Cyclooctenyl complexes of palladium(II) with multidentate N-heterocycles

[Pd(cod)(cotl)]ClO₄ (cod = 1,5-cyclooctadiene, cotl = cyclooctenyl, C₈H₁₃ ^–) undergoes substitutions with multidentate N-heterocycles: 1,3-bis(benzimidazolyl)benzene (L¹), 1,3-bis(1-methylbenzimidazol-2-yl)benzene (L²), 2,6-bis(benzimidazolyl)pyridine (L³) and 2,6-bis(1-methylbenzimidazol-2-yl)pyridine (L⁴) to yield mono/binuclear complexes: [Pd(cotl)(L¹)(OClO₃)], [Pd(cotl)(L)]ClO₄ (L = L² or L³) and [Pd(cotl)₂(L⁴)](ClO₄)₂. Dihalobridged binuclear complexes [PdX(cotl)]₂ (X = Cl or Br) undergo halogen bridge cleavages with the multidentate N-heterocycles to form binuclear complexes of the type [PdX(cotl)₂L] (X = Cl or Br; L = L¹, L², L³ or L⁴). The complexes were characterized by elemental analyses, ¹H-, ¹³C-n.m.r., i.r., far-i.r. and FAB-mass spectral studies.     

Prochlorperazine bismethanesulfonate: Sensitive and selective reagent for the spectrophotometric determination of microgram amounts of osmium

Prochlorperazine bismethanesulfonate (PCPMS) is proposed as a new sensitive and selective reagent for the spectrophotometric determination of microgram amounts of osmium. PCPMS forms a red-colored species with osmium(VIII) or osmium(VI) instantaneously at room temperature in 5 M phosphoric acid medium. The red species exhibits maximum absorbance at 529 nm. Beer's law is valid over the concentration range 0.05–3.6 ppm for osmium(VIII) and 0.15–6.4 ppm for osmium(VI). Sandell's sensitivity of the reaction is 2.89 nm cm^?2 for osmium(VIII) and 4.24 ng cm^?2 for osmium(VI). The effects of time, temperature, acidity, order of addition of reagents, reagent concentration, and diverse ions are investigated. The application of the proposed method in the determination of osmium content in synthetic ores has been explored.     

High-Performance Liquid Chromatographic Method for the Determination of Nimesulide in Pharmaceutical Preparations

A simple, rapid, and precise high-performance liquid chromatographic method for the determination of nimesulide in pharmaceutical preparations was proposed using Ibuprofen as an internal standard. The separation was performed on a CLC C₁₈ (5 m, 25 cm × 4.6 mm i.d.) column with a mobile phase consisting of an acetonitrile–0.05 M KH₂PO₄ buffer mixture of pH 7.00 (55 : 45, v/v). The detection was carried out at 230 nm and the linearity range was found to be 0.5–100 g/mL. The method has been applied successfully to the determination of nimesulide in pharmaceutical formulations. The recovery values were found to be in the range of 99.23–100.13% with RSD values of less than 0.97%.     

Spectrophotometric determination of microamounts of gold(III) with propericiazine

Propericiazine is proposed as a new reagent for the spectrophotometric determination of gold(III). The reagent forms an orange-red-colored species with gold(III) instantaneously in 4–8 M phosphoric acid. The orange-red species exhibits maximum absorbance at 511 nm. Beer's law is valid over the concentration range 0.1–7.0 μg/ml. The molar absorptivity is found to be 3.85 × 10⁴ liter mol⁻¹ cm⁻¹. The effects of acidity, time, order of addition of reagents, temperature, reagent concentration, and diverse ions are investigated.     

Cationic carbonyl complexes of ruthenium(II) and osmium(II) containing 2,2′-bipyridyl and 1,10-phenanthroline

Summary Reactions of ruthenium carbonyl complexes of the type [RuX₂(CO)(Ph₂RAs)₃] (X=Cl or Br; R=Me or Et) with 2,2-bipyridyl (bipy) and 1,10-phenanthroline (phen) in alcohol produce orange red cationic products of the formula [RuX(CO)(N-N)(Ph₂RAs)₂]ClO₄ (N-N=bipy or phen). Likewise, the hydridocarbonyls of ruthenium and osmium of the type [MHX(CO)(Ph₂RAs)₃] (M=Ru or Os) react with bipy and phen to yield yellow cationic complexes of the composition [(MH(CO)(N-N)(Ph₂RAs)₂]ClO₄. Structures have been assigned to all the complexes on the basis of i.r. and¹ H n.m.r. spectral data.     

