensional matrices is a key requirement for many biotechnological applications. In this paper, we used the Langmuir-Blodgett (LB) technique to obtain controlled architectures of urease immobilized in solid supports, whose physicochemical properties were investigated in detail. Urease molecules were adsorbed at the air-water interface and incorporated into Langmuir monolayers of the phospholipid dipalmitoyl phosphatidyl glycerol (DPPG). Incorporation of urease made DPPG monolayers more flexible and caused the reduction of the equilibrium and dynamic elasticity of the film. Urease and DPPG-urease mixed monolayers could be transferred onto solid substrates, forming LB films. A close packing arrangement of urease was obtained, especially in the mixed LB films, which was inferred with nanogravimetry and electrochemistry measurements. From the blocking effect of the LB films deposited onto indium tin oxide (ITO) substrates, the electrochemical properties of the LB films pointed to a charge transport controlled by the lipid architecture.     

Theoretical study of new LmDHODH and LmTXNPx complexes: structure-based relationships

Structural Chemistry - In this work, a series of eight novel ring-substituted styrylquinolines were synthesized, and in silico physicochemical properties were estimated. The inhibitory activity of...     

Coumarin-Chalcone Hybrids as Inhibitors of MAO-B: Biological Activity and In Silico Studies

Fourteen coumarin-derived compounds modified at the C3 carbon of coumarin with an α,β-unsaturated ketone were synthesized. These compounds may be designated as chalcocoumarins (3-cinnamoyl-2H-chromen-2-ones). Both chalcones and coumarins are recognized scaffolds in medicinal chemistry, showing diverse biological and pharmacological properties among which neuroprotective activities and multiple enzyme inhibition, including mitochondrial enzyme systems, stand out. The evaluation of monoamine oxidase B (MAO-B) inhibitors has aroused considerable interest as therapeutic agents for neurodegenerative diseases such as Parkinson’s. Of the fourteen chalcocumarins evaluated here against MAO-B, ChC4 showed the strongest activity in vitro, with IC₅₀ = 0.76 ± 0.08 µM. Computational docking, molecular dynamics and MM/GBSA studies, confirm that ChC4 binds very stably to the active rMAO-B site, explaining the experimental inhibition data.     

Cold‐drawn induced microstructure in PVC‐bentonite nanocomposites

The mechanical properties and cold drawn‐induced micro and nanostructure of polyvinyl chloride (PVC)‐bentonite nanocomposites have been investigated. Molded sheets with 5 wt% concentration of bentonite and two processing additives were melt extruded and two‐roll‐milled processed. The flame retardant additive promoted polymer intercalation whereas a pigment dispersant promoted clay exfoliation, the polymer matrix showed isotropic orientation. The intercalated nanocomposite exhibited nanoplates oriented with their planes parallel to the molded sheet surface and the Young's modulus and yield stress were significantly enhanced relative to neat PVC. The strain at fracture (～144%) was slightly reduced relative to the matrix (～167%). Cold drawing induced molecular chain orientation along the tensile axis and preserved the orientation of the intercalated nanoclays. The fracture mechanism, as investigated via scanning electron microscopy (SEM) revealed plastic fracture mechanism (similar to neat PVC). On the other hand, the exfoliated nanocomposite did not show any improvement in mechanical properties but rather a significant decay of strain at fracture (～44%). The fractured region, as examined by SEM, exhibited microvoid morphology. Analysis of the fractured region showed PVC macromolecules oriented along the tensile axis but no preferred orientation of the nanoclays. The limited strain at fracture found for this material appears to be associated with the initially randomly oriented nanoclays being unable to orient under the tensile deformation. The nanoclays would act as stress concentrators leading to rapid material's failure due to loss of adhesion with the polymer matrix. The results suggest that exfoliated nanoclays could play a detrimental role when the nanocomposite is subjected to large deformations at temperatures well within the glassy regime. Copyright © 2009 John Wiley & Sons, Ltd.     

Chlorin photosensitizers sterically designed to prevent self-aggregation

The synthesis and photophysical evaluation of new chlorin derivatives are described. The Diels-Alder reaction between protoporphyrin IX dimethyl ester and substituted maleimides furnishes endo-adducts that completely prevent the self-aggregation of the chlorins. Fluorescence, resonant light scattering (RLS) and (1)H NMR experiments, as well as X-ray crystallographic have demonstrated that the configurational arrangement of the synthesized chlorins prevent π-stacking interactions between macrocycles, thus indicating that it is a nonaggregating photosensitizer with high singlet oxygen (Φ(Δ)) and fluorescence (Φ(f)) quantum yields. Our results show that this type of synthetic strategy may provide the lead to a new generation of PDT photosensitizers.     

