Tellurium Nuclei Research Articles

Understanding 125Te NMR chemical shifts in disymmetric organo-telluride compounds from natural chemical shift analysis.

Organotellurium compounds of general formula X-Te-R display a broad range of chemical shifts that are very sensitive to the X and R substituents. In order to link the 125Te chemical shift of a series of perfluoroalkyl aryl tellurides to their electronic structure, the chemical shielding tensors of the 125Te nuclei were calculated by density functional theory (DFT) and further analyzed by a decomposition into contributions of natural localized molecular orbitals (NLMOs). The analysis indicated that the variation in 125Te chemical shifts in molecules 1-13 is mainly due to the magnetic coupling of the tellurium p-character lone pair with antibonding orbitals perpendicular to it {σ*(Te-X) and σ*(Te-C(Ar))} upon action of an external magnetic field. The strength of the coupling is affected by electronic properties of the X-substituents, polarization of the antibonding orbitals and presence of secondary interactions perturbing the energy of these orbitals. The lower in energy and the more polarized towards tellurium the antibonding orbitals are, the stronger is the coupling and the more deshielded the tellurium nucleus.

Sulforaphane-assisted preparation of tellurium flower-like nanoparticles

A new method for the fabrication of flower-like tellurium nanoparticles is reported. It is based on the reduction of tellurite precursor by products generated during decomposition of sulforaphane at elevated temperature in aqueous medium. These species and other organic molecules present in the reaction mixture are being adsorbed on the surface of tellurium nuclei and govern further tellurium growth in the form of nanoflowers. The obtained particles have been characterized by a range of physicochemical techniques. It was shown that the average size of the nanoflower particles is ca. 112 nm, and they are composed of smaller domains which are ca. 30 nm in diameter. The domains are crystalline and consist of trigonal tellurium as shown by x-ray diffraction, Raman spectroscopy and high resolution transmission electron microscopy. The tellurium nanoflowers were examined from the perspective of their potential anticancer activity. The in vitro cell viability studies were conducted on breast cancer (MDA-MB-231, MCF-7) and normal cell lines (MCF-10A) employing MTT and CVS assays. It was shown, that the nanoflowers exhibit considerable cytotoxicity against cancer cells which is ca. 3–7 times higher than that observed for reference normal cells. The preliminary in vivo investigations on rats revealed that the nanoflowers accumulate predominantly in pancreas after intraperitoneal administration, without observable negative behavioral effects.

Hierarchical Basis Sets for the Calculation of Nuclear Magnetic Resonance Spin-Spin Coupling Constants Involving Either Selenium or Tellurium Nuclei.

New basis sets, acvXz-J (X = 2, 3, 4), were designed for tellurium and selenium atoms for the calculation of indirect nuclear spin-spin coupling constants involving selenium or tellurium nuclei. Saturation of angular spaces was performed in an even-tempered manner till achieving the convergence of spin-spin coupling constants under consideration. The high-accuracy correlated SOPPA(CCSD) method was employed in this procedure. Saturated basis sets were contracted by approximately 30% using the coefficients obtained from the atomic self-consistent field (SCF) closed-shell calculations of selenium and tellurium anions, Se2- and Te2-. Final basis sets of acvXz-J showed sufficiently high accuracy in comparison with previous special basis sets.

NMR study of topological insulator Bi2Te3 in a wide temperature range

NMR studies of 125Te in the topological insulator bismuth telluride Bi2Te3 in a wide temperature range from room temperature to 12.5 K are performed. The pulsed NMR spectrometer Bruker Avance 400 is applied. The NMR spectra are obtained for the powder from Bi2Te3 single crystal and monocrystalline plates with the orientations c || B and c ⊥ B. At room temperature, the spectra consist of two lines related to two nonequivalent positions of tellurium nuclei Te1 and Te2. The parameters of the NMR frequency shift tensor are found from the powder spectrum. The temperature dependences of the spectra for the powder and plates with the orientation c ⊥ B agree with each other. The line shift with decreasing temperature is explained by the reduction of the Knight shift. The thermal activation energy of charge carriers is estimated. The spectra for the plates with the orientation c || B demonstrate peculiar behavior below 91 K. The spin-lattice relaxation time for the powder and monocrystalline plates with both orientations at room temperature is measured.

