硒的分析方法研究

硒是一种分散的稀有元素，它在电子工业，医疗等部门有广泛的用途和诱人的发展前景。本文介绍了一些硒的定性和定量分析方法。     

Regioselective synthesis of symmetrical pyridyl selenium compounds by bromine–magnesium exchange of bromopyridines using isopropyl magnesium chloride: X‐ray crystal structure of 2,2′,5,5′‐tetrabromo‐3,3′‐dipyridyldiselenide

2,2′‐Dipyridyl‐3,3′‐dipyridyl,5,5′‐dipyridyl‐diselenides have been synthesized by a convenient method employing non‐cryogenic conditions. Various bromopyridines (2‐Bromopyridine, 2,5‐dibromopyridines and 2,3,5‐Tribromopyridines) undergo selective monobromine–magnesium exchange to yield the corresponding pyridyl magnesium chlorides at room temperature upon treatment with ⁱPrMgCl. The resulting pyridyl magnesium chloride is quenched with elemental selenium, which upon further oxidation affords the above diselenides in good yields. The compounds prepared using this methodology have been characterized by elemental analysis, IR, NMR (¹H, ¹³C, ⁷⁷Se) and mass spectral analysis. The molecular structure of 2,2′,5,5′‐Tetrabromo‐3,3′‐dipyridyldiselenide has been established by single‐crystal X‐ray diffraction analysis. It exists as a dimeric form due to the non‐bonding interactions between the selenium of one pyridine moiety and the hydrogen of the other. Copyright © 2004 John Wiley & Sons, Ltd.     

The synthesis,crystal structures and SOD activities of a new ligand (Lse) and Co(Lse)2(SCN)2 complex [Lse = selenium ether bis‐(N‐1‐methyl‐ benzotriazole)]

A new ligand containing selenium, Se (CH₂‐N‐Btrzole)₂ (L^se) (Btrzole = benzotriazole) and its cobalt(II) complex, Co(L^se)₂(SCN)₂, have been synthesized and the molecular structures of the title compounds have been determined by X‐ray techniques. The L^se is a meso‐configuration with a symmetric plane through the Se center, the intermolecular weak interactions of Se? Se, Se? N and π? π stacking between benzotriazole rings to extend the molecular structure to two‐dimensional network configuration. In the Co(II) complex, the metal center is in a six‐coordinated octahedral environment. Two Co(II) atoms are linked by two ligands to form a 20‐membered macrocycle; the adjacent macrocycles are linked by coordinated bond of Co? N_bentrozole to extend an infinite double strained chain. The SOD activity of the ligand and Co(II) complex have been studied by using the pyrogallol autoxidation method; thermal properties and luminescent properties of Co(II) complex have been tested, and the details of those properties have been discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

A new approach to the synthesis of 2-vinylthiophenes and selenophenes; competition between free radical and anionic cycloaromatization of bridged di- and tetrapropargylic sulfides and selenides

A series of unknown di- and tetrapropargylic sulfides and selenides have been prepared. In the presence of t-BuOK in dry THF these compounds underwent isomerization to the corresponding diallenes, followed by a tandem anionic cyclization and aromatization to 2-vinylthiophene or selenophene derivatives. Some mechanistic studies indicated competition between free radical and anionic cycloaromatization. The latter is influenced by the nature of the bridging heteroatom, substitution of the allenyl group and base concentration.     

Application of arsenic to electrophotoreceptors

Arsenic has been applied to many electronic devices such as electrophotoreceptors, gallium arsenide (GaAs) semiconductors and solid-state image pickup devices. For electrophotoreceptors selenium–arsenic (Se? As) alloys are coated onto the conductive substrate of the receptors. Arsenic is mostly used in electophotoreceptors in electronic devices. During the coating process, a part of the gaseous arsenic is released through an exhaust system. In order to avoid arsenic being discharged to the atmosphere, bag filters and high-efficiency particulate air filters are set before the exhaust port. Any arsenic which still exists in the waste water after washing tools and jigs from the coating process is collected by sedimentation before discharging. The Ames salmonella/microsome plate test for As₂Se₃ indicated no mutagenic activity under the test system used. For the safety of workers engaged in arsenic-related jobs, they received a medical examination once every six months. No negative trends from the examination was found in 428 men who received the examination from Autumn 1980 to Spring 1987.     

Anwendung niederenergetischer Gammastrahler für radiographische Untersuchungen

An die zerstörungsfreie Materialprüfung mit Isotopen werden in unserem Lande erweiterte Forderungen gestellt, die sowohl die Prüfung von dünnwandigem Stahl als auch die Prüfung von Leichtmetallerzeugnissen beinhalten. Die Forderungen ergaben sich auf dem Gebiet, wo die Vorteile der γ-Defektoskopie im Vergleich mit der Röntgenprüfung in den Vordergrund treten. Die Strahlungsquellen Se-75 und Tm-170 schienen zu diesem Zweck die geeignetsten zu sein.     

Ebselen and Analogues: Pharmacological Properties and Synthetic Strategies for Their Preparation

Ebselen is the leader of selenorganic compounds, and starting from its identification as mimetic of the key antioxidant enzyme glutathione peroxidase, several papers have appeared in literature claiming its biological activities. It was the subject of several clinical trials and it is currently in clinical evaluation for the treatment of COVID-19 patients. Given our interest in the synthesis and pharmacological evaluation of selenorganic derivatives with this review, we aimed to collect all the papers focused on the biological evaluation of ebselen and its close analogues, covering the timeline between 2016 and most of 2021. Our analysis evidences that, even if it lacks specificity when tested in vitro, being able to bind to every reactive cysteine, it proved to be always well tolerated in vivo, exerting no sign of toxicity whatever the administered doses. Besides, looking at the literature, we realized that no review article dealing with the synthetic approaches for the construction of the benzo[d][1,2]-selenazol-3(2H)-one scaffold is available; thus, a section of the present review article is completely devoted to this specific topic.     

Controlled synthesis of selenium of different morphologies at room temperature

A facile and convenient chemical precipitation route has been developed for the controlled growth of selenium nanowires and hierarchical microspheres at room temperature, with Na₂SeO₃ and hydrazine hydrate as starting materials in the presence of 1,2,3‐trimethylimidazolium tetrafluoroborate (tmimBF₄). The surface morphology of microspheres can be tuned by adjusting the reaction media. The products were characterized by X‐ray powder diffraction (XRD) and scanning electron microscope (SEM). Possible formation mechanisms of selenium nanowires and microspheres are proposed, respectively. The influences of the nature of reaction media, agitation and tmimBF₄ on the morphologies development were experimentally investigated and it was found that these factors were of great importance for the formation of Se morphologies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)