Spectral properties of neutral selenium and tellurium. A relativistic treatment

Oscillator strengths for fine‐structure transitions in the complex atomic systems, neutral selenium, and tellurium, are reported. The calculations were carried out using the relativistic quantum defect orbital method. The resulting oscillator strengths are analyzed in terms of other theoretical and experimental data. In addition, to estimate the correctness of our oscillator strengths for these species, we have also analyzed the regularities complied by the calculated f‐values. © 2001 John Wiley & Sons, Inc. Int J Quant Chem, 2001     

Chemical vapour deposition of selenium and tellurium films by UV laser photolysis of selenophene and tellurophene

Excimer laser‐induced photolysis of gaseous selenophene and tellurophene affords gaseous 1‐buten‐3‐yne and ethyne (as major products) and butadiyne (a very minor product) and results in chemical vapour deposition of selenium and tellurium films. The film properties were characterized by XPS and SEM techniques and by UV spectroscopy. Copyright © 2000 John Wiley & Sons, Ltd.     

Regioselective reactions of sulfur, selenium and tellurium chlorides with allyl trimethyl silane

Electrophilic addition of SCl₂, SeCl₂ and SeCl₄ to 2 equivalents of allyl trimethyl silane proceeds regioselectively to give bis[2-chloro-3-(trimethylsilyl)propyl] sulfide, selenide and selenium dichloride, respectively. The reaction with TeCl₄ affords only diallyl tellurium dichloride. The structures of the compounds were confirmed by ¹H, ¹³C, ⁷⁷Se and ¹²⁵Te NMR techniques.     

Four related diethyl [(arylamino)(4‐ethynylphenyl)methyl]phosphonates

Crystal structures are reported for four related diethyl [(arylamino)(4‐ethynylphenyl)lmethyl]phosphonate derivatives, namely diethyl [(4‐bromoanilino)(4‐ethynylphenyl)methyl]phosphonate, C₁₉H₂₁BrNO₃P, (I), diethyl ((4‐chloro‐2‐methylanilino){4‐[2‐(trimethylsilyl)ethynyl]phenyl}methyl)phosphonate, C₂₃H₃₁ClNO₃PSi, (II), diethyl ((4‐fluoroanilino){4‐[2‐(trimethylsilyl)ethynyl]phenyl}methyl)phosphonate, C₂₂H₂₉FNO₃PSi, (III), and diethyl [(4‐ethynylphenyl)(naphthalen‐2‐ylamino)methyl]phosphonate, C₂₃H₂₄NO₃P, (IV). The conformation of the anilinobenzyl group is very similar in all four compounds. The P—C bond has an approximately staggered conformation, with the aniline and ethynylphenyl groups in gauche positions with respect to the P=O double bond. The two six‐membered rings are almost perpendicular. The sums of the valence angles about the N atoms vary from 344 (2) to 351 (2)°. In the crystal structures, molecules of (I), (III) and (IV) are arranged as centrosymmetric or pseudocentrosymmetric dimers connected by two N—H...O=P hydrogen bonds. The molecules of (II) are arranged as centrosymmetric dimers connected by C_methyl—H...O=P hydrogen bonds. The N—H bond of (II) is not involved in hydrogen bonding.     

Theoretical study of selenium and tellurium impurities in (ZnO)6 clusters using DFT and TDDFT

Zinc oxide (ZnO) nanostructures have attracted much interest due to their potential applications in various fields including optoelectronics, glass industries, and solar cells. These compounds hold the promise of creating new materials that can advance energy technologies. In this work, a series of (ZnO)₆ clusters with selenium and tellurium applied as substitutional impurities has been studied. The investigated structures have been produced through the doping of (ZnO)₆ clusters by replacing an oxygen atom with a selenium or a tellurium atom at each time. The ground state geometric parameters of (ZnO)₆ structures, containing selenium or tellurium atoms as substitutional impurities, were calculated using density functional theory (DFT) with B3LYP and LanL2DZ basis set. Excited state energies and absorption wavelengths were computed using time‐dependent‐DFT (TDDFT). For the calculation of emission wavelengths, Hartree–Fock configuration interaction singles (HF/CIS) has been used in order to perform the excited state geometry optimization. This work led to some important results that can be helpful for developing novel THz sensitive materials and imaging detectors that may be an alternative to x‐rays detectors for radiology as well as for the development of solar cells and electroluminescent diodes. Zinc oxide (ZnO) nanostructures have attracted growing interest due to their potential applications in many technological fields, including optoelectronics, the glass industry, and energy. The presence of impurities, in particular selenium and tellurium, in ZnO‐based clusters can affect their structural and spectroscopic properties. Some of these doped nanostructures have favorable Terahertz emission characteristics that make them good candidates for applications in biology and medicine.     