NMR studies of single crystals of the topological insulator Bi2Te3 at low temperatures

A powder sample and single-crystal plates of the topological insulator Bi2Te3 have been investigated using the 125Te NMR method at room temperature and at low temperatures in the range from 12.5 to 16.5 K. The NMR spectra of the single-crystal plates have been studied in the orientation where the crystallographic axis c is directed parallel or perpendicular to the magnetic field. The spectra have been obtained by means of recording spin-echo signals and plotting their envelopes. It has been shown that the NMR spectra for the bismuth telluride powder and plates with the orientation c ⊥ B consist of two lines, which are presumably attributed to tellurium nuclei in two crystallographic positions in the bulk of the sample. The position and shape of the lines are determined by the chemical shift and the Knight shift. For the orientation of the plates c || B, the spectrum contains an additional component in the high-frequency region, which cannot appear due to the angular dependence of the line shifts caused by tellurium nuclei in the bulk of the topological insulator. At a low temperature, the additional line dominates in the spectrum.

Synthesis and Characterization of High-Purity Tellurium Nanowires via Self-seed-Assisted Growth Approach

Nanowires have attracted intense attention in recent years due to their novel physical properties. In this work, we prepare high-purity tellurium nanowires through the self-seed-assisted growth method previously developed by us. The tellurium seeds were firstly synthesized by reducing Na2TeO3 in the ice water with NaBH4. The high-purity tellurium nanowires with a diameter of 40–50 nm and a length of several tens of micrometers were then grown on tellurium seeds by reducing Na2TeO3 with hydrazine hydrate. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were employed to characterize the crystal structure, microstructure, and growth direction of tellurium seeds and nanowires. The effects of temperature, time, surfactant and tellurium seeds on microstructures of tellurium nanowires has also been investigated. The synthesis conditions of tellurium seeds and nanowires was optimized. The selected area electron diffraction pattern confirms that the growth direction of tellurium nanowires is parallel to [0001] direction. It was discovered that high-purity tellurium nanowires with high aspect ratio can be synthesized by precisely controlling the temperature to adjust the nucleation rate of the tellurium nuclei, selecting the appropriate surfactant to induce the coordination along the macromolecular chain, and using tellurium seeds as the templates of the epitaxial growth of tellurium nuclei.

High resolution (3He,t) experiment on the double-βdecaying nuclei128Te and130Te

Gamow-Teller (GT) strength distributions have been investigated in a high-resolution (${}^{3}$He,$t$) charge-exchange experiment on the double-$\ensuremath{\beta}$ ($\ensuremath{\beta}\ensuremath{\beta}$ ) decaying nuclei ${}^{128}$Te and ${}^{130}$Te. The experiment was carried out at the Research Center for Nuclear Physics, Osaka, with a 420-MeV incident ${}^{3}$He beam and the Grand Raiden magnetic spectrometer. A final-state energy resolution of 35 keV was achieved. The extracted GT strength distributions at low excitation energies in the final nuclei ${}^{128}$I and ${}^{130}$I are presented and discussed in the context of the $\ensuremath{\beta}\ensuremath{\beta}$ decay matrix elements for the two tellurium nuclei. The additional neutron pair in ${}^{130}$Te seems to produce a moderate increase in the fragmentation of the low-energy GT distribution.

Fragmentation of mixed-symmetry excitations in stable even-even tellurium nuclei

The lowest six excited ${2}^{+}$ levels of the even-even $^{122\ensuremath{-}130}\mathrm{Te}$ nuclei have been investigated using \ensuremath{\gamma}-ray spectroscopy following inelastic neutron scattering. These levels have been identified and their decay properties have been characterized from \ensuremath{\gamma}-ray excitation functions and \ensuremath{\gamma}-ray angular distributions; additionally, lifetimes of these levels have been deduced using the Doppler-shift attenuation method. Electromagnetic transition rates and $E2/M1$ multipole mixing ratios from the ${2}_{x}^{+}[x=2\text{\ensuremath{-}}6]\ensuremath{\rightarrow}{2}_{1}^{+}$ transitions have been examined to identify the lowest mixed-symmetry states in these nuclei. In each nucleus, the mixed-symmetry strength appears to be fragmented between more than one level. The summed $M1$ strength from the ${2}_{x}^{+}$ [$x=2\text{\ensuremath{-}}6$] states to the ${2}_{1}^{+}$ level agrees rather well with neutron-proton interacting boson model predictions in the U(5) or O(6) limits for these Te nuclei.

No neutrinos is good news

A tighter limit on the half-life of a tellurium nucleus for 'neutrinoless double-beta decay' marks progress towards a better understanding of the ever-elusive neutrinos and the measurement of their mass.

