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The tellurium oxyanion tellurite is toxic for most organisms and it seems to alter a number of intracellular targets. In this work the toxic effects of tellurite upon Escherichia coli [4Fe-4S] cluster-containing dehydratases was studied. Reactive oxygen species (ROS)-sensitive fumarase A (FumA) and aconitase B (AcnB) as well as ROS-resistant fumarase C (FumC) and aconitase A (AcnA) were assayed in cell-free extracts from tellurite-exposed cells in both the presence and absence of oxygen. While over 90% of FumA and AcnB activities were lost in the presence of oxygen, no enzyme inactivation was observed in anaerobiosis. This result was not dependent upon protein biosynthesis, as determined using translation-arrested cells. Enzyme activity of purified FumA and AcnB was inhibited when exposed to an in vitro superoxide-generating, tellurite-reducing system (ITRS). No inhibitory effect was observed when tellurite was omitted from the ITRS. In vivo and in vitro reconstitution experiments with tellurite-damaged FumA and AcnB suggested that tellurite effects involve [Fe-S] cluster disabling. In fact, after exposing FumA to ITRS, released ferrous ion from the enzyme was demonstrated by spectroscopic analysis using the specific [Fe.sup.2+] chelator 2,2'-bipyridyl. Subsequent spectroscopic paramagnetic resonance analysis of FumA exposed to ITRS showed the characteristic signal of an oxidatively inactivated [[3Fe-4S].sup.+] cluster. These results suggest that tellurite inactivates enzymes of this kind via a superoxide-dependent disabling of their [4Fe-4S] catalytic clusters.

The evolution of defect structure and self-compensation is theoretically studied within quasichemical formalism in undoped and donor-doped Te-saturated CdTe during the cooling in the temperature interval 700[degrees]C-100[degrees]C. We show, that proper thermal treatment, including low temperature (cca 200[degrees]C) dwell, allows to prepare semi-insulating CdTe with deep level doping below the limit [10.sup.13] [cm.sup.-3], which is demanded in detector industry. New high-temperature transport data are used to refine on previous native defect properties for the modeling. Variant defect models are analyzed. Diffusion rates at lowered temperature are annotated to approve the model for real-time experimental verification. Index Terms--CdTe, deep defect, detector, self-compensation.

The synthesis and IR structural investigations of the novel compounds PbCl2.(SCH2CH2NH3), Pb(SCH2CH2NH2)(sub 2).2PbCl(SCH2CH2NH2), and Pb(SCH2CH2NH2)(sub 2) are reported. The ab initio quantum chemical calculations show that the Pb-N bonds are based on a sigma-type n(N)-6p(Pb) interaction, which dominates the pi-type n(sub p)(S)-6p(Pb) interaction and hence determines the molecular conformation.

The reactions of tellurium tetrahalides and triphenylphosphine in tetrahydrofuran under ambient conditions afford {(Ph3PO)2H}(sub 2)[Te2X10] [X = Cl, Br] and {(Ph3PO)(sub 3-)(OH3})2[TeI6]. The last species exhibits a structural framework similar to that of the tetramers in Gamma- and Delta-TeI4.

Scanning thermal microscopy is applied to investigate the local thermal properties of thin phase-change (Ge2Sb2Te2) layers. It is demonstrated that the heated tip can be used to locally crystallize parts of an amorphous Ge2Sb2Te2 layer, thereby suggesting thermal probes may be used for data storage applications on phase-change media.

The use of electrochemical deposition technique for the successful preparation of large area, uniform, continuous and ordered Bi(sub2)Te(sub3) is described. It is suggested that this technique could possibly help synthesize other metal, semimetal or semiconductor single crystal nanowire arrays.

A study of the uderpotential depostion (UPD) of Te monolayers onto Au electrodes from perchloric acid solution using electrochemical quartz microgravimetry (EQCM) and chronocoulometry is reported. Analysis of the current time data indicates that this process occurs by a two-dimensional instantaneous nucleation and growth mechanism, resulting in an ordered overlayer with a fractional coverage of ca. 0.41.

