New bisdithiolene metal complex of the 2-thioxo-1,3-dithiole-4,5-dithiolato(dmit) ligand. Preparation,structure and physical properties

The complex HMEDA[Ni(dmit)₂]₂I (HMEDA=Hexamethylethylenediammonium) has been prepared. A single X-ray crystal structure analysis reveals that there are short S⋯S contacts between Ni(dmit)₂ dimmers. The monoclinic system, space group p2/n, has cell dimensions: a=11.710(3) Å, b=22.559(5) Å, c=7.374(2) Å, β=93.000(3)⁰, V=1945.3(8) ų, z=4. Full-matrix least-squares refinement, based on 2989 reflections converged at R=0.0686. The conductivity of this salt at room temperature is 0.1 S cm⁻¹ and it shows semiconducting behavior from 20 to 300 K.     

Synthesis,electrical properties and crystal structure of a new et-based charge-transfer salt containing binuclear polychloride complex anion

A new charge-transfer salt containing hexachlorodicuprate (II) binuclear polychloride complex counter anions, ET₂Cu₂Cl₆ (ET = BEDT-TTF = bis (ethylenedithio)-tetrathiafulvalene), was prepared. The room-temperature d.c. conductivity and relative resistance temperature dependence of the salt from room temperature down to 77 K along the longest crystal growth direction are reported. The crystal structure is determined by the X-ray diffraction method at room temperature. It belongs to the triclinicpl space group with crystallographic parameters of a = 11.379(4), b= 16.353(4), c = 9.054(4) A, α = 90.33(3), β= 100.69(3), γ= 100.06(2) °, V= 1628(1) A³, Z = 2, d_c = 2.261 g cm⁻³, λ (Mo Kα) = 0.710 69 A, μ = 28.45 cm⁻¹, F₀₀₀ = 1104.00 and final R = 0.043, R_w = 0.057 for 2331 observed reflections. The structure consists of isolated ET stacks and the binuclear polychloride complex dianion (Cu₂Cl₆)²⁻ sheets. In the donor stack, significantly short S···S contacts are observed.     

Synthesis,crystal structure and electrical conductivity of [bmim][Ni(dmit)2]3 (bmim = 1-butyl-3-methylimidazolium,dmit = 1,3-dithiol-2-thione-4,5-dithiolate)

A new complex [bmim][Ni(dmit)₂]₃ has been prepared, and its crystal structure and electrical conductivity where determined and measured. Crystallographic parameters for C₂₆H₁₅N₂S₃₀Ni₃: triclinic system; space group: P-1; a=12.760(3), b=19.441(4), c=11.670(2) Å; α=102.00(3), β=117.10(3), γ=95.06(3)°; Z=2, R=0.0579 (I>2σ(I)). The conductivity of this salt at room temperature is 1.7×10⁻² S cm⁻¹ and it shows semiconduction in the temperature range of 110–290 K.     

Crystal and electronic structures and physical properties of two semiconductors: Pb4Sb6Se13 and Pb6Sb6Se17

The title compounds were synthesized by directly reacting the elements in stoichiometric ratios at elevated temperatures. Their crystal structures were determined by single crystal X-ray diffraction. Pb₄Sb₆Se₁₃ crystallizes in the monoclinic space group I2/m with lattice dimensions of a=24.591(1) Å, b=4.0910(2) Å, c=25.212(1) Å, β=93.943(1)°, V=2530.3(2) Å³ (Z=4), while Pb₆Sb₆Se₁₇ crystallizes in the orthorhombic space group P2₁2₁2 with lattice dimensions of a=15.872(4) Å, b=24.061(7) Å, c=4.1382(9) Å, V=1580.4(7) Å³ (Z=2). Electronic structure calculations predicted semiconducting behavior. Temperature dependent electrical conductivity measurements verified this prediction for Pb₄Sb₆Se₁₃.     