Tellurium(II) Dialkanethiolates: np(S)‐σ*(Te−S′) Orbital Interactions Determine the 125Te NMR Chemical Shift, and the Molecular and Crystal Structure

AbstractTellurium(II) dimethanethiolate, Te(SMe)2, and tellurium(II) diethanethiolate, Te(SEt)2, were synthesized by reaction of TeO2 and Te(OiPr)4 with HSMe and HSEt, respectively. In the solid state, Te(SMe)2 exhibits a cis‐conformation of the methyl groups with respect to the TeS2 plane − an unprecedented situation for nonfunctionalized organotrichalcogenides − whereas Te(SEt)2 shows a trans‐conformation. Ab initio calculations performed for Te(SMe)2 and Te(SEt)2 show that the cis‐ and trans‐conformers represent minima on the potential energy surface and are stabilized by intramolecular π‐type n(S)‐σ*(Te−S′) orbital interactions. In the solid state, the molecules of each compound are associated through two centrosymmetric Te2S2 units with two of their neighbors, resulting in tetracoordinate Te atoms with distorted trapezoidal configurations. While the intermolecular Te···S distance increases in the sequence R = Me < Et < iPr < tBu, the length of the covalent Te−S bond decreases in the same order, a result attributed to intermolecular σ‐type np(S)‐σ*(Te−S′) orbital interactions. The 125Te NMR chemical shift of Te(SR)2 largely depends on R (R = Me, Et, iPr, tBu) and shows a nearly linear correlation with the first ionization energy of the corresponding thiol HSR. Ab initio calculations of the 125Te NMR shifts for the model compound Te(SH)2 (C2 symmetry) reveal that it also depends strongly on the HSTeS torsion angle. These results can be explained by a model in which π‐type np(S)‐σ*(Te−S′) and np(Te)‐σ*(S−H) orbital interactions determine the paramagnetic shielding of the tellurium nucleus. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Overcrowded 1,8-diazafluorenylidene-chalcoxanthenes. Introducing nitrogens at the fjord regions of bistricyclic aromatic enes.

The effects of introducing nitrogen atoms in the fjord regions and chalcogen bridges on the conformations of overcrowded bistricyclic aromatic enes (1, X not equal to Y) (BAEs) were studied. 9-(9'H-1',8'-Diazafluoren-9'-ylidene)-9H-thioxanthene (12), 9-(9H-1',8'-diazafluoren-9'-ylidene)-9H-selenoxanthene (13), 9-(9'H-1',8'-diazafluoren-9'-ylidene)-9H-telluroxanthene (14), 9-(9' H-1',8'-fluoren-9-ylidene)-9H-xanthene (15) and 9-(9' H-1',8'-fluoren-9'-ylidene)-9H-fluorene (16) were synthesized by two-fold extrusion coupling reactions of 1,8-diaza-9H-fluoren-9-one (19)/chalcoxanthenthiones (24-27) (or /9H-fluorene-9-thione (30)). The 1',8'-diazafluoren-9-ylidene-chalcoxanthenes (11) were compared with the respective fluoren-9-ylidene-chalcoxanthenes (10). The structures of 12-16 were established by 1H, 13C, 77Se, and 125Te NMR spectroscopies. The crystal and molecular structures of 12-14 were determined by X-ray analysis. The yellow molecules of 12-14 adopted mono-folded conformations with folding dihedrals in the chalocoxanthylidene moieties of 62.7 degrees (12), 62.4 degrees (13) and 59.9 degrees (14). The folding dihedrals in the respective 1',8'-diazafluorenylidene moieties were very small, ca. 2 degrees, compared with 10.2/8.0 degrees in (9'H-fluoren-9'-ylidene)-9H-selenoxanthene (7). A 5 degree pure twist of C9=C9' in 14 is noted. The degrees of overcrowding in the fjord regions of 12-14 (intramolecular non-bonding distances) were relatively small. The degrees of pyramidalization of C9 and C9' were 17.0/3.0 degrees (12), 17.4/2.4 degrees (13) and 2.2/2.2 degrees (14). These high values in 12 and 13 stem from the resistance of the 1.8-diazafluorenylidene moiety to fold and from the limits in the degrees of folding of the thioxanthylidene and selenoxanthylidene moieties (due to shorter S10-C4a/S10-C10a and Se10-C4a/Se10-C10a bonds, as compared with the respective Te-C bonds in 14). The molecules of 15 and 16 adopt twisted conformations, a conclusion drawn from the 1H NMR chemical shifts of the fjord regions protons (H1 and H8) at 8.70 (15) and 9.00 ppm (16) and from their colors and UV/VIS spectra: 15 is purple (lambdamax = 521 nm) and 16 is orange-red. A comparison of the NMR spectra of 11 and 10 (deltadelta = delta(11) -delta(10)) showed substantial downfield shifts of 0.56-0.62 ppm of the fjord regions protons of twisted 15 and 16: deltadelta (C9) were negative (upfield): -4.0 (12), -3.7 (13), -3.4 (14), -7.1 (15), -5.0 ppm (16), while deltadelta (C9') were positive (downfield) = +6.8 (12), +6.5 (13), +5.8 (14), + 11.7 (15), +7.7 ppm (16). In 15, deltadelta (C9) - deltadelta (C9') = + 18.8 ppm, attributed to a push-pull character and significant contributions of zwitterionic structures in the twisted conformation. The 77Se and 125Te NMR signals of 13 and 14 were shifted upfield relative to the respective fluorenylidene-chalcoxanthene derivatives: deltadelta77Se = 17.2 ppm and deltadelta125Te = 22.0 ppm. The presence of the nitrogen atoms (N1' and N8') in 13 and 14 causes shielding of the selenium and tellurium nuclei.