Research has been conducted on the chalcogeno-Diels-Alder reactions. The theoretical examination of the reactions between H (sub)2 C=X (X=S, Se, Te) and butadiene, ethylene and telluroacrolein, and thioformaldehyde and thioacrolein has been carried out.

Research on bifunctionalized vinyl tellurides paves the way for the stereo- and regioselective synthesis of vinyltellurides containing sulfonyl, phosphonyl, and iodo groups from stereo- and regiodefined addition of tellurides with alkynes. Data show that arylsulfinate serves as a sulfonyl radical precursor, while diaryl ditellurides as radical acceptors.

Researchers describe the isolation of the gutS gene in E. coli. This gene is induced by selenium and telluride, which are both toxic to living cells in high concentrations.

This article describes the high-performance liquid chromatography methodology for the isolation of kinetically and thermodynamically stabilized optically pure telluroxides. The stereochemistry of the compounds is S, as determined by rotations and circular dichroism spectra of telluroxides.

Novel three-dimensional tellurites, Na(sub.2)MTe(sub.4)O(sub.12) (M = W, Mo), having different types of intersecting tunnels are.discussed. They have been synthesized using hydrothermal and ceramic methods, and their structures have been studied using single-crystal X-ray diffraction. Three types of polyhedra were seen. One compound had novel spiral, sodium-containing hexagonal tunnels. Layered tellurites are noncentrosymmetric and have a nonzero second-harmonic generation response.

Research has been conducted on the tellurium diimide dimer. The use of THF as a solvent to synthesize this dimer is described.

Research has been conducted on the tellurium diimide dimer coordination complexes. Mono- and dimethylation of the complexes have been demonstrated via (super)1 H and (super)125 Te NMR spectroscopy.

Research has been conducted on the Rh-Te and Ir-Te binary systems. The use of Huckel calculations in investigating the systems' differences in phase and structure at low temperatures is described.

Research has been conducted on the O,O-alkylene dithiophosphate derivatives of halodimethyltellurium(IV). The synthesis of the compound by the reaction in dichloromehtane is described.

Research was conducted to examine the chemistry, spectroscopy, molecular structures and bonding properties of tellurium(II) dithiolates by experimental methods and ab initio calculations. Tellurium(IV) tetrathiolates, Te(SR)4, are thermodynamically unstable toward decomposition into tellurium(II) dithiolates, Te(SR)2 and S2R2. Tellurium(II) dithiolates have the ability to decompose to Te and S2R2 if heated or irradiated.

The behavior of the trapping times of minority carriers in In-doped CdTe films because of annealing and hydrogenation was examined through photoconductivity (PC) measurements on as-grown, annealed, hydrogenated, and hydrogenated and annealed In-doped CdTe epitaxial films grown on p-CdTe (211) substrates by molecular beam epitaxy. Results of the PC decay curve revealed a slow component with a time constant of a few milliseconds and this behavior was related to the presence of deep travel levels corresponding to minority carriers. The trapping times of the minority carriers were substantially decreased by the hydrogenation treatment.

The structure of Sc(sub 5)Ni(sub 2)Te(sub 2) prepared by high-temperature solid-state techniques was investigated. The structure contained pairs of eclipsed zigzag chains of nickel atoms that were coated by scandium atoms and demarcated from other chains by tellurium atoms. The structure was isotypic with that of Hf5Co(sub 1+x)P(sub 3-x) but shifted atomic positions and a different ordering of the main group and late transition elements gave it a clearly one-dimensional character.

A study was conducted to analyze the synthesis and crystal properties of three novel ternary manganese tellurides, namely, AmnTe2, Na3Mn4Te6 and NaMn(sub 1.56)Te2. The compounds were prepared by solid-state reaction and cation exchange methods in sealed Nb tubes. Experimental results indicated that AMnTe2 supported Curie-Weiss paramagnetism while the other two compounds exhibited paramagnetism with a weak dependence on temperature.