Synthesis and polycondensation of some new organic tellurium compounds containing mono- and di-amino groups

Several new and known organic tellurium compounds containing amino groups (i.e. ArTeBr₃, Ar₂Te₂ and Ar₂Te, where Ar= 4-NH₂C₆H₄, 2-NH₂C₆H₄, 4-CH₃CONHC₆H₄ or 2-NH₂-5-NO₂-C₆H₃) were prepared by reacting aminoarylmercury chlorides with tellurium tetrabromide in glacial acetic acid. Bis(4-aminophenyl) telluride and bis(2-amino-5-nitrophenyl) telluride were polymerized with aromatic and aliphatic diacid chlorides (i.e. terephthaloyl chloride and sebacoyl chloride), as well as with toluene di-isocyanate, leading to new organic tellurium polyamides and polyurea. All organic tellurium compounds and their condensation polymers were characterized by elemental analyses, IR, ¹H and ¹³C NMR, and mass spectroscopy. The thermal stabilities of the resulting polymers were determined by thermogravimetric and derivative thermogravimetric techniques. © 1998 John Wiley & Sons, Ltd.     

Donor Acceptor Complexes between the Chalcogen Fluorides SF2, SeF2, SeF4 and TeF4 and an N-Heterocyclic Carbene

The majority of binary chalcogen fluorides are fiercely reactive and extremely difficult to handle. Here, we show that access to crystalline donor-acceptor complexes between chalcogen difluorides (sulfur, selenium) and tetrafluorides (selenium, tellurium) with the N-heterocyclic carbene (NHC) 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) is possible conveniently and safely without the need to generate the highly unstable EF₂ (E=S, Se) or the very toxic and corrosive SeF₄.     

Neutral tellurium rings in the coordination polymers [Ru(Te9)](InCl4)2, [Ru(Te8)]Cl2, and [Rh(Te6)]Cl3

Shiny black, air‐insensitive crystals of tellurium‐rich one‐dimensional coordination polymers were synthesized by melting a mixture of the elements with TeCl₄. The compounds [Ru(Te₉)](InCl₄)₂ and [Ru(Te₈)]Cl₂ crystallize in the monoclinic space group type C2/c, whereas [Rh(Te₆)]Cl₃ adopts the trigonal space group type R$\bar 3Shiny black, air-insensitive crystals of tellurium-rich one-dimensional coordination polymers were synthesized by melting a mixture of the elements with TeCl(4). The compounds [Ru(Te(9))](InCl(4))(2) and [Ru(Te(8))]Cl(2) crystallize in the monoclinic space group type C2/c, whereas [Rh(Te(6))]Cl(3) adopts the trigonal space group type R ?3c. In the crystal structures, linear, positively charged [M(m+) (Te(n)(±0))] (M=Ru, m=2; Rh, m=3) chains run parallel to the c axes. Each of the uncharged Te(n) molecules (n=6, 8, 9) coordinates two transition-metal atoms as a bridging bis-tridentate ligand. Because the coordinating tellurium atoms act as electron-pair donors, the 18-electron rule is fulfilled for the octahedrally coordinated transition-metal cations. Based on DFT calculations, the quantum theory of atoms in molecules (QTAIM) and the electron localizability indicator (ELI) provide insight into the principles of the polar donor bonding in these complexes. Comparison with optimized ring geometries reveals substantial tension in the coordinating tellurium molecules.     

Simultaneous determination of inorganic arsenic,antimony, selenium and tellurium by ICP-MS in environmental waters using SPE preconcentration on modified silica