Preparation,crystal structures and electrical conducting properties of new charge-transfer salts: (ET)2·SO3CF3 and (ET)·ClO4

Two new charge-transfer (CT) salts: (ET)₂·SO₃CF₃ and (ET)·ClO₄ were prepared by chemical oxidation of ET with AgSO₃CF₃ and AgClO₄, respectively. Their crystal structures were determined: monoclinic system, Cc, a=35.239(7) Å, b=6.5440(13) Å, c=14.646(3) Å, β=110.26(3)°, V=3168.5(11) Å³ for (ET)₂·SO₃CF₃; monoclinic system, C2/c, a=15.981(3) Å, b=10.627(2) Å, c=11.495(2) Å, β=120.61(3)°, V=1680.2(6) Å³ for (ET)·ClO₄. Electrical conductivity measurements indicate that (ET)₂·SO₃CF₃ shows semi-conducting behaviour with room temperature conductivity of 0.29 S cm⁻¹, while (ET)·ClO₄ is an insulator.     

Crystal and electronic structures of the radical cation salt based on EDT-TTF and the photochromic nitroprusside anion, (EDT-TTF)3[Fe(CN)5NO]

A single crystal X-ray diffraction (XRD) study of the radical cation salt (EDT-TTF)₃[Fe(CN)₅NO] has been carried out (a=6.623(3), b=10.487(2), c=15.951(1) Å, α=109.19(1), β=96.30(2), γ=99.15(3)°, V=1017.3(5) Å³, space group P1, Z=1). The crystals have a layered structure with the distinctive feature of the presence of alternating EDT-TTF dimers and monomers in the radical cation stacks. Both the structural features and the calculated HOMO⋯HOMO interaction energies suggest that the strong intradimer interaction is responsible for the charge separation and the semiconducting properties of the salt.     

Radical cation salts of bis (ethylenediseleno) tetrathiafulvalene with halide mercurate anions

Four bis(ethylenediseleno) tetrathiafulvalene (BEDSe-TTF)-based salts, (BEDSe-TTF)₂Hg₂X₂ (X=I. Br), (BEDSe-TTF)₄Hg₃Br₈ · C₂H₃Cl₃ and (BEDSe-TTF)₄Hg₃Br₄ · 1.5C₂H₃Cl₃, have been prepared by electrocrystallization. Two of them. (BEDSe-TTF)₂Hg₂X₆, have been characterized by X-ray crystallography. The triclinic (space group Pī) room-temperature lattice parameters when X=I are: a = 6.798(4),b = 10.728(7), c 15.905(9) Å, α=106.33(6)°, ß=99.78(4)°, γ-92.97(5), V = 1090(1) ų. When X =Br the parameters are: a=6.665(3), b= 10.314(5), c=15.720(7) Å, α-105.70(4)°, ß=99.65(4)°, γ=93.79(4)°, V = 1018(1) ų. At room temperature, (BEDSe-TTF)₄Hg₃Br₈ · C₂H₃Cl₃ is metallic and the others are semiconductors.     

High-temperature thermoelectric properties of Sr2RuYO6 and Sr2RuErO6 double perovskites influenced by structure and microstructure

The high-temperature thermoelectric properties of Sr₂RuYO₆ and Sr₂RuErO₆ double perovskites were evaluated and reported for the first time. These compounds show high Seebeck coefficients not only at room temperature, but also at high temperature (for Sr₂RuYO₆, S_RT ≈ ?475 μV K^?1 and S_1200K ≈ ?250 μV K^?1; Sr₂RuErO₆, S_RT ≈ ?400 μV K^?1 and S_1200K ≈ ?250 μV K^?1). The n-type semiconducting behaviour dominates the resistivity values. Both compounds crystallize in a monoclinic unit cell (space group P2₁/n). The lattice parameters are a = 5.7761(2), b = 5.7804(1), c = 8.1689(1), α = γ = 90° and β = 90.2087(8)° for the Sr₂RuYO₆, and a = 5.7760(1), b = 5.7722(0), c = 8.1544(4), α = γ = 90° and β = 90.2099(7)° for Sr₂RuErO₆. The unit cell can be described approximately as √2a_p × √2a_p × 2a_p, where a_p is the unit cell parameter of the ideal cubic perovskite structure. High-resolution transmission electron microscopy shows an interesting three-dimensional micro-twin-domain texture where the c axis is placed in the three space directions. Structural transitions at high temperatures (T_t(Sr₂RuYO₆) ≈920 K and T_t(Sr₂RuErO₆) ≈890 K) are observed by specific heat measurement in both compounds, which are found to have a strong influence on the Seebeck coefficient and electrical conductivity.     

