Christoph L. Teske

Darstellung, Eigenschaften, röntgenographische und spektroskopische Untersuchung von Tl4Nb2S11 und Tl4Ta2S11

Die neuen ternaren Polysulfide Tl4Nb2S11 und Tl4Ta2S11 wurden durch Reaktion der Ubergangsmetalle in Thallium-Polysulfidschmelzen synthetisiert. Tl4M2S11 kristallisiert isotyp mit K4Nb2S8.9Se2.1 in der triklinen Raumgruppe P 1 mit a = 7,806(2) A, b = 8,866(2) A, c = 13,121(3) A, α = 72,72(2)°, β = 88,80(3)° und γ = 85,86(2)° fur M = Nb und a = 7,837(1) A, b = 8,902(1) A, c = 13,176(1) A, α = 72,69(1)°, β = 88,74(1)° und γ = 85,67(1)° fur M = Ta. Die interatomaren Abstande und Winkel in den [M2S11]4– Anionen weisen geringfugige Unterschiede zu den homologen Alkalimetallverbindungen auf. Allerdings werden signifikante Unterschiede in der Form der TlSx- im Vergleich zu den ASx-Polyedern (A = K, Rb, Cs) gefunden. Die Titelverbindungen schmelzen kongruent bei 732 K (Tl4Nb2S11) bzw. 729 K (Tl4Ta2S11). Aus den UV/Vis-Spektren wurden die optischen Bandlucken fur Tl4Nb2S11 zu 1,26 eV und fur Tl4Ta2S11 zu 1,80 eV abgeschatzt. On Polychalcogenides of Thallium with M2Q11 Groups as a Structural Building Block. I Preparation, Properties, X-ray Diffractometry, and Spectroscopic Investigations of Tl4Nb2S11 and Tl4Ta2S11 The new ternary compounds Tl4Nb2S11 and Tl4Ta2S11 were prepared using Thallium polysulfide melts. Tl4M2S11 crystallises isotypically to K4Nb2S8.9Se2.1 in the triclinic space group P 1 with a = 7.806(2) A, b = 8.866(2) A, c = 13.121(3) A, α = 72.72(2)°, β = 88.80(3)°, and γ = 85.86(2)° for M = Nb and a = 7.837(1) A, b = 8.902(1) A, c = 13.176(1) A, α = 72.69(1)°, β = 88.74(1)°, and γ = 85.67(1)° for M = Ta. The interatomic distances as well as angles within the [M2S11]4– anions are similar to those of the previously reported data for analogous alkali metal polysulfides. Significant differences between Tl4M2S11 and A4M2S11 (A = K, Rb, Cs) are obvious for the shape of the polyhedra around the electropositive elements. The two title compounds melt congruently at 732 K (M = Nb) and 729 K (M = Ta). The optical band gaps were estimated as 1.26 eV for Tl4Nb2S11 and as 1.80 eV for the Tantalum compound.

Size-dependent properties ofTl2Sestudied by NMR spectroscopy

We report on size-dependent properties of dithallium selenide, Tl2Se. We have carried out a comparative nuclear magnetic resonance (NMR) study of Tl2Se nanorods and bulk samples, measuring NMR spectra and spin-lattice relaxation rate of 203Tl and 205Tl isotopes. Though bulk Tl2Se was reported to be a metal, the Korringa-like spin-lattice relaxation behavior is observed only at low temperatures and is transformed to an activation regime above ~200 K. This finding is interpreted assuming a two-band model in the semimetallic compound. Our measurements show significant difference in the Knight shift and indirect nuclear exchange coupling for the bulk and nanorod Tl2Se samples, reflecting noticeable distinction in their electronic structure. At that, Tl2Se nanorods are semiconductors and exhibit a characteristic activation behavior in the spin-lattice relaxation rate due to the thermal excitation of carriers to the conduction band. The obtained size dependence of the Tl2Se properties is interpreted in terms of the semimetal-semiconductor transformation due to the quantum confinement.

On Polychalcogenides of Thallium with M2 Q11 Groups as a Structural Building Block. II. Tl4Ta2Se11: Synthesis, Crystal Structure, Properties and Spectroscopic Investigations of the First Polyselenide being Composed of a Discrete [Ta2Se11]4— Anion

The new ternary compound Tl4Ta2Se11 was prepared in a melt of thallium polyselenides applying elemental tantalum. It crystallises in the triclinic space group P1¯ with a = 7.996(1) A, b = 9.866(1) A, c = 13.668(2) A, α = 73.03(1)°, β = 89.21(2)° and γ = 85.72(1)°. Tl4Ta2Se11 is the first polyselenide with discrete complex [M2Se11]4— anions. Every Ta atom is in a sevenfold environment of Se atoms to form a distorted pentagonal bi-pyramid. The two TaSe7 polyhedra have a face in common thus yielding the [Ta2Se11]4— unit. In the structure, the anions are well separated by the Tl1+ cations. An assignment of the different vibration modes in the IR and Raman spectra is given based on density functional calculations.

Nuclear spin diffusion in the semiconductor TlTaS 3

We report on a

Preparation, Crystal Structure, Physical Properties, and Electronic Band Structure of TlTaS3Professor Welf Bronger zum 70. Geburtstag gewidmet

^{203}\mathrm{Tl}

Preparation, Crystal Structure, Properties, and Electronic Band Structure of TlTaSe3

and

Preparation of Tl-1223 Bulk Samples on Large Scale

^{205}\mathrm{Tl}

On Crystal Structure Investigations of α- and β-Ammoniumdithiocarbamate NH4CS2NH2 and the Role of Hydrogen Bonding

nuclear magnetic resonance study of the chain ternary semiconductor

On Ammonium-tetrakis(dithiocarbamato)-bismuth(III)-monohydrate and Tris(dithiocarbamato)-bismuth(III)†

{\mathrm{TlTaS}}_{3}

Die Kristallstruktur von Ytterbiumdisulfid: YbS2 / The Crystal Structure of Ytterbiumdisulfide: YbS2

. We show that spin-lattice relaxation in this compound is driven by two contributions, namely, by interactions of nuclear spins with thermally activated carriers and with localized electron spins. The latter mechanism dominates at lower temperature; at that, our measurements provide striking manifestation of the spin-diffusion-limited relaxation regime. The experimental data obtained allow us to estimate the spin diffusion coefficient.