Synthesis and characterization of new mesogenic esters derived from 1,2,4-oxadiazole and study the effect of alkoxy chain length in their liquid crystalline properties

In this study, a new series of non-symmetrically 3,5-disubstituted of 1,2,4-oxadiazole derivatives, 4-[5-(4-methylphenyl)-1,2,4-oxadiazol-3-yl]-phenyl-4-alkoxybenzoate (G₁–G₁₁), which containing ether and ester linkages in the same molecule, is synthesized using different synthetic procedures and their structures are confirmed by several spectroscopic techniques (FT-IR and ¹H nuclear magnetic resonance). The mesomorphic properties of these compounds are studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM); all these derivatives exhibited as mesogens and displayed an enantiotropic liquid crystal with nematic texture, the nematogenic phase of these materials was appeared in wide temperature ranges on heating and cooling cycles that were observed by POM and DSC. The influence of 1,2,4-oxadiazole ring and the elongation of alkyl chain in the mesomorphic properties of this series were investigated. The mesogenic behaviour of this series was compared with the compounds possessing a somewhat similar structure.     

Recoverable salen-based macrocyclic chiral complexes; catalysts for enantioselective Henry reactions

Cobalt and chromium complexes have been prepared from chiral calix–salen cyclic ligands. The corresponding tetrahydrosalen reduced forms have been used for copper salt complexation. These new chiral catalysts have been tested for their ability to promote asymmetric Henry reactions between various aldehydes and nitromethane under heterogeneous conditions. The best results were obtained by using tetrahydrosalen-based copper macrocycles, in terms of activity, selectivity, and stability during the recycling process. Ten consecutive runs could indeed be performed with the same catalyst batch to produce the target 1-(2-methoxy-phenyl)-2-nitro-ethanol with highly stable values in terms of yield and enantioselectivity (up to 94% ee).     

High-efficiency pyrene-based blue light emitting diodes: aggregation suppression using a calixarene 3D-scaffold

An efficient blue light emitting diode based on solution processable pyrene-1,3-alt-calix[4]arene is demonstrated, providing a record current efficiency of 10.5 cd A(-1) in a simple non-doped OLED configuration. Complete suppression of pyrene aggregation in the solid state is achieved by controlling chromophore dispersion using the 1,3-alt-calix[4]arene scaffold.     

In Situ Synthesis of Self‐Assembled Gold Nanoparticles on Glass or Silicon Substrates through Reactive Inkjet Printing

A facile and low cost method for the synthesis of self‐assembled nanoparticles (NPs) with minimal size variation and chemical waste by using reactive inkjet printing was developed. Gold NPs with diameters as small as (8±2) nm can be made at low temperature (120 °C). The size of the resulting NPs can be readily controlled through the concentration of the gold precursor and oleylamine ink. The pure gold composition of the synthesized NPs was confirmed by energy‐dispersive X‐ray spectroscopy (EDXS) analysis. High‐resolution SEM (HRSEM) and TEM (HRTEM), and X‐ray diffraction revealed their size and face‐centered cubic (fcc) crystal structure, respectively. Owing to the high density of the NP film, UV/Vis spectroscopy showed a red shift in the intrinsic plasmonic resonance peak. We envision the extension of this approach to the synthesis of other nanomaterials and the production of tailored functional nanomaterials and devices.     

Anti-Microbial,Anti-Oxidant,and α-Amylase Inhibitory Activity of Traditionally-Used Medicinal Herbs: A Comparative Analyses of Pharmacology,and Phytoconstituents of Regional Halophytic Plants’ Diaspora

Halophytes are the category of plants growing under harsh conditions of super-salinity, and are wide-spread in the coastal Mediterranean climatic conditions and desert oasis. They are adept at surviving through maintaining excessive production of enzymatic, and non-enzymatic secondary metabolites, especially phenolics and flavonoids that primarily work as anti-oxidants and phytoalexins. Five major halophyte species growing in the kingdom’s Qassim’s high-salted desert regions were investigated for confirming their traditionally used biological activity of sugar-control and anti-infectious properties. In this context, the comparative presence of phenolics, and flavonoids together with anti-microbial, anti-oxidants, and the anti-diabetic potentials of the plants’ extracts were investigated through the α-amylase inhibition method. The highest concentrations of phenolics and flavonoids were detected in Salsola imbricata (360 mg/g of the extract as Gallic-Acid-Equivalents/GAE, and 70.5 mg/g of the extract as Rutin-Equivalents/RE). In contrast, the lowest concentrations of phenolics and flavonoids were detected in Salsola cyclophylla (126.6 mg/g GAE, and 20.5 mg/g RE). The halophytes were found rich in trace elements, a factor for water-retention in high-salinity plants, wherein iron and zinc elements were found comparatively in higher concentrations in Aeluropus lagopoides (4113 µg/kg, and 40.1 µg/kg, respectively), while the copper was detected in higher concentration (11.1 µg/kg) in S. imbricata, analyzed through Inductively Coupled Plasma Optical Emission Spectrometric (ICP-OES) analysis. The anti-oxidant potentials and α-amylase enzyme inhibition-based anti-diabetic activity of S. imbricata was significantly higher than the other halophytes under study, wherein S. cyclophylla exhibited the lowest level of α-amylase inhibition. The maximum DPPH radicals’ (52.47 mg/mL), and α-amylase inhibitions (IC₅₀ 22.98 µg/mL) were detected in A. lagopoides. The anti-microbial activity against the Methicillin-Resistant Staphylococcus aureus was strongly exhibited by Zygophyllum simplex (33 mm Inhibition Zone-Diameter, 50 µg/mL Minimum-Inhibitory-Concentration), while Escherichia coli, Enterococcus faecalis, and Candida albicans growths were moderately inhibited by Tamarix aphylla. The current findings exhibited significant differences among the locally distributed halophytic plants species with regards to their bioactivity levels, anti-oxidant potentials, and the presence of trace elements. The ongoing data corroborated the plants’ traditional uses in infections and diabetic conditions. The enhanced local distribution of the plants’ diaspora and higher density of occurrence of these plants species in this region, in comparison to their normal climatic condition’s counterparts, seemed to be affected by humans’ use of the species as part of the traditional and alternative medicine over a period of long time.     