This paper deals with a simplified multi-element profiling of inorganic arsenic, antimony, selenium and tellurium in the form of ⁷⁵As, ⁸²Se, ¹²¹Sb and ¹²⁵Te by ICP-MS for amounts less than 10?µg?L^?1. Internal standards such as ⁷²Ge and ²⁰⁹Bi were successfully used for the suppression of both influence of macro elements Na⁺, K⁺, Ca²⁺, Mg²⁺ or Al³⁺, and interference of limited concentrations of heavy metal ions. Modified silica sorbents Separon? SGX C18, C8, CN, NH₂, RPS and Phenyl were tested for the preconcentration of As, Sb, Se and Te (0.25–5?µg?L^?1) in the form of ion associates with cationic surfactants from 50–250?mL sample volume. 1-etoxycarbonyl-pentadecyltrimethylammonium bromide (Septonex®, 0.005?mol?L^?1) was suitable for this purpose in the presence of 4-(2-pyridylazo) resorcinol, 2-pyrrolidinecarbodithioate and 8-hydroxyquinoline-5-sulphonic acid. The quantitative retention occurred at pH 7?±?0.2 and the mixture of acetone with ethanol in ratio 1?:?1 in the presence of 0.1?mol?L^?1 HCl was used for the quantitative elution. Organic solvents and the excess of acid were removed by evaporation prior to the determination by ICP-MS. The determination of the above trace metalloids in various kinds of water with enrichment factor till 50 times on silica Separon? SGX C18 and the above reagents were compared with the standard addition method.     

A square‐planar tellurium(II) complex with Te,Te′‐chelating ligands

While exploring the chemistry of tellurium‐containing dichalcogenidoimidodiphosphinate ligands, the first all‐tellurium member of a series of related square‐planar E^II(E′)₄ complexes (E and E′ are group 16 elements), namely bis(P,P,P′,P′‐tetraphenylditelluridoimidodiphosphinato‐κ²Te,Te′)tellurium(II) (systematic name: 2,2,4,4,8,8,10,10‐octaphenyl‐1λ³,5,6λ⁴,7λ³,11‐pentatellura‐3,9‐diaza‐2λ⁵,4λ⁵,8λ⁵,10λ⁵‐tetraphosphaspiro[5.5]undeca‐1,3,7,9‐tetraene), C₄₈H₄₀N₂P₄Te₅, was obtained unexpectedly. The formally Te^II centre is situated on a crystallographic inversion centre and is Te,Te′‐chelated to two anionic [(TePPh₂)₂N]⁻ ligands in an anti conformation. The central Te^II(Te)₄ unit is approximately square planar [Te—Te—Te = 93.51 (3) and 86.49 (3)°], with Te—Te bond lengths of 2.9806 (6) and 2.9978 (9) Å.     

Differential titrimetric determination of mixtures of selenium and tellurium

Methods are described for the differential titrimetric determination at room temperature of mixtures of selenium(IV) and tellurium(IV). The test solution in 0.75-3.5M condensed phosphoric acid medium is oxidized with an excess of permanganate and the unreacted permanganate is titrated with iron(n), with ferroin as indicator, to indicate the total content of selenium and tellurium present. Then 10-20 ml of 10M sulphuric acid, 0.4 ml of 0.1% osmium tetroxide solution and an excess of arsenic(III) are added to the same solution and the unreacted arsenic(III) is titrated with permanganate (ferroin as indicator) to indicate the content of tellurium.     

A Regioselective Synthesis of Novel Functionalized Organochalcogen Compounds by Chalcogenocyclofunctionalization Reactions Based on Chalcogen Halides and Natural Products

The regioselective synthesis of novel functionalized condensed organochalcogen compounds by chalcogenocyclofunctionalization reactions based on chalcogen halides and the natural products thymol and carvacrol has been developed. The reactions of selenium dibromide with allyl thymol and allyl carvacrol proceeded in methylene chloride at room temperature in the presence of NaHCO₃ affording bis[(7-isopropyl-4-methyl-2,3-dihydro-1-benzofuran-2-yl)methyl] and bis[(4-isopropyl-7-methyl-2,3-dihydro-1-benzofuran-2-yl)methyl] selenides in 90–92% yield. Similar sulfides were obtained in 70–72% yields by the reaction of sulfur dichloride in chloroform under reflux. Trihalotellanes containing the same organic moieties were synthesized from allyl thymol, allyl carvacrol and tellurium tetrachloride or tetrabromide in quantitative yields. Corresponding functionalized ditellurides were prepared in 91–92% yields by the reduction of the trichlorotellanes with sodium metabisulfite in two-phase solvent system. The comparison of reactivity of sulfur, selenium and tellurium halides in chalcogenocyclofunctionalization and distinguishing features of each reaction were discussed.     