A novel, highly selective procedure for introducing organic sulfur, tellurium and selenium functions into vinylic cyclopropanes was described. The method was developed based on the relative reactivities of organic dichalcogenides and chalcogen-centered radicals. Experimental results showed that the reaction of vinylcyclopropanes with diphenyl disulfide and diphenyl diselenide occurs slowly to yield the corresponding gamma-(selenoethyl)allylic sulfides regioselectively upon irradiation with the light of wavelength over 300 nm. Vinylcyclopropanes also undergo regioselective thiotelluration via a novel (PhS)(sub 2)-(PhTe)(sub 2) binary system.

The synthesis and characterization of soluble chalcogenide (Et4N)4KAuAs4Te8 by crystal and electronic structure analysis were described. The ternary compound contains a square-planar gold cation and an unprecedented AuAs4Te8(5)- anion. The square-planar AuTe4 component of AuAs4Te8(5)- is analogous in structure to the square-planar TeTe4 unit of the As2Te5(2)- anion chain in (Et4N)2As2Te5. Furthermore, extraction reactions of ternary and quaternary alloys resulted in new ternary and quaternary Zintl anions.

The synthesis and characterization of four novel molybdenum-(IV) tellurite compounds including the two-dimensional tellurites ((NH4)2Mo3TeO12 and Cs2Mo3TeO12 and the 'zero-dimensional' tellurites Rb4Mo6Te2O24.6H20 and K4Mo6-Te2)24.6H2O using the hydrothermal methods are described. Results showed that an MoO4 layer whose motif is based on a slice of hexagonal tungsten oxide structure was present in the two-dimensional (Mo3TeO12)2- anion. It was also observed that while the layer was capped asymmetrically by tellurium on one side, the cations NH4+ and Cs+ were immobile.

Research was conducted on the asymmetric synthesis and the structure of pure telluronium salts by the reaction of chiral halooxatelluranes with alkyllithium. Another objective of the study was to determine the stereochemistry and possible mechanisms of the reaction in addition to their thermal and optical stability. Results revealed that synthesis of optically pure telluronium salts 4a-i can be achieved in high yield and selectivity by the reaction of chiral alkoxytelluranes 3a-i with organolithium and Grignard reagents.

A study was conducted to examine three selenium-containing iodothyronine deiodinases by reacting o,o'-diiodophenols under basic and acidic conditions with sodium hydrogen telluride, benzenetellurol, sodium hydrogen selenide. Sodium borohydride was utilized to minimize diphenyl diselenide and diphenyl ditelluride. Results indicated the possibility of locating reagents which support the selective mono or dideiodination of substrates.

The band structure of Cs3Te22 was studied by the ab initio tight-binding linear muffin-tin orbital technique, based on the density functional theory, to elucidate its structure and bonding. The computations were complemented by a study of the electronic density topology with the electron localization function and an orbital analysis utilizing the projected density states and the crystal orbital Hamiltonian population. Results showed that the short Te-Te contacts between Te8 rings and the defect Te6(super 3-) sheet in this compound have a direct impact on the characteristics of the material.

Research was conducted to investigate the feasibility of selective inhibition of cysteine proteases by taking advantage of the unique chemistry of organotellurium compounds with thiols. The interactions between cysteine in DMSO and Te derivatives were followed by 13C NMR and 125 Te. Te(IV) derivatives interacted with 4 equiv of cysteine and yielded new stable Te(IV) compounds while the Te(IV) compounds did not transform upon interaction with cysteine.

A study was conducted to analyze the electrodeposition of tellurium on a single-crystalline Au(111) electrode using 1064-nm-excited second harmonic measurements. The electrolyte solution was determined using purified water. A single-crystal disk was then utilized as an electrode. Experimental results indicated that the second harmonic rotational anisotropy changed with the first underpotential deposition of tellurium.

