Star‐Shaped Polyaromatic Ethers Coordinated to Redox‐Active Cyclopentadienyliron Moieties

This communication is focused on the controlled design of star‐shaped aromatic ethers with pendent cyclopentadienyliron moieties. A trimetallic core was prepared, which was then reacted with a number of oligomeric ether complexes to give star‐shaped polymers with six, nine, twelve and fifteen pendent cationic cyclopentadienyliron moieties. Cyclic voltammetric studies showed reduction of the iron centers between –0.99 and –1.41 V. Thermogravimetric analysis showed that loss of the metallic moieties occurred between 225 and 284°C.     

Synthesis of substituted norbornenes and their polymerization to polynorbornenes with flexible aliphatic side‐chains

Synthesis and characterization of new thermally stable polynorbornenes functionalized with pendent flexible side‐chains are reported. The flexible side‐chains with terminal hydroxy groups were synthesized via S_NAr reactions of cyclopentadienyliron‐complexed chlorobenzenes with aliphatic diols. Condensation of these side‐chains with exo,endo‐5‐norbornene‐2‐carboxylic acid led to the formation of substituted monomers which were characterized using one‐ and two‐dimensional NMR techniques. Ring‐opening metathesis polymerization of these monomers yielded polynorbornenes with pendent side‐chains.     

Electrochemical investigations of oligomers and polymers containing ruthenium- and iron-arene complexes

Cyclic voltammetry was employed to investigate the electrochemical behavior of numerous cyclopentadienyliron (CpFe⁺) and pentamethyl-cyclopentadienylruthenium (Cp*Ru⁺) coordinated oligomers and polymers. The electrochemical behavior of the iron systems indicated the cyclopentadienyliron complexes had isolated redox centers and that changes in the reversibility of the redox couple occurred with changes in solvent and temperature. In contrast, the monometallic ruthenium systems showed large peak separations that suggested slow kinetics on the CV timescale. The cyclic voltammograms of the larger ruthenium-containing oligomers and polymers showed multiple redox steps indicating complex electrochemical behavior.     

Utilization of solid phase spectrophotometry for the determination of trace amounts of copper using 5-(2-benzothiazolylazo)-8-hydroxyquinoline

A simple, selective, highly sensitive and accurate procedure for the determination of trace amounts of copper has been developed based on solid-phase spectrophotometry. Copper reacts with 5-(2-benzothiazolylazo)-8-hydroxyquinoline (BTAHQ) to give a complex with high molar absorptivity (3.17 × 10⁷ L mol⁻¹ cm⁻¹, 3.07 × 10⁸ L mol⁻¹ cm⁻¹, 1.22 × 10⁹ L mol⁻¹ cm⁻¹, and 1.80 × 10⁹ L mol⁻¹ cm⁻¹), fixed on a Dowex 1-X8 type anion-exchange resin for 10 mL, 100 mL, 500 mL, and 1000 mL, respectively. The absorbance at 667 nm and 800 nm packed in a 1.0 mm cell was measured directly. Calibration is linear over the range 0.2–3.7 μg L⁻¹ with RSD of < 1.28 % (n = 10). The detection and quantification limits of the 500 mL sample method are 79 ng L⁻¹ and 260 ng L⁻¹ when using 60 mg of Dowex 1-X8. For a 1000 mL sample, the detection and quantification limits are 67 ng L⁻¹ and 220 ng L⁻¹ using 60 mg of the exchanger. Increasing the sample volume can enhance the sensitivity. The proposed method was applied to the determination of copper in different environmental water samples (tap, pit, spring, and river), food products (rice, corn flour, and tea), and mushrooms, using the standard addition technique.     

Can be Azo Dyes Obtained by Grinding under Solvent‐Free Conditions?

The solid‐solid reactions of some electron‐donors with sulfanilic acid in the presence of solid sodium nitrite afford azo dyes by self‐catalyzed diazotization of sulfanilic acid (2) under solvent‐free conditions with moderate yields. Also the reactions of some electron‐donors with diazotization of o‐nitroaniline (5), m‐nitroaniline (6) and p‐nitroaniline (7) in the presence of solid sodium nitrite catalyzed by p‐toluenesulfonic acid (PTSA) afford azo dyes under solvent‐free conditions in good yields. This new method totally avoids the use of acids, alkalies, and toxic and/or expensive solvents in diazotization and diazo coupling reactions.     