Yrast excitations in A = 126–131 Te nuclei from deep inelastic 130Te+ 64Ni reactions

Thick target γγ coincidence measurements for the system 130Te + 275 MeV 64Ni have been performed using the GASP Ge detector array at Legnaro. For the isotopic assignments of previously unknown γ-ray cascades, prompt γγ coincidences observed between Te and Ni partner products were of vital importance. The results yield much new information about excited states of moderate spins in A = 126–131 tellurium nuclei, especially about yrast excitations of the little studied odd- A isotopes 127Te, 129Te, and 131Te. Level systematics of tellurium nuclei are presented, and both single-particle and collective aspects of the level spectra are discussed.

E2 transition and $$Q_{J^ + } $$ systematics of even mass tellurium nucleisystematics of even mass tellurium nuclei

The yrast spectra withJmaxπ = 6+,B(E2) transition probabilities and\(Q_{J^ + } \) values are calculated for even-even tellurium isotopes by carrying out Hartree-Fock-Bogoliubov (HFB) anstaz employing a pairing-plus-quadrupole-quadrupole effective interaction operating in a reasonably large valence space outside the100Sn core. Our calculations reproduce qualitatively the observed parabolic systematics of the low-lying yrast states as a function of mass number for tellurium isotopes. The results onB(E2) transition probabilities predict a dip in the isotopes114,118,124Te which might be construed to imply different structures for114,118,124Te as compared to their neighbours. Besides this, our results also reveal that both the HFB technique as well as the quadrupole-quadrupole-plus-pairing model of the two body interaction are fairly reliable in this mass region.

High spin states in116Te

The high spin states in116Te were populated in the Ru(19F,p4n) reaction at Elab=90MeV and the subsequent deexcitation was studied using the γ-ray spectroscopic techniques. Ninteen new transitions have been added to extend the level scheme. A ΔI=2 rotational band is identified for the first time in an even-A Tellurium nucleus.

An investigation of iron chromium tellurates by iron-57, tellurium-125 and iodine-129 Mössbauer spectroscopy

The57Fe Mossbauer spectra recorded at 4.2K from the trirutile-type iron chromium tellurates of composition Fe2−xCrxTeO6, where x=0–2, show that the angle θ, which describes the perpendicular orientation of the magnetic moment to the basal plane of the Fe2TeO6 unit cell, is not changed by the incorporation of chromium until x exceeds 1.2 At this critical limit θ begins to rapidly cant to smaller values until, at compositions approaching Cr2TeO6, it approaches a parallel orientation to the basal plane. The125Te and129I Mossbauer spectra recorded from the compound FeCrTeO6 at 77 and 4.2K are consistent with the presence of a supertransferred magnetic hyperfine field at the tellurium nucleus ofca. 76 kG.

Nuclear structure studies with pick-up reactions on even tellurium nuclei: The 120Te(d,t) 119Te and the 120Te(τ, α) 119Te reactions

The level structure of 119Te has been investigated up to an excitation energy of ≈ 1.2 MeV by the (d,t) reaction and up to ≈ 2.3 MeV by the (τ, α) reaction using beams of 17 MeV deuterons and 24 MeV τ-particles. Angular distributions were recorded and analyzed with standard DWBA calculations. Spectroscopic factors were deduced. Anomalous angular distributions and cross sections of some low-lying and weakly excited states were explained using CCBA calculations. A previously known isomeric 11 2 − state has been found to have an excitation energy of 262 keV.