A new type of dicationic sigma-telluranes (eta4-tellane), (10-Te-4(C2X2))2+*2Y- (X = S or Se, Y = BF4 or CF3SO3) was prepared from the new flexible acryclic tris-chalcogenide, 2,6-bis((phenylthio)-methyl)phenyl phenyl telluride and 2,6-bis((phenylseleno)-methyl)phenyl phenyl telluride and the corresponding telluroxide through transannular bond formation. Based on single-crystal X-ray structure determinations, two apical sulfonio- or selenonio ligands bond to the central tellurium atom.

A study was conducted to examine the p-type doping of tellerium-based compounds and alloys during molecular beam epitaxy. Nitrogen atoms generated by a direct current glow plasma source were utilized to investigate the p-type doping. Results indicated that nitrogen doping introduced N(sub Te) shallow hydrogen acceptors. Findings also showed that nitrogen atoms induced substantial changes in the local lattice parameter of a ZnTe:N layer.

A research was conducted to study the cloning, sequence and inactivation of tellurite resistance determinants from Rhodobacter sphaeroides 2.4.1. Standard protocols were utilized for DNA isolation and recombinant DNA procedures while plasmids were characterized in biparental matings from Escherichia coli S17-1 strains into R. sphaeroides strains. Results showed that the disruption of the R. sphaeroides 2.4.1 cysK gene impaired tellurite resistance levels and suggested that there may be a link between cysteine biosynthesis and tellurite resistance.

Single crystals of [Cd.sub.0.8][Zn.sub.0.2]Te grown at the Institute of Solid State Physics, Chernogolovka, Russia, by the high-pressure vertical Bridgman method (HPVB) were mapped using X-ray fluorescence (XRF), X-ray diffraction (XRD), photoluminescence (PL), and leakage current measurements. Most of the Russian samples which we refer to as p-type CZT were more uniform in Zn composition than U.S. commercially produced material. The Russian material had a poorer crystallinity and, in the best case, could only count nuclear radiation. Differences in the material properties between Russian (p-type) and U.S. (n-type) material will be described. Index Terms - CdZnTe, high-pressure Bridgman.

The conversion of sulfonate esters of aziridinemethanols to allylic amines can be achieved using telluride ions acquired from tellerium. In this experiment, thin-layer chromatography was used to examine silica gel visualized by anisaldehyde, phosphomolybdic acid or ultraviolet light. The corresponding telluride reaction results to the formation of optically active allylic amines derived from optically active aziridinemethanols.

An experiment has been conducted to show the syntheses, characterizations and structures of the neutral and anionic complexes of tungsten telluride clusters. The mild oxidizing abilities of both sodium telluride and sodium ditelluride were the reasons for choosing the compounds as sources for tellurium. Infrared spectroscopy was used to identify coordinated organic ligands of tungsten telluride complexes. Because of their electronegativity differences, the electronic structures of selenium, sulfur and tellurium complexes were compared.

Dimethyltellurium and dithioformate complexes have been prepared and these complexes were characterized using elemental analysis and spectroscopies. The analysis included variable temperature studies. Te has an immediate environment which exhibits a sawhorse structure where the lone pair appears to be stereochemically active and is located in an equatorial position within a bipyramid of a distorted trigonal type. The coordination sphere also appears to contain the second sulfur atom.

The structure, synthesis, infrared absorption properties, electrical conductivity and thermoelectric power of the compound BaBiTe3 are discussed. The compound is described as one-dimensional and layered with slabs sandwiching Ba cations in pseudotrigonal prismatic sites. It is a narrow gap semiconductor that has one of the lowest lattice thermal conductivity values known for crystalline metal chalcogenides. Improvement of crystal quality and control of the level of dopants could greatly increase the thermoelectric performance of the compound.

The mixed tellurium/selenium Re6 clusters (NMe4)4(Re6(Te(sub 8-n)Se(sub n))(CN)6) (n=0 (1), n=1 (2), n=4 (3), n=7 (4) and n=8 (5)) were produced from the reactions of Re6Te15 with the required stoichiometry of NaCN and Se at 600 degrees C, followed by cation exchange with NMe4Br. These were synthesized by conventional solid state methods and were recrystallized after cation exchange. Compounds 1, 3 and 5 were characterized by single-crystal X-ray diffraction methods and the results on compound 3 stimulated the study of this series of compounds. The complications of cocrystallized mixtures, geometrical disorder and orientational disorder were observed.

