Sulfanilamide-containing coordination compounds of Cu(II) with isatin and N-methylisatin thiosemicarbazones

Isatin (L¹) and N-methylisatin (L²) β-thiosemicarbazones react in ethanol with Cu(II) chloride and bromide in the presence of sulfanilamide (Streptocid, Sf¹), N-acetylsulfanilamide (Sulfacyl, Sf²), Norsulfazole (Sf³), Aethazolum (Sf⁴), and Sulfadimesine (Sf⁵) to form coordination compounds Cu(Sf^1–5)L^1–2X₂ · nH₂O (X = Cl, Br; n = 2–5). All the complexes have a monomeric structure. Thiosemicarbazones L¹ and L² in these complexes are tridentate O,N,S ligands, and sulfanilamides Sf^1–5 are monodentate ligands. Thermolysis of the substances involves the steps of dehydration (70–95°C) and complete decomposition (410–530°C).     

NdFeO3 as a new electrocatalytic material for the electrochemical monitoring of dopamine

A new electrochemical sensor, based on NdFeO₃ nanoparticles as electrocatalytic material, was proposed here for the detection of dopamine (DA). NdFeO₃ nanoparticles were first synthesized by a simple thermal treatment method and subsequent annealing at high temperature (700 °C). The prepared electrocatalytic material has been characterized in detail by SEM-EDX, XRD, and Raman techniques. Characterization results display its sheet-like morphology, constituted by a porous network of very small orthorhombic NdFeO₃ nanoparticles. NdFeO₃ electrocatalytic material was then used to modify the working electrode of screen-printed carbon electrodes (SPCEs). Electrochemical tests demonstrated that NdFeO₃– modified screen-printed carbon electrode (NdFeO₃/SPCE) exhibited a remarkable enhancement of the dopamine electrooxidation, compared to the bare SPCE one. The analytical performance of the developed sensor has been evaluated for the detection of this analyte by means of the square-wave voltammetry (SWV) technique. The modified electrode showed two linear concentration ranges, from 0.5 to 100 μM and 150 to 400 μM, respectively, a limit of detection (LOD) of 0.27 μM (at S/N = 3), and good reproducibility, stability, and selectivity. Additionally, we also report an attempt made to propose the modified sensor for the simultaneous detection of dopamine and uric acid (UA). The procedure was also applied for the determination of dopamine in spiked real samples. So, this paper reports for the first time the use of a modified NdFeO₃ screen-printed electrode for developing an electrochemical sensor for the quantification of important biomolecules.

Graphical abstract

     

Chemiluminescent determination of reactive hydrocarbons

Summary Chemiluminescent reactions of ozone with several classes of compounds at different temperatures are described. In a reaction chamber in front of a photomultiplier ozone is mixed with the compounds studied such as alkanes, olefins, alcohols, aromatics, C₂H₂, NO, vinyl chloride or H₂S. The chemiluminescent emission is proportional to the concentration of the compound involved. At room temperature only olefinic hydrocarbons respond but at temperatures above 150°C also a response for alkanes, alcohols, CO etc. is obtained. It is suggested that next to the ozonide-excited formaldehyde mechanism the CO-CO ₂ ^* mechanism is responsible for the chemiluminescent emission at high temperature. A detection limit of a few ppb is achieved. Possible applications are a selective gas-chromatographic detector, an air pollution monitor for instance for CO, and a photochemical reactivity monitor.

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Bestimmung reaktiver Kohlenwasserstoffe durch Chemiluminescenz

Zusammenfassung Chemiluminescenzreaktionen von Ozon mit verschiedenen Verbindungsgruppen (hauptsächlich Kohlenwasserstoffe) bei unterschiedlichen Temperaturen werden beschrieben. In einer Reaktionskammer werden die Verbindungen vor einem Photomultiplier mit Ozon vermischt. Es handelt sich u. a. um folgende Verbindungstypen: Alkane, Olefine, Alkohole, Aromaten, C₂H₂, NO, Vinylchlorid, H₂S. Die Emissionsintensität ist proportional der Konzentration. Bei Raumtemperatur sprechen nur Olefine an, die übrigen Verbindungen erst über 150°C. Die Emission bei höherer Temperatur wird neben der Bildung von Formaldehyd auf die Reaktion CO-CO ₂ ^* zurückgeführt. Die Nachweisgrenze beträgt wenige ppb. Als mögliche Anwendungsgebiete werden ein selektiver GC-Detektor, ein Monitor für Luftverunreinigungen (z.B. für CO) sowie ein Monitor zur Messung photochemischer Reaktivität der Luft genannt.