Crystal structure of the new ternary indide CePt2In2 and the isostructural compounds RPt2In2 (R=La,Pr, Nd)

The title compounds have been synthesized by arc melting of the elemental components and subsequent annealing at 870 K. The crystal structure of CePt₂In₂ was determined from single-crystal X-ray data (R=0.0437 for 1439 |F| values and 62 variables). It represents a new structure type of intermetallic compounds: P2₁/m, mP20, a=10.189(6), b=4.477(4), c=10.226(6) Å, β=117.00(5)°, V=416.1(1) ų, Z=4. Isostructural compounds have been found also for La, Pr, and Nd.     

The Crystal Structure and Phase Transition of Hf2Pt3

The structure of Hf₂Pt₃ has been re-investigated using transmission electron microscopy and Rietveld refinement of neutron powder diffraction data at temperatures up to 1500 °C. This compound does not belong to the MoSi₂ structure type as previously reported, but instead is isostructural with Ti₂Pd₃ and the low-temperature form of Ti₂Ni₃. The crystal structure is orthorhombic (pseudo-tetragonal), Cmcm, Z = 4, with a = 14.653(1) Å, b = 4.8741(3) Å, and c = 4.8671(3) Å at room temperature. The b/c ratio decreases from 1.0014(2) at room temperature to 1.0005(3) at 1500 °C, but the material does not transform to the high-temperature form of Ti₂Ni₃ (I4/mmm) under the conditions studied. The electron diffraction data indicate multiple stacking faults as well as short-range order. On heating above 1630 °C there is a phase transition to a B2-related structure with a ≈ 3.315(1) Å at 1659 °C.     

Neutron structural and vibrational studies of dipotassium selenate tellurate

At room temperature the potassium selenate tellurate K₂SeO₄·Te(OH)₆ (KSeTe) was prepared from water solution of H₆TeO₆ and K₂SeO₄. Its structure has been determined from single crystal using neutron diffraction data. KSeTe is monoclinic with C2/c space group. The unit cell parameters are: a = 11.572(9) Å, b = 6.437(7) Å, c = 13.938(1) Å, β = 106.07(7)°, V = 997.7(1) Å³ and Z = 4. The main feature of this structure is the presence of two different and independent anions (TeO₆⁶⁻ and SeO₄²⁻) in the same unit cell. The structure is built by layers of TeO₆ octahedra altering with planes of SeO₄ tetrahedra linked by a network of hydrogen bonds performed by protons belonging to the OH hydroxide groups. DSC measurements indicate that the crystals of K₂SeO₄·Te(OH)₆ undergo three endothermal peaks at 433, 480 and 495 K.Raman scattering measurements on KSeTe material taken between 300 and 620 K are reported in this paper. The spectra indicate clearly these phase transitions.     

A new phase in stoichiometric Cu6Sn5

The intermetallic compound Cu₆Sn₅ is a significant microstructural feature of many electronic devices where it is present at the solder–substrate interfaces. The time- and temperature-dependent thermomechanical properties of Cu₆Sn₅ are dependent on the nature and stability of its crystal structure, which has been shown to exist in at least four variants (η, η′, η⁶ and η⁸). This research details an additional newly identified monoclinic-based structure in directly alloyed stoichiometric Cu₆Sn₅ using variable-temperature synchrotron X-ray diffraction (XRD) and transmission electron microscopy. The phase is associated with a departure from the equilibrium temperature of the polymorphic monoclinic–hexagonal transformation temperature. The new monoclinic phase can be treated as a modulation of four η⁸-Cu₅Sn₄ unit cells plus one η′-Cu₆Sn₅ unit cell. It has been labeled as η⁴⁺¹ and has cell parameters of a = 92.241 Å, b = 7.311 Å, c = 9.880 Å and β = 118.95° determined from electron diffraction patterns. The XRD results could be fitted well to a Rietveld refinement using the new crystal parameters.     

