The effect of the number of carbohydrate moieties on the azaphthalocyanine properties

A series of azaphthalocyanines (AzaPc) bearing one, two, four or eight isopropylidene-protected galactosyl units was prepared by azide-alkyne click reaction or by classical Pc template cyclotetramerization of the corresponding dicyanopyrazine and AzaPc properties important for photodynamic therapy were compared. All compounds absorbed at long wavelengths (above 650 nm) and belonged to strong singlet oxygen producers (Φ(Δ) = 0.58-0.64) retaining significant fluorescence emission (Φ(F) = 0.026-0.23). The only exception was the compound with four isopropyliden-protected galactosyl units where partial aggregation was observed. Removal of protecting groups increased the polar character of all AzaPc. However, only AzaPc bearing eight galactoses was found to be water-soluble (105 mg mL(-1)) but noticeably aggregated in water as well as in organic solvents (DMF, DMSO). Amphiphilic AzaPc bearing one deprotected galactose was incorporated into the lipidic bilayer of liposomes in a nonaggregated form. Liposomes may therefore be a suitable delivery system for this amphiphilic photosensitizer.     

Characterization of perchlorate in a new frozen human urine standard reference material

Perchlorate, an inorganic anion, has recently been recognized as an environmental contaminant by the US Environmental Protection Agency. Urine is the preferred matrix for assessment of human exposure to perchlorate. Although the measurement technique for perchlorate in urine was developed in 2005, the calibration and quality assurance aspects of the metrology infrastructure for perchlorate are still lacking in that there is no certified reference material (CRM) traceable to the International System of Units. To meet the quality assurance needs in biomonitoring measurements of perchlorate and the related anions that affect thyroid health, the National Institute of Standards and Technology (NIST), in collaboration with the Centers for Disease Control and Prevention (CDC), developed Standard Reference Material (SRM) 3668 Mercury, Perchlorate, and Iodide in Frozen Human Urine. SRM 3668 consists of perchlorate, nitrate, thiocyanate, iodine, and mercury in urine at two levels that represent the 50th and 95th percentiles, respectively, of the concentrations (with some adjustments) in the US population. It is the first CRM being certified for perchlorate. Measurements leading to the certification of perchlorate were made collaboratively at NIST and CDC using three methods based on liquid or ion chromatography tandem mass spectrometry. Potential sources of bias were analyzed, and results were compared for the three methods. Perchlorate in SRM 3668 Level I urine was certified to be 2.70?±?0.21?μg?L(-1), and for SRM 3668 Level II urine, the certified value is 13.47?±?0.96?μg?L(-1).     

A note on a family of two-variable polynomials

The main object of this paper is to construct a two-variable analogue of Jacobi polynomials and to give some properties of these polynomials. We show that these polynomials are orthogonal, then we obtain various recurrence formulas for them. Furthermore, we give some integral representations for these polynomials.     

Cyclic voltammetry and viscosity measurements of aggregated assemblies of anionic surfactants with nonionic surfactants and triblock copolymers

Cyclic voltammetry (CV) and viscosity measurements have been employed to study the aggregation behavior of mixed micellar systems of anionic surfactant (dioctyl sulfosuccinate sodium salt, AOT) with conventional nonionic surfactants such as Brij 35/TritonX-100/Tween 20/Tween 80/Myrj 45 and two triblock copolymers (L64 and F68). Critical micelle concentration (cmc) values have been determined for various micellar systems from CV measurements using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as an electroactive probe at 25 °C. Diffusion coefficient (D) has been evaluated from Randles–Sevcik equation which showed an overall decrease for most of the binary systems. The negative values of interaction parameters (β) obtained from regular solution theory suggest the synergistic behavior in all the binary systems except AOT + Tween 80 mixtures. The mixed systems of AOT with triblock copolymers showed stronger synergistic interactions than that of mixed systems of AOT with nonionic surfactants. A comparative evaluation of mixed systems of anionic surfactants AOT and sodium dodecyl sulfate with Myrj 45 and AOT + L64 and F68 has been made on the basis of different micellar parameters and structural properties of surfactants. Viscosity measurements also show similar type of interactions in the mixed micelles.     

Synthesis and physico-chemical properties of some Ni(II) complexes with isatin-hydrazones

New Ni(II) complexes with bioactive bishydrazones ligands based on (pyridine-2-carboxaldhyde)-3-isatin, (2-acetylpyridine)-3-isatin, and (2-benzoylpyridine)-3-isatin have been synthesized and characterized by elemental analysis, conductivity measurements, IR and UV-Vis spectroscopy, and thermal analysis. The complexes stoichiometry and formation constants have been determined. The results suggest that isatinbishydrazones act as neutral tridentate ligands with ONN sites coordinating to the metal ion via isatin C=O, azomethine CR=N, and pyridine C=N groups to give [Ni(L)H₂O]Cl₂·2H₂O, (L = neutral tridentate isatin hydrazone ligand). Kinetics and thermodynamic parameters of the complexes thermal decomposition have been elucidated from the thermal data using Coats and Redfern method, which has confirmed the first order kinetics.     

Recent trends in the synthesis of 1,2,3-thiadiazoles

Abstract

1,2,3-Thiadiazoles, structurally active pharmacophores have attracted significant attention of synthetic chemists, medicinal and pharmaceutical researchers because of their versatile biological activities against various diseases such as herbicidal, insecticidal, antiviral, antitumor, antimicrobial, anticancer, plants activator and anti-amoebic activities. A literature survey of the last decade presented in this review article summarizes the major synthetic approaches, methodologies and strategies adopted for the synthesis of 1,2,3-thiadiazole scaffolds which will be help for medicinal chemists and pharmacists in future synthesis and development of novel therapeutic agents.     

Retracted: Acid‐Catalyzed Aquation of Ni(II)‐Hydrazone Complexes: Kinetics and Solvent Effect

Complexes of the type [Ni(L)(H₂O)]Cl₂·nH₂O, where L = 2‐pyridyl‐3‐isatinbishydrazone ligands, have been synthesized and characterized on the bases of elemental analysis, molar conductance, IR, electronic spectra, and thermal analysis (TGA and DTA). Acid‐catalyzed aquation of the Ni(II) isatin‐bishydrazone complexes was followed spectrophotometrically in various water–methanol and water–acetone mixtures at temperature 298 K. Kinetic behavior of the acid aquation is a linear rate law, indicating that the acid‐catalyzed aquation of these complexes in water–methanol and water–acetone mixtures follows a rate law with k_obs = k₂[H⁺]. The effect of the mole fraction of the ganic solvent, i.e., methanol and acetone, on the acid aquation has been analyzed; the decrease in the rate constant values with increasing of the methanol or acetone ratios is attributable to the effect of the co‐organic solvent on the initial states of the acid aquation by the destabilization of the H⁺ ion.     

Development of frozen whale blubber and liver reference materials for the measurement of organic and inorganic contaminants

Summary Fresh frozen homogenates of pilot whale blubber and liver tissue were prepared for use as control materials for the determination of organic and inorganic contaminants in marine mammal tissue analyses. The blubber material was analyzed to determine 30 polychlorinated biphenyl congeners and 16 chlorinated pesticides using gas chromatography with electron capture detection and gas chromatographymass spectrometry. A total of 39 trace elements and methylmercury were determined in the liver homogenate using instrumental neutron activation analysis, voltammetry, and cold vapor atomic absorption spectroscopy. The preparation and analysis of these two tissue materials are part of the development of marine mammal tissue reference materials.