Precursors to alloys such as Bi2S3Te2, Bi0.5Sb1.5Te3 and Bi1.8Sb0.2Se0.15Te2.85 were synthesized by aqueous coprecipitation and metal-organo complex techniques. The alloys were produced in fine-powder, polycrystalline form by hydrogen reduction of the precursors. Identification of the alloys was supported by total elemental analysis and X-ray diffraction data. The method is simpler than conventional melt processing and offers product yields in the 88 to 92% range.

The phases of composition of NbxRu6-xTe8 are synthesized and structurally characterized using X-ray powder diffraction with the Rietveld approach. The phases are prepared from elevated temperature reactions of stoichiometric mixtures of the elements in evacuated silica ampules. Nb3.33Ru2.67Te8 undergoes isotypic crystallization with Mo6Q8, where Q = S, Se, Te, to form rhombohedral crystals. The crystal structure is composed of M6Te8 mixed-metal clusters of Nb and Ru which form a three-dimensional network due to the linking of the intercluster M-Te bonds.

Tellumerates (MTe7)n- where n = 2,3 are achieved upon the reaction of appropriate metal substrates with polytelluride solutions in anhydrous N,N-dimethylformamide. The (HgTe7)2- anion, in both the NEt4+ and PPH4+, exhibits a similar structure with only a small discrepancy in the arrangement of the ligand. Anions (AgTe7)3- and (HgTe7)2- incorporate metal atoms that are in trigonal planar coordination to n(super 3)-Te(sub 7)(super4-). The central Te atom of such ligand forms a T-shaped assembly with two Te atoms and the metal atom.

Stereoselective hydrotelluration of terminal acetylenes gives Z-vinyl tellurides that react with organo-cuprates to produce Z-vinyl higher order cyanocuprates with a retention of double bond configuration. These cuprates react with alpha-beta unsaturated ketones and epoxides to form Z-4-vinyl-substituted ketones and Z-homoallylic alcohols, respectively. The ring opening of optically pure epoxide through transmetallation is stereospecific, which gives a single homoallylic stereoisomer.

The reaction between tert-BuNHLi and TeCl4 in a 4:1 ratio yields thermally stable Te-N compounds. The tellurium diimide dimer, Te2(Ntert-Bu)4, is bonded through an exocyclic nitrogen atom to LiTe(Ntert-Bu)2(NHtert-Bu), to form the most important centrosymmetric complex. The complexes have an ability to dimerize due to the presence of Te-N multiple bonds. The variable temperature 1H- and 7Li-NMR spectra and X-ray crystallography reveal some weak Te-N bonds since rapid proton shifts are observed. The mechanisms for the fluxional processes in these complexes is also discussed.

The reaction of an equimolar amount of dimethyltellurium dihalide and the potassium salt of O-methyl, O-ethyldithiocarbonic acid generates halodimethyl(O-alkyl dithiocarbonato)tellurium(IV) derivative with a 75-88% yield. The crystal structures of Me2TeCl(S2COEt) and Me2TeI(S2CO(i-Pr)) are analyzed by the Raman, infrared, and the 1H, 125Te and 13C NMR spectroscopy. The tellurium atom in both the complexes forms a sawhorse structure with stereochemically active lone pairs. The two methyl groups occupy equatorial positions, whereas halogen atoms occupy axial positions.

The gas phase and thermodynamic stabilities of the group 13 hydrides are determined by ab initio Moller-Plesset (MP2) calculations. Compounds In2H6 and Tl2H6 are found to be thermodynamically unstable in the gas phase and solid state but are kinetically stable in the gas phase. In2H6 exhibits thermodynamic stability only at low temperatures whereas the low thermodynamic stability of Tl2H6 are partly accounted to relativistic effects.