Intermolecular interactions in the structure of new molecular semiconductor [Pd(dddt)2]2CF3SO3

An X-ray structural investigation of a new molecular semiconductor, [Pd(dddt)₂]₂CF₃SO₃ (1), where dddt²⁻ is 5,6-dihydro-1,4-dithiin-2,3-dithiolate, is made. Crystal data of 1:a = 6.521(7) Å, b = 8.354(4) Å, c = 16.113(6) Å, α = 87.12(4)°, β = 85.51(6)°, γ = 67.94(7)°, V = 811(1) ų, triclinic, space group P. Crystal structure 1 is characterized by layers of [Pd(dddt)₂]^1/2+ radical cations, with [CF₃SO₃]⁻ anions located between them. In these layers, [Pd(dddt)²]^1/2+ cations form dimers with strongly shortened intermolecular contacts Pd…Pd 3.031 (2) Å. The [CF₃SO₃]⁻ anion in the structure of 1 is disordered.     

Thermoelectric properties of the new tellurides SrSc2Te4 and BaSc2Te4 in comparison to BaY2Te4

The two new ternary scandium tellurides SrSc₂Te₄ and BaSc₂Te₄ were prepared by heating the elements at temperatures between 800 °C and 900 °C under vacuum. Both compounds crystallize in the CaFe₂O₄ type, space group Pnma, Z = 4, with lattice dimensions of a = 13.1795(17) Å, b = 4.2323(7) Å, c = 15.367(2) Å, V = 857.2(2) Å³ for SrSc₂Te₄, and a = 13.292(2) Å, b = 4.2694(7) Å, c = 15.523(3) Å, V = 880.9(2) Å³ for BaSc₂Te₄. The structures comprise a three-dimensional network of edge- and corner-sharing ScTe₆ octahedra. The Sr and Ba cations are located in linear channels, surrounded by eight Te atoms forming bicapped trigonal prisms. SrSc₂Te₄ and BaSc₂Te₄ are electron-precise materials exhibiting common oxidation states, Sr²⁺, Ba²⁺, Sc³⁺, and Te²⁻. We calculated the band gaps to be 0.1 eV for SrSc₂Te₄ and 0.2 eV for BaSc₂Te₄. At room temperature, both materials exhibit a high Seebeck coefficient and low electrical conductivity.     

Structural and magnetic properties of UFe6Ga6

UFe₆Ga₆ polycrystalline samples were prepared by arc-melting, and single crystals were grown by the Czochralski method. This compound crystallizes in the orthorhombic ScFe₆Ga₆-type structure (space group Immm, a=5.0560(4), b=8.5484(7) and c=8.6914(7) Å), an ordered variant of the ThMn₁₂-type structure. A ferromagnetic-type transition at T_C=530(5) K is seen in the magnetization and A.C.-susceptibility measurements, and no other magnetic anomaly is observed down to 5 K. Single crystal magnetization measurements along the three different crystallographic axes indicated a as the easy direction, with a spontaneous magnetization M_S=12.3 μ_B/f.u. at 5 K. The analysis of the ⁵⁷Fe Mössbauer spectroscopy data indicated magnetic hyperfine fields, B_hf, significantly lower on 4f sites than on 8k sites, in agreement with the trend already observed on UFe_xAl_12−x, where the average B_hf were found to increase with the iron–iron interatomic distances.     