Reaction of (1,3-dioxo-2,3-dihydro-1H-inden-2-ylidene)propanedinitrile with N-arylisoindolines

In a multistep reaction, 3,3′-(2-aryl-2H-isoindol-1,3-ylene)-di-(1,4-naphthoquinone-2-carbonitriles) 13a-f have been formed in 25-61% yield from a series of N-arylisoindolines 8a-f with (1,3-dioxo-2,3-dihydro-1H-inden-2-ylidene)propanedinitrile (1) in aerated pyridine. The structure of one of these products (13f) has been unambiguously confirmed by a single crystal X-ray structure analysis. Under otherwise the same conditions, 2-(3-methoxyphenyl)-isoindoline (8g) and 1 gave 38% of [4-(2,3-dihydro-1H-isoindol-2-yl)-2-methoxyphenyl]-1,3-dioxoindan-2-ylidene)acetonitrile (15). Rationales for these conversions involving the known rearrangement of the radical anion of 1 into the radical anion of 1,4-naphthoquinone-2,3-dicarbonitrile (3) are presented.     

Polyaniline-coated cerium oxide nanoparticles as an efficient adsorbent for preconcentration of ultra-trace levels of cadmium (ІІ) followed by electrothermal atomic absorption spectrometry

For the first time, polyaniline-coated cerium oxide nanoparticles were synthesized in alkaline media and applied for preconcentration of ultra-trace levels of cadmium (??) in different real samples followed by electrothermal atomic absorption spectrometry. Cerium oxide nanoparticles were synthesized by a microwave method and modified by polyaniline to produce polyaniline-coated cerium oxide nanoparticles. Fourier-transform infrared spectroscopy and scanning electron microscopy were used to characterize the synthesized adsorbent. To optimize the critical experimental conditions; surface response methodology—Box–Behnken experimental design was used. On the basis of the results, pH 8.4, 10?mg of polyaniline-coated cerium oxide nanoparticles, 14.4?min extraction time, and 4.3?min desorption time were selected as the optimum conditions. Under the optimum conditions the calibration curve of cadmium (??) was linear in the range of 0.02–0.4?ng?mL^?1 with a correlation coefficient of 0.9976. The relative standard deviation based on seven replicate analysis of 0.1?ng?mL^?1 cadmium (??) was 4.2% and limit of detection was 0.005?ng?mL^?1 cadmium (??). The analysis of certified reference material shows very good agreement with the certified value. Finally, the proposed method was applied for the determination of ultra-trace levels of cadmium (??) in different water, rice, and tea samples.     

Efficient and Facile Synthesis of Substituted Aminothiadiazolylhydrazonoindolin‐2‐ones

New series of substituted aminothiadiazolylhydrazonoindolin‐2‐ones were prepared in high yields (89–94%) via the cyclocondensation of thiocarbonohydrazides ( 1a , 1b , 1c , 1d ) with 3‐(dicyanomethylene)‐2‐indolone in (ethanol/piperidine) at room temperature. Explanations of these conversations involve the nucleophilic addition on the dicyanomethylene carbon atom. The structures were established by spectroscopic data and single crystal X‐ray crystallography.     

Sandwich Complex‐Containing Macromolecules: Property Tunability Through Versatile Synthesis

Sandwich complexes feature unique properties as the physical and electronic properties of a hydrocarbon ligand or its derivative are integrated into the physical, electronic, magnetic, and optical properties of a metal. Incorporation of these complexes into macromolecules results in intriguing physical, electrical, and optical properties that were hitherto unknown in organic‐based macromolecules. These properties are tunable through well‐designed synthetic strategies. This review surveys many of the synthetic approaches that have resulted in tuning the properties of sandwich complex‐containing macromolecules. While the past two decades have seen an ever‐growing number of research publications in this field, gaps remain to be filled. Thus, we expect this review to stimulate research interest towards bridging these gaps, which include the insolubility of some of these macromolecules as well as expanding the scope of the sandwich complexes.

     

Appraisal of radioactivity and associated radiation hazards in sand samples of four rivers of Punjab province, Pakistan

Natural and anthropogenic radioactivity of sand and water samples collected from the four big rivers of Punjab province, Pakistan, was measured using a high-purity germanium detector coupled with a high resolution multichannel analyser. The average concentration of the naturally occurring radionuclides (226)Ra, (232)Th and (40)K in all the sand samples from the rivers Jhelum, Chenab, Ravi and Indus was found to be 22±0.6, 36±1 and 287±10 Bq kg (-1), respectively, while the concentration of the anthropogenic radionuclide (137)Cs was found to be below the minimum detectable activity, i.e. ~1.2 Bq?kg (-1). All the sand samples have Ra(eq) concentrations lower than the limit of 370 Bq kg (-1). Indoor (H (in)) and outdoor (H (out)) radiation hazard indices were calculated for the samples to assess the radiation hazards arising due to the use of this sand in construction, and were found to be less than unity in the study area. Calculated values of the absorbed dose rate were less than the typical world average value of 59 nGy h (-1), and the annual effective dose rate was also less than the typical world value of 70 μSv, except in the Indus river, in which it is slightly higher then the world average. Results show that the measured values are comparable with other global radioactivity measurements. None of the studied riverbeds was considered a radiological hazard, and their sand can be safely used in construction.