The synthesis of tellurium diimide dimers of the type RNTe(micro-NR')eTNR is presented. The scheme involves the reactions of the PN2Te heterocycle Ph2PN(SiMe3)2Te(Cl)NR (R= PPh2NSiMe3) with R'NHLi (R = tBu, tOct) and TeCl4 with tBuNHLi in a 1:4 molar ratio. Structural studies showed that the crystals of these dimers consist of a four-membered Te2Ne2 ring with the short, exocyclic Te=NR bonds arranged in either a cis or trans configuration.

The mixed metal carbonl telluride clusters (Phsub4P)sub2[ Fesub2MTesub3(CO)sub11] and Na(Etsub4N)sub2[Fesub3Wsub2Tesub8(TeMe)COsub12] where M = Mo,W are synthesized using mixtures of Fe(CO)sub12, M(CO)sub6 and Nasub2Tesub2 with Phsub4PBr in a sealed pyrex tube. The reaction is carried out metanothermally at 80 degree centigrade. The compound (Ph4P)2{Fe2MTe3(CO)11} crystallizes in monoclinic space group. The compound Na(Et4N)2{Fe3W2Te8(TeMe)CO12} has seven singlets. The hetrometallic cluster {Fe3W2Te8(TeMe)CO12} is a hybrid between {Fe4Te6(TeMe)2CO8}2- and {W6Te8(CO)18}2.

An approach is described for measuring electron self-exchange rate constants ([k.sub.11]) in solution based upon stable isotope-labeled reactants, chemical separations, and inductively coupled plasma mass spectrometry. The technique is demonstrated for the exchange between [Tl.sup.III] and [Tl.sup.I] aquo ions in aqueous HCl[O.sub.4]. [Tl.sup.III] is prepared using 203Tl-enriched [T1.sub.2][O.sub.3] (203Tl abundance, [approximately]36%), and [Tl.sup.I] is prepared from natural abundance Tl reagents (natural 203Tl abundance, 29.52%). The exchange is monitored by mixing the labeled and unlabeled reactants and performing timewise separations through selective precipitation of [Tl.sup.I] as TlBr. Isotope abundances are measured in the TlBr precipitate and [Tl.sup.III] solution phases using ICPMS with minimal sample preparation; an NIST 981 (common lead) spike is added, and the 208Pb/206pb is measured as an internal standard to correct for mass discrimination. The self-exchange rate constant is determined from a McKay plot obtained from the 205Tl abundances of either oxidation state. A [k.sub.11] of (1.0 [+ or -] 0.1) x [10.sup.-4] [M.sup.-1] [S.sup.-1] was obtained in 1.5 M aqueous HCIO4 at 25 [degrees] C. The obtained [k.sub.11] compares favorably to a value of 1.1 x [10.sup.-4] [M.sup.-1] [s.sup.-1] based upon a previously published study of this exchange reaction using radiolabeled (204Tl) reactants.

The rigidity and stability of (Ag2Te2)(super 2-) layers and their tetragonal symmetry are most likely responsible for K(sub 0.33)Ba(sub 0.67)AgTe2 stabilization. Electron diffraction measurements indicate the presence of an incommensurate orthorhombic and a commensurate tetragonal superstructure. The structure, synthesis, and band-structure analysis of K(sub 0.33)Ba(sub 0.67)AgTe2 are discussed.

Geometric analyses of the synthesized Te(OTeF5)4, FTe(OTeF5)4- and Te(OTeF5)5- anions shows that steric interactions between OTeF5 groups do not affect the geometries of the anions. Pseudo-octahedral patterns are seen in the single atom and ligand atoms binding with Te(super IV). Structural details of the anions are discussed. Results of the study reveal the Lewis acid properties of five coordinate Te(super IV) in Te(OTeF5)4. Raman spectra and crystal structures of the solid Te(OTeF5)4 and N(CH3)4+ are presented. The Lewis acid behavior of Te(OTeF5)4 for the OTeF5- anion was also studied.