Silver-catalyzed cycloisomerization of 1,n-allenynamides

A variety of allenynamides can undergo cycloisomerization reactions in the presence of silver triflate thus leading to the formation of N-containing heterocycles incorporating cross-conjugated trienes. Access to new dienic 4-piperidinone and azepane motifs was achieved. An extension to one-pot tandem sequences involving silver-catalyzed cycloisomerization/Diels-Alder reaction was also examined.     

Spectral phase effects on nonlinear resonant photochemistry of 1,3-cyclohexadiene in solution

We have investigated the ring opening of 1,3-cyclohexadiene to form 1,3,5-cis-hexatriene (Z-HT) using optical pulse shaping to enhance multiphoton excitation. A closed-loop learning algorithm was used to search for an optimal spectral phase function, with the effectiveness or fitness of each optical pulse assessed using the UV absorption spectrum. The learning algorithm was able to identify pulses that increased the formation of Z-HT by as much as a factor of 2 and to identify pulse shapes that decreased solvent fragmentation while leaving the formation of Z-HT essentially unaffected. The highest yields of Z-HT did not occur for the highest peak intensity laser pulses. Rather, negative quadratic phase was identified as an important control parameter in the formation of Z-HT.     

Determination of Aromatic Arsines in Environmental Solids by Direct Thermal Desorption Gas Chromatography

To quantify aromatic arsines in the environment, such as World War I era chemical warfare agents and degradation products of arsenicals used in agriculture, a sensitive, selective, and direct method is needed. We describe the development and optimization of a method for the measurement of trace levels of triphenylarsine used as a model aromatic arsenic compound. Triphenylarsine was determined at low µg/g levels in sand, soil, and lake sediment by thermal desorption before gas–liquid chromatography (GC) with mass spectrometric and pulsed flame photometric detection. The dithiol derivative of phenylarsonic acid was used as an internal standard, thereby significantly improving the precision of the method. The desorption conditions were studied and found to be optimal at 350°C for 15?min. Significant improvement in precision was realized by preparing the solid samples as slurries in acetone and by inserting a small (～100?mg) quartz wool plug into the sample vial. The method was applied to determine triphenylarsine in authentic soil and sediment samples that had been fortified with triphenylarsine and aged for at least 15 days. Recoveries for soil samples ranged from 84.3?±?2.3 to 87.7?±?1.3%, while lower recoveries were obtained for sediment samples (75.1?±?3.0%). The detection limit for triphenylarsine in soil was 3.14?ng with a precision of 7.10% (n?=?4). Using these optimized conditions, the performance of the direct thermal desorption GC method for sample introduction was greatly improved compared to methods that have been reported in the literature.     

Ultraviolet radiation exposure of children and adolescents in Durban,South Africa

The solar ultraviolet radiation (UVR) exposure of 30 children and adolescents in three age groups (4-6 years, 7-9 years and 13-14 years) was measured for 1 week in late summer (February-March) in Durban, South Africa, using UVR-sensitive polysulfone film badges (PSFB) attached to the lapel region of the body. The mean and median values for all ages over the study period were 2.0 and 1.2 standard erythemal dose (SED) units, respectively, where 1 SED = 100 J x m(-2). Individual PSFB doses were analyzed as a function of age, gender and behavior. No significant statistical differences were found between different age groups; however, there was a statistical difference between males and females, with males generally receiving higher PSFB doses. Subjects completed UVR exposure journals documenting their time outdoors, shade versus sun conditions, nature of their activities, clothing worn and their use of sunscreen for each day of the study. Activity patterns were noted as the most important factor influencing individual UVR dose. Ambient erythemal UVR was measured by a Yankee Environmental Systems UVB pyranometer, and a relationship between ambient UVR and individual UVR dose was derived. On average, subjects received a dose of 4.6% of the total daily erythemal UVR. Based on this factor, the potential dose of an individual over a full annual cycle was estimated. Accordingly, there were 139 days during the year when an individual with skin type I (light skin) would be likely to experience minimal erythema and 97 and 32 days for individuals with skin types II and III, respectively.     

Phase control of the competition between electronic transitions in a solvated laser dye

Excited state population can be manipulated by resonant chirped laser pulses through pump–dump processes. We investigate these processes in the laser dye LD690 as a function of wavelength by monitoring the saturated absorption of chirped ultrafast pulses. The resulting nonlinear absorption spectrum becomes increasingly complex as the pulse is tuned to shorter wavelengths. However, fluorescence measurements indicate that the excited state population depends weakly on chirp when the pump wavelength is far from the lowest order electronic transition. Using a learning algorithm and closed-loop control, we find nonlinear chirp parameters that optimize features in the transmission spectrum. The results are discussed in terms of competition between excited state absorption and stimulated resonant Raman scattering.     