A tellurium-125 and tin-119 Mössbauer and nuclear magnetic resonance study of the group IV organotellurides

The 125Te Mössbauer and nmr spectra of the compounds (R3X)2Te(R = Me, X = C, Si, Ge, and Sn; R = Ph, X = Ge and Sn), R3MTePh (R = Me, X = Si, Ge, and Sn; R = Ph, X = Ge, Sn, Pb), R2Sn(TePh)2 (R = Me and t-Bu), and the cyclic compounds (Me2SnTe)3, (Me2Sn)3Te2, and (t-Bu2SnTe)2 have been measured. The trends in the Mössbauer and nmr data are discussed. The Mössbauer quadrupole splittings increase as the nmr chemical shifts become more positive, corresponding to a decrease in the shielding at the tellurium nucleus. The 119Sn Mössbauer and nmr parameters of the compounds (R3Sn)2E andR3SnEPh (R = Me and Ph), (Me2SnE)3, (Me2Sn)2E2, (t-Bu2SnE)2, and Me2Sn(EPh)2 (E = S, Se, and Te) are discussed. The 119Sn Mössbauer quadrupole splittings are again observed to increase as the nmr chemical shifts become more positive. The 125Te and 119Sn nmr and Mössbauer data provide evidence that there is little transmission of bonding effects through the tin–tellurium bond as the chemical environment about the tin or tellurium is changed.

Effect of chemical structure on the electron density at the tellurium nucleus

This paper reports results of a study in which the Xα-SW method is employed to deduce estimates of the differences in the electron densities at the Te nucleus in some compounds. On the basis of these estimates some assertions are deduced to the calibration problem of the Mossbauer nuclide125Te and to the chemical influence on the IC of the 35.5 keV M1+E2 transition in125Te.

5-125I-iododeoxyuridine as prototype for radionuclide therapy with Auger emitters.

MANY of the physical and biological requirements for treating cancer with internally emitting radionuclides are met by 5-125I-iododeoxyuridine (125IUdR). The decay of 123I is associated with a highly localised deposition of energy1. Cascades of very low energy and thus densely ionising Auger electrons are released. In addition, a charge transfer reaction takes place leaving the resultant tellurium nucleus with a transient mean net charge of +9 (ref. 2). These unique physical characteristics can be used for cell destruction by labelling DNA with 125IUdR, a thymidine analogue. The marked radiotoxicity of 125I incorporated into DNA as 125IUdR has been demonstrated by lethality, mutations and DNA strand breaks in bacteria and bacteriophage3–7, by lethality and chromosome aberrations in mammalian cells cultured in vitro8–10, and by diminished survival of prelabelled tumour cells assayed in vivo11. The intranuclear location is of major importance: 125I located extracellularly9 or bound to cell membranes is much less toxic (unpublished work of R. L. Warters and K. G. Hofer). These findings suggested that 125IUdR might have significant anti-neoplastic activity. We tested this hypothesis in a murine ascites tumour model12,13. In a pilot study using therapeutic doses of 125IUdR, the agent substantially augmented the median and absolute survival of treated animals. The critical factors affecting treatment of a 1-d-old ascites tumour model with 125IUdR are detailed here.

Study of (d, p) reactions on even tellurium nuclei: The 122Te(d, p) 123Te reaction

The energy levels of 123Te have been studied in the 122Te(d, p) 123Te reaction at 7.5 MeV bombarding energy using the MIT multiple-gap magnetic spectrograph. More than one hundred levels were observed up to 5.5 MeV excitation energy. Angular distributions were measured and l-assignments given for 32 of the stronger proton groups. The level scheme was compared to results from IAR and radioactive decay studies. A new 1 2 + level was observed at 600 keV. A DWBA analysis was used to obtain spectroscopic amplitudes for orbits in the 50–82 neutron shell. Following standard prescriptions a comparative analysis of the data from the five reactions A Te(d, p) A + 1 Te, A = 122, 124, 126, 128, 130 was performed and pairing model parameters were extracted. The obtained information indicates that the constant pairing strength approximation is reasonable for the 50–82 neutron orbits in tellurium nuclei.