One-electron oxidation of ferrocenes by short-lived N-oxyl radicals. The role of structural effects on the intrinsic electron transfer reactivities

A kinetic study of the one electron oxidation of substituted ferrocenes (FcX: X = H, COPh, COMe, CO(2)Et, CONH(2), CH(2)OH, Et, and Me(2)) by a series of N-oxyl radicals (succinimide-N-oxyl radical (SINO), maleimide-N-oxyl radical (MINO), 3-quinazolin-4-one-N-oxyl radical (QONO) and 3-benzotriazin-4-one-N-oxyl radical (BONO)), has been carried out in CH(3)CN. N-oxyl radicals were produced by hydrogen abstraction from the corresponding N-hydroxy derivatives by the cumyloxyl radical. With all systems, the rate constants exhibited a satisfactory fit to the Marcus equation allowing us to determine self-exchange reorganization energy values (λ(NO˙/NO(-))) which have been compared with those previously determined for the PINO/PINO(-) and BTNO/BTNO(-) couples. Even small modification of the structure of the N-oxyl radicals lead to significant variation of the λ(NO˙/NO(-)) values. The λ(NO˙/NO(-)) values increase in the order BONO < BTNO < QONO < PINO < SINO < MINO which do not parallel the order of the oxidation potentials. The higher λ(NO˙/NO(-)) values found for the MINO and SINO radicals might be in accordance with a lower degree of spin delocalization in the radicals MINO and SINO and charge delocalization in the anions MINO(-) and SINO(-) due to the absence of an aromatic ring in their structure.     

Design, synthesis and characterisation of guanosine-based amphiphiles

A small library of sugar-modified guanosine derivatives has been prepared, starting from a common intermediate, fully protected on the nucleobase. Insertion of myristoyl chains and of diverse hydrophilic groups, such as an oligoethylene glycol, an amino acid or a disaccharide chain, connected through in vivo reversible ester linkages, or of a charged functional group provided different examples of amphiphilic guanosine analogues, named G1-G7 herein. All of the sugar-modified derivatives were positive in the potassium picrate test, showing an ability to form G-tetrads. CD spectra demonstrated that, as dilute solutions in CHCl(3), distinctive G-quadruplex systems may be formed, with spatial organisations dependent upon the structural modifications. Two compounds, G1 and G2, proved to be good low-molecular-weight organogelators in polar organic solvents, such as methanol, ethanol and acetonitrile. Ion transportation experiments through phospholipid bilayers were carried out to evaluate their ability to mediate H(+) transportation, with G5 showing the highest activity within the investigated series. Moreover, G3 and G5 exhibited a significant cytotoxic profile against human MCF-7 cancer cells in in vitro bioassays.     

Fragmentation of oxime and silyl oxime ether odd‐electron positive ions by the McLafferty rearrangement: new insights on structural factors that promote α,β fragmentation

The McLafferty rearrangement is an extensively studied fragmentation reaction for the odd‐electron positive ions from a diverse range of functional groups and molecules. Here, we present experimental and theoretical results of 12 model compounds that were synthesized and investigated by GC‐TOF MS and density functional theory calculations. These compounds consisted of three main groups: carbonyls, oximes and silyl oxime ethers. In all electron ionization mass spectra, the fragment ions that could be attributed to the occurrence of a McLafferty rearrangement were observed. For t‐butyldimethylsilyl oxime ethers with oxygen in a β‐position, the McLafferty rearrangement was accompanied by loss of the t‐butyl radical. The various mass spectra showed that the McLafferty rearrangement is relatively enhanced compared with other primary fragmentation reactions by the following factors: oxime versus carbonyl, oxygen versus methylene at the β‐position and ketone versus aldehyde. Calculations predict that the stepwise mechanism is favored over the concerted mechanism for all but one compound. For carbonyl compounds, C–C bond breaking was the rate‐determining step. However, for both the oximes and t‐butyldimethylsilyl oxime ethers with oxygen at the β‐position, the hydrogen transfer step was rate limiting, whereas with a CH₂ group at the β‐position, the C–C bond breaking was again rate determining. n‐Propoxy‐acetaldehyde, bearing an oxygen atom at the β‐position, is the only case that was predicted to proceed through a concerted mechanism. The synthesized oximes exist as both the (E)‐ and (Z)‐isomers, and these were separable by GC. In the mass spectra of the two isomers, fragment ions that were generated by the McLafferty rearrangement were observed. Finally, fragment ions corresponding to the McLafferty reverse charge rearrangement were observed for all compounds at varying relative ion intensities compared with the conventional McLafferty rearrangement. Copyright © 2012 John Wiley & Sons, Ltd.