Spectrophotometric studies on platinum—Promethazine hydrochloride complex

Promethazine hydrochloride forms a yellowish-green complex with platinum(IV) in sodium acetate-hydrochloric acid buffer containing copper catalyst. The complex has an absorption maximum at 406 nm with molar absorptivity 1.001 × 10⁴ liters mol^?1 cm^?1. The sensitivity of the reaction is 19.5 ng/cm² for $\text{log}\text{I °}\text{I}\text{= 0.001}$. Beer's law is valid over the range 0.5–7.5 ppm of platinum(IV) with optimum concentration range 0.8-7.3 ppm. Continuous variations, mole ratio, and slope ratio methods indicate 1:1 composition for the complex. The effects of pH, time, temperature, order of addition of reagents, reagent concentration, and interferences from various ions are reported.     

Assay of sulphur compounds with 1-chlorobenzotriazole

A simple but accurate potentiometric method for the estimation of certain sulphur containing organic compounds has been developed, based on their oxidation with 1-chlorobenzotriazole. A back-titration procedure can also be used. The nature of oxidation in different media is discussed and the oxidation products have been identified.     

Dual Recycling of Depolymerization Catalyst and Biodegradable Polyester that Markedly Outperforms Polyolefins

Chemically recyclable, circular polymers continue to attract increasing attention, but rendering both catalysts for depolymerization and high-performance polymers recyclable is a more sustainable yet challenging goal. Here we introduce a dual catalyst/polymer recycling system in that recyclable inorganic phosphomolybdic acid catalyzes selective depolymerization of high-ceiling-temperature biodegradable poly(δ-valerolactone) in bulk phase, which, upon reaching suitable molecular weight, exhibits outstanding mechanical performance with a high tensile strength of ≈66.6 MPa, fracture strain of ≈904 %, and toughness of ≈308 MJ m⁻³, and thus markedly outperforms commodity polyolefins, recovering its monomer in pure state and quantitative yield at only 100 °C. In sharp contrast, the uncatalyzed depolymerization not only requires a high temperature of >310 °C but is also low yielding and non-selective. Importantly, the recovered monomer can be repolymerized as is to reproduce the same polymer, thereby closing the circular loop, and the recycled catalyst can be reused repeatedly for depolymerization runs without loss of its catalytic activity and efficiency.     

Simultaneous Determination of Tamsulosin and Dutasteride in Human Plasma by LC–MS–MS

A sensitive and selective liquid chromatographic tandem mass spectrometric (LC–MS–MS) method was developed for simultaneous identification and quantification of tamsulosin and dutasteride in human plasma, which was well applied to clinical study. The method was based on liquid–liquid extraction, followed by an LC procedure with a Gemini C-18, 50 mm × 2.0 mm (3 μm) column and using methanol:ammonium formate (97:3, v/v) as the mobile phase. Protonated ions formed by a turbo ionspray in positive mode were used to detect analytes and internal standard. MS–MS detection was by monitoring the fragmentation of 409.1 → 228.1 (m/z) for tamsulosin, 529.3 → 461.3 (m/z) for dutasteride and 373.2 → 305.3 (m/z) for finasteride (IS) on a triple quadrupole mass spectrometer. The lower limit of quantification for both tamsulosin and dutasteride was 1 ng mL^?1. The proposed method enables the unambiguous identification and quantification of tamsulosin and dutasteride for clinical drug monitoring.     

A strategy for ready preparation of glycolipids for multivalent presentation

The olefinic residue of n-pentenyl glycosides serves as the trigger for regioselective construction of higher saccharides and then for elaboration in multivalent glycolipids. [reaction: see text]