Separation of selenium(IV) and tellurium(IV) from mixtures by extraction chromatography with trioctylphosphine oxide

The reversed-phase extraction chromatographic separation of selenium(IV) and tellurium(IV) from several elements with trioctylphosphine oxide as extractant is reported. Selenium was extracted from 6M hydrochloric acid containing 7M lithium chloride was stripped with 4M hydrochloric acid, and tellurium was extracted from either the same medium as selenium or from 4M hydrochloric acid, and stripped with 1-2M hydrochloric acid. Selenium and tellurium can be separated from multicomponent mixtures.     

Reactions of β-diketiminates with selenium and tellurium halides

The complexes [nacnacTeCl₄] and nacnacSeCl⁺Cl⁻ (nacnac = [{N(C₆H₃ⁱPr₂2,6)C(Me)}₂CH]⁻) have been prepared in good yields and characterized in the solid state by X-ray crystallography. The crystals of both compounds show C-H activation of the ligand backbone. In the case of tellurium, no LiCl displacement or nitrogen chelation is observed and an ionic TeCl₄ complex is isolated. By contrast, under similar reaction conditions, the reaction with SeCl₄, affords a cationic Se(II) complex with loss of four chlorines and rearrangement of the chloride atom to the nacnac ligand.     

Anti‐cancer potential of selenium‐ and tellurium‐containing species: opportunities abound!

An overview highlighting the anti‐cancer potential of (bio‐essential) selenium‐ and tellurium‐containing species, with an emphasis on biological targets and mechanisms of action, is presented. Studies thus far have focused on selenium(II) compounds (along with – to a lesser extent – inorganic selenium and selenium nanoparticles) which often successfully exploit the inherent anti‐oxidizing ability of selenium. Significantly less work has been conducted in developing anti‐cancer tellurium compounds, yet two tellurium(IV) species are proven, clinically, as anti‐cancer agents. Given the prevalence of the disease and the accumulated insights into mechanisms of action, the continued development of selenium‐ and tellurium‐containing molecules is an area deserving greater attention. Copyright © 2012 John Wiley & Sons, Ltd.     

The Reaction of Organo-Selenium and -Tellurium Compounds with Dihalogens,Interhalogens, and Pseudohalogens

Adducts of selenium and tellurium donor molecules with dihalogens, interhalogens, and pseudohalogens exhibit a remarkable structural diversity. Some interesting examples of these materials and key factors influencing their formation, structures, and bonding are discussed.     

The application of thiosalts in analysis : Estimations based on decomposition of thiosalts Part A. Estimation of arsenic,selenium and tellurium

1. It has been shown that the complete precipitation of arsenic sulphide (from arsenates) by decomposing the thiosalt provides a, lemarkably convenient and rapid method for its estimation which is in marked contrast to the tedious methods so far available for this purpose. 2. The method of precipitating the sulphide bv decomposing the thiosalt is also applicable to the estimation of tellurium for which no perfectly iclicibic gravimetric method had so far been devised. 3. Selenium also can be estimated gi avimetrically by this method and it provides a convenient alternative to the well-known method based upon I eduction to the metal. 4. The precipitates obtained in the case of arscnic, tellurium, and selenium correspond to the formulae As₂S₅, TeS₂ and SeS₂, respectively.     

The Determination of Trace Amounts of Tellurium and Selenium in Gallium Metal

Abstract

Analytical methods have been developed for the separation, concentration and determination of trace quantities of tellurium and selenium from primary and scrap gallium metal. A chloroform extraction is made of the tellurium diethyldithiocarbamate complex at a pH of 8.5. This extraction, in the presence of ammonium citrate, allows the satisfactory determination of tellurium by emission or atomic absorption spectrohcopy. The limit of sensitivity of the method is 0.5 pg of tellurium in 1.0 gram of gallium (0.5 ppm Te).     

Extraction,Spectrophotometric, and Atomic Absorption Spectrophotometric Determination of Selenium With N-Phenylbenzohydroxamic Acid

Abstract

Solvent extraction spectrophotometric and atomic absorption spectrophotometric methods for the determination of selenium(IV) in microgram quantities are described. The selenium(IV) forms yellow colored complex with N-phenylbenzohydroxamic acid (PBHA) extractable into chloroform from 7 M HClO₄. Se-PBHA complex has maximum absorbance at 345 nm with a molar absorptivity 1.5 × 10⁵ 1 mol^?1 cm^?1 and Sandell's sensitivity 0.000526 μg /cm². Effect of molarity, reagent concentration, diverse ions on the extraction of selenium complex were studied. The selenium is determined in presence of tellurium.