Two conductive phases of 1,3-dimethylimidazolium-(TCNQ)2 complex salt

Two conductive phases were found by crystallization of the complex ion-radical salt of the 1,3-dimethylimidazolium 7,7′,8,8′-tetracyano1,4-quinodimethane (TCNQ) under different conditions: (i) bulk crystallization from the acetonitrile solution and (ii) crystallization on a glass substrate giving rise to an interconnected fibrous crystal conductive network (σ = 1.7 mS ⁻¹). The electrical conductivity of the latter phase is more than four orders of magnitude higher than that of the former phase. The crystal lattices of both phases are different. The first phase is triclinia (P1) with cell parameters a = 7.811 Å, b = 13.378 Å, c = 7.276 Å, α = 93.152 °, β= 113.739 °, γ = 106.068 °. Indexing of the X-ray diffraction patterns recorded with samples of the latter phase gives a = 13.65 Å, b = 12.70 Å, c = 3.80 Å, γ = 108.3 °; α and β could not be determined.     

The spectroelectrochemical, magnetic, and structural characterization of reduced hexaazatriphenylenehexacarbonitrile, HAT(CN)6

The cyanoazacarbon, hexaazatriphenylenehexacarbonitrile, or HAT(CN)₆, is readily reduced and the spectroelectrochemical properties associated with the multiple reductions are described. The singly reduced radical monoanion forms stable salts and we report the crystal structure and magnetic properties for the tetrabutylammonium salt. [Tetra-n-butylammonium] [HAT(CN)₆] behaves ferromagnetically below 3 K and follows Curie Law behavior at higher temperatures after correction for Pauli-type susceptibility. The room temperature conductivity of the powdered salt is 3.8 × 10⁻⁸ S/cm. The crystal structure shows closely bound pairs of radical anions with slip-stacking of these pairs to form a staircase, features that elucidate the observed properties. Thin films of HAT(CN)₆ were found to support negative charge transport by electron time-of-flight measurements, yielding electron mobilities of 10⁻⁴ cm²/Vs at room temperature.     

Nd2Ni2MgH8 hydride: Synthesis,structure and magnetic properties

Hydrogen interaction with intermetallic compound Nd₂Ni₂Mg crystallizing in the tetragonal Mo₂FeB₂ type of structure leads to the formation of hydride/deuteride containing 7.4–8 H(D)/f.u. Hydrogen absorption is accompanied by a monoclinic deformation of the unit cell with the crystal structure data refined from Synchrotron XRD (Sp. gr. P2₁/c; a = 11.60733(5) Å; b = 7.66057(3) Å; c = 11.78743(5) Å, β = 92.4126(4)°, V = 1047.194(8) ų) and high resolution powder XRD data. The formed interstitial hydride disproportionates during heating forming NdH₂. Nd₂Ni₂Mg is an antiferromagnet with the Néel temperature T_N ≈ 19 K. Presence of another magnetic phase transition at 14 K together with two metamagnetic transitions indicates a complicated magnetic phase diagram. The hydrogenation reduces T_N to 1.0 K.     

Synthesis,crystal structure and thermal behavior of Na4[B10O16(OH)2]·4H2O

New hydrated sodium borate Na₄[B₁₀O₁₆(OH)₂]·4H₂O has been synthesized under mild hydrothermal conditions at 170 °C. The structure was determined by single-crystal X-ray diffraction and further characterized by FT-IR, Raman spectra and DTA-TG. It crystallizes in the monoclinic space group Pc with a unit cell of dimension a = 11.323(2) Å, b = 6.5621(14) Å, c = 12.244(3) Å, α = 90°, β = 91.050(3)°, γ = 90°, V = 909.7(3) Å³, Z = 2. The crystal structure of Na₄[B₁₀O₁₆(OH)₂]·4H₂O consists of Na–O polyhedra and [B₁₀O₁₆(OH)₂]⁴⁻ polyborate anions. Dehydration of this compound occurs in three steps and leads to an amorphous phase which undergoes crystallization.