Reversible carboxamide-mediated internal activation at C(6) of 2-chloro-4-anilino-1H-pyrrolo[2,3-d]pyrimidines

A synthetic route to bisanilino-1H-pyrrolo[2,3-d]pyrimidines has been discovered, wherein the C(6)-chloride reactivity is necessarily enhanced via reversible acid-catalyzed internal activation of the pyrimidine ring by a C(1')-carboxamide moiety. Subsequent selective nucleophilic displacements at C(6) and C(1') constitute a one-pot tandem protocol for the rapid assembly of bisanilino-1H-pyrrolo[2,3-d]pyrimidines.     

Polymer complexes,XXIII: Synthesis and physico-chemical studies on transition metal complexes of symmetric novel poly(N,N′-o-phenylenediamine)-bis(cinnamaldehyde)

Summary New complexes derived from polymeric N,N-o-phenylenediamine bis(cinnamaldehyde) (L) with Cu^II, Co^II, Ni^II, Zn^II, UO ₂ ^II , and Pd^II were prepared and characterized by elemental analysis, magnetic susceptibilities and spectroscopic (IR, far-IR,¹H-NMR,¹³C-NMR and EPR) studies. A bidentate methine nitrogen atoms coordination of the ligand is assigned in the isolated complexes. The stereochemistries of the polymer complexes have been studied with using magnetic and spectroscopic measurements. Analytical data show 2:1 or 1:1 (ligand:metal) stoichiometry with water molecules coordinated to the Zn^II ion, as evidenced from IR and thermal analysis (DTA). The ligand was tested as a corrosion inhibitor for copper; the limiting concentration of the ligand to give maximum efficiency (60%) is 10^–3 mol dm^–3 at 25°C.

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Polymere Komplexe, XXIII: Synthese und physikalisch-chemische Untersuchungen an Übergangsmetallkomplexen von symmetrischem Poly(N,N-o-phenylendiamin)bis(zimtaldehyd)

Zusammenfassung Es wurden neue Komplexe von polymerem Poly(N,N-o-phenylendiamin)bis-(zimtaldehyd) mit Cu(II), Co(II), Ni(II), Zn(II), UO₂(II) und Pd(II) hergestellt und mittels Elementaranalyse, magnetischen Suszeptibilitätsmessungen und spektroskopischen Methoden (IR, far-IR,¹H-NMR,¹³C-NMR und EPR) charakterisiert. Es wurde eine zweizähnige Methin-Stickstoff-Koordination in den Komplexen festgestellt. Die Stereochemie der Polymerkomplexe wurde mittels magnetischer und spektroskopischer Messungen untersucht. Aus den analytischen Daten, mit zusätzlichen Argumenten aus IR und thermischer Analyse (DTA), ergab sich eine 2:1 oder 1:1 (Ligand:Metall)-Stöchiometrie mit an Zn(II) koordinierten Wassermolekülen. Der Ligand wurde als Korrosionsinhibitor für Kupfer getestet: die Grenzkonzentration des Liganden zur maximalen Effizienz (60%) ist 10^–3 mol dm^–1 bei 25°C.

     

Antibiotics Degradation and Bacteria Inactivation in Water by Cold Atmospheric Plasma Discharges Above and Below Water Surface

Plasma Chemistry and Plasma Processing - Cold atmospheric plasma discharges in air above air–water surface interface and discharges inside water with injection of air bubbles, show...     

Pyrrole functionalised metalloporphyrins as electrocatalysts for the oxidation of nitric oxide

Pyrrole-functionalised tetracarboxyphenyl porphyrin and trimethoxyphenylcarboxy-phenyl porphyrin containing Ni, Mn and Pd as the central metal ion were used to modify Pt-disk microelectrodes (∅ 50 μm) (by repetitive cyclic voltammetry, dip-dry and pulse-amperometry methods) for the detection of nitric oxide (NO). Electrodes modified with Mn(II) trimethoxyphenylcarboxyphenyl porphyrin using the pulse amperomery approach, were found to be sensitive, stable and fast in response towards the oxidation of NO. Thus, they were used for the detection of NO release from a population of transformed human umbilical vein endothelial cells (T-HUVEC) into a droplet of electrolyte solution following stimulation with vascular endothelial growth factor (VEGF). The electrode surface was covered with an additional layer of Nafion® to prevent interference from anionic molecules such as nitrite.