Synthesis and characterisation of mesoporous hybrid silica-polyoxometalate aerogels for photocatalytic degradation of rhodamine B and methylene blue

ABSTRACT

Mesoporous silica aerogel/polyoxometalate hybrids were successfully synthesised under mild conditions, and were investigated towards photocatalytic degradation of Rhodamine B and Methylene Blue dye models in aqueous media under ultraviolet irradiation. The materials were characterised, in the solid state, by various tools such as FTIR, TGA, and powder XRD, in order to gather information about their chemical and structural properties. Moreover, UV-Vis, AAS, BET, SEM, and EDX techniques were used to confirm the polyoxometalates’ loading and their distribution onto the silica aerogels’ surface. The most important analytical technique was the Nitrogen adsorption-desorption, which revealed a significant increase in the specific surface area and pore volume of the hybrid catalysts after immobilisation. The synthesised hybrid catalysts, TEOS/PW₁₂ and TEOS/SiW₁₂, have shown efficient photocatalytic activity towards Methylene Blue and Rhodamine B degradation within 120 min under ultraviolet illumination, thus reaching a degradation percentage of 81–98% and 55–90%, respectively. UV-Vis analysis was employed to scrutinise the formation of intermediate species and revealed that the photocatalytic degradation process proceeded to completion within a surprisingly short time of ~5 min.     

Antihyperlipidemic properties of novel N-(benzoylphenyl)-5-substituted-1H-indole-2-carboxamides in Triton WR-1339-induced hyperlipidemic rats

In the search for new potential antihyperlipidemic agents, the present study focuses on the synthesis of novel N-(benzoylphenyl)-5-substituted-1H-indole-2-carboxamides (compounds 8-12, 15, 16, 18) and investigating their antihyperlipidemic activity using Triton WR-1339-induced hyperlipidemic rats as an experimental model. Hyperlipidemia was developed by intraperitoneal injection of Triton WR-1339 (250 mg/kg body weight). The tested animals were divided into normal control (NCG), hyperlipidemic (HG), compound 8, 9, 15, 16, 18- and bezafibrate treated groups. At a dose of 15 mg/kg body weight, compounds 9, 16, 18 and bezafibrate (100 mg/kg) significantly (p < 0.0001) reduced elevated plasma triglycerides levels after 12 h compared to the hyperlipidemic control group. However, only the group treated with compounds 9, 16 and 18 showed an obviously significant (p < 0.001) reduction in plasma total cholesterol levels after 12 h compared to the hyperlipidemic control group. Moreover, high density lipoprotein-cholesterol levels were significantly (p < 0.0001) increased in all treated groups after 12 h compared to the hyperlipidemic control group, except for compounds 8 and 15 which revealed inactive. It is therefore reasonable to assume that compounds 9, 16 and 18 may have potential in the treatment of hyperlipidemia.     

Prediction of flow stress and textures of AZ31 magnesium alloy at elevated temperature

The viscoplastic behaviour of magnesium alloys at high temperatures leads to highly temperature-dependent mechanical properties. While at high strain rates a notable strain hardening response is observed, at low strain rates the material shows a smooth plastic response with negligible amount of hardening. This complicated behaviour is due to different deformation mechanisms that are active at different strain rate regimes, resulting in different strain rate sensitivity parameters. In this study we show, by utilizing both numerical simulations and experiments, that this behaviour can be predicted by a model that combines two deformation mechanisms, grain boundary sliding mechanism and dislocation glide mechanism. We discuss the importance of each deformation mechanism at different strain rate regimes based on the findings of modelling and experimental results for AZ3 magnesium alloy. By developing a model that includes the above-mentioned two deformation mechanism, the prediction of flow properties is expanded to a wide range of strain rate regimes compared to previous study. The obtained numerical findings for the stress–strain behaviour as well as texture evolution show good agreement with the experimental results.