Presented at the 6th Annual Symposium on Recent Advances in the Analytical Chemistry of Pollutants, April 21–23, 1976; Vienna, Austria.     

Relationship between the longitudinal relaxation rates of water protons and of well defined paramagnetic centers at low temperature in hydrated vermiculite

A good agreement has been observed between the proton longitudinal relaxation rate in the two and one layer hydrate of the Na-Llano vermiculite, the location of the Fe³⁺ paramagnetic centers within the octahedral and tetrahedral layers of the lattice and the electronic longitudinal relaxation rate using the dipolar electronic—proton spin interaction. The water content influences noticeably the electronic longitudinal relaxation time.     

Investigation of the electronic structure of the TCNQ-TTF system. I. TCNQ and TTF monomers and dimers in the all-valence-electron approximation

Closed-shell and DODS CNDO/2 calculations have been performed for neutral and charged TCNQ and TTF monomers and different dimers. For the sake of comparison the calculation have also performed for the corresponding TCNE molecules.The most important result obtained indicates a large splitting of the lowest unfilled level of TCNQ in going from the monomer to the stacked (TCNQ)₂ dimer. The same holds true for the HOMO level of the (TTF)₂ dimer. This indicates that one should expect a broad conduction band for the neutral poly (TCNQ) chain and a broad valence band for the neutral poly (TTF) chain. In order to test the quality of the CNDO/2 approximation scheme a comparison is attempted with existing experimental findings as well as with some MINDO results and available theoretical predictions within different approximation schemes.     

Spectres de Masse de Derives de l'Atractyloside. Determination du Nombre de Substituants par Combinaison d'Acetylation et de Silylation

Different transformations of the functions fixed on a heterocyclic molecule were made. It is thus possible to quickly determine the number of functions of each type present in the molecule: e.g. (i) all the functions are silylated and (ii) the alcohols are acetylated whilst the sulfates and acids are silylated. Mass spectra of atractylate, apoatractylate and gummiferine have been studied and the substituents are counted and enumerated.     

Zur Magnetochemie des zweiwertigen Silbers Neue Fluoroargentate(II): Cs2AgF4, Rb2AgF4 und K2AgF4

Magnetochemistry of Divalent Silver. New Fluoroargentates(II): Cs₂AgF₄, Rb₂AgF₄, and K₂AgF₄ Hitherto unknown blue compounds Rb₂AgF₄ and Cs₂AgF₄ are prepared. Guinier patterns show, that Cs₂AgF₄ cristallise in the K₂NiF₄ structure (a = 4.58₁, c = 14.19₂ Å). The structure of the Rb-compound is still unknown. The magnetic behaviour of K₂AgF₄, Rb₂AgF₄, and Cs₂AgF₄ is discussed.     

Mittlere Schwingungsamplituden einiger linearerXY 2-Interhalogenanionen

The mean amplitudes of vibration of ICl₂ ^–, IBr₂ ^–, BrCl₂ ^– and ClF₂ ^– have been calculated, from known spectroscopic data, in the temperature range between O° and 1000°K. Also generalized mean-square amplitudes and values for theBastiansen—Morino shrinkage effect are reported. The results are briefly discussed.

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Mit 1 Abbildung     

Nouvelle méthode de dosage automatique de substances oxydantes ou réductrices par potentiométrie différentielle : Partie I. Étude théorique

A new method is proposed for routine determinations of oxidizable and reducible substances. A mathematical development and criticism of the method of Schierjott has led to a fundamental modification of the earlier experimental conditions (ratio of the oxidized/reduced forms of the reagent at the start and end of the redox reaction). This improvement allows a considerable increase in the sensitivity of the method and is particularly advantageous for the determination of substances of low reactivity, e.g. carbohydrates. Other advantages are a reduction in the quantity and thus cost of the necessary reagent, and a decreased risk of precipitation of the substances involved. The mathematical treatment of the proposed version allows a rigorous theoretical comparison of the two methods. An evaluation of the quality of the approximations introduced into both methods is also proposed, based on the calculation of the deviation (absolute and relative differences) of approximated values from theoretical values. The final part of the work deals with optimization of the different principal parameters, i.e. concentration of the reagent, temperature and reaction time.     

Variable electronegativity SCF-MO calculations on the electronic structure and spectra of some substituted benzenes I. Monosubstitutions

π-electron SCF-MO theory in its variable electronegativity formalism has been applied to some monosubstituted benzenes. Calculated charge densities and bond orders for the ground and the first excited electronic states are correlated with chemical reactivity and the changes in molecular geometry on electronic excitation. The calculated results for spectra are compared with those obtained using the PPP method and also with the available experimental data.