Sn(20.5) square(3.5)As(22)I(8): a largely disordered cationic clathrate with a new type of superstructure and abnormally low thermal conductivity

Sn(20.5)As(22)I(8), a new cationic clathrate, has been prepared by using an ampoule technique. According to the X-ray powder diffraction data, it crystallizes in the face-centered cubic space group F23 or Fm(-)3 with a unit-cell parameter of a=22.1837(4) A. Single-crystal X-ray data allowed solution of the crystal structure in the subcell with a unit-cell parameter of a(0)=11.092(1) A and the space group Pm(-)3n (R=5.7 %). Sn(20.5)As(22)I(8) (or Sn(20.5) square(3.5)As(22)I(8), accounting for the vacancies in the framework) possesses the clathrate-I type crystal structure, with iodine atoms occupying the cages of the cationic framework composed of tin and arsenic atoms. The crystal structure is strongly disordered. The main features are a random distribution of vacancies, and shifts of the tin and arsenic atoms away from their ideal positions. The coordination of the tin atoms has been confirmed by using (119)Sn M?ssbauer spectroscopy. Electron diffraction and high-resolution electron microscopy (HREM) analyses have confirmed the presence of the superstructure ordering, which results in a doubling of the unit-cell parameter and a change of the space group from Pm(-)3n to either F23 or Fm(-)3. Analysis of the crystal structure has led to the construction of four ordering models for the superstructure, which have been corroborated by HREM, and has also led to the identification of disordered regions originating from overlap of the different types of ordered domains. Sn(20.5)As(22)I(8) is a diamagnetic semiconductor with an estimated band gap of 0.45 eV; it displays abnormally low thermal conductivity, with the room temperature value being just 0.5 W m(-1) K(-1).     

Distribution of phosphorus and arsenic atoms in the solid solution Sn24AsxP19.3-xI8 with the structure of clathrate-I

The solid solution Sn₂₄As _x P_19.3-x I₈ in the range of compositions x from 0 to 16 was synthesized. The crystal structure was refined for seven compositions of the solid solution at —100 °C. All samples crystallize in the cubic space group Pm3 n with the unit cell parameters a = 10.9358(2)—11.1495(2) ? and belong to the clathrate-I structure type. The distribution of the phosphorus and arsenic atoms over two independent crystallographic positions within the clathrate framework was analyzed. The difference in the structure of the substituted clathrates with the cationic and anionic clathrate frameworks is considered.     

Gradient-corrected density-functional potential with correct asymptotic behavior: application to interconfigurational energies in transition-metal atoms

Based upon the optimized effective potential with the self-interaction correction, we present in this paper an alternative gradient-corrected density-functional approximation with the proper long-range behavior of the effective potential. As applied to the study of the interconfigurational energies of the whole transition-metal atoms, the present combination of the gradient-corrected contribution and the modified optimized effective potential lead the s ionization to the excellent agreement with the experiment. The calculated d ionizations and s-d transition energies are also discussed.     

Unusually high chemical compressibility of normally rigid type-I clathrate framework: synthesis and structural study of Sn(24)P(19.3)Br(x)I(8)(-)(x) solid solution, the prospective thermoelectric material

A novel tin phosphide bromide, Sn(24)P(19.3(2))Br(8), and Sn(24)P(19.3(2))Br(x)()I(8)(-)(x) (x = 0-8) solid solution have been prepared and structurally characterized. All compounds crystallize with the type-I clathrate structure in the cubic space group Pmn (No. 223). The clathrate framework of the title solid solution shows a remarkable chemical compressibility: the unit cell parameter drops from 10.954(1) to 10.820(1) A on going from x = 0 to x = 8, a feature that has never been observed for normally rigid clathrate frameworks. The chemical compressibility as well as non-Vegard dependence of the unit cell parameter upon the bromine content is attributed to the nonuniform distribution of the guest halogen atoms in the polyhedral cavities of the clathrate framework. The temperature-dependent structural study performed on Sn(24)P(19.3(2))Br(8) has shown that, in contrast to the chemical compressibility, the thermal compressibility (linear contraction) of the phase is similar to that observed for the Group 14 anionic clathrates. The tin phosphide bromide does not undergo phase transition down to 90 K, and the atomic displacement parameters for all atoms decrease linearly upon lowering the temperature. These linear dependencies have been used to assess such physical constants as Debye temperature, 220 K, and the lattice part of thermal conductivity, 0.7 W/(m K). Principal differences between the title compounds and the group 14 anionic clathrates are highlighted, and the prospects of creating new thermoelectric materials based on cationic clathrates are briefly discussed.     

The layered thiostannate (dienH2)Cu2Sn2S6: a photoconductive inorganic-organic hybrid compound

The new inorganic-organic hybrid compound (dienH2)Cu2Sn2S6 (dien = diethylenetriamine) was synthesized under solvothermal conditions. It crystallizes in the tetragonal space group I4m2 with a = 7.8793(3) A, c = 24.9955(15) A, and V = 1551.80(13) A(3). The structure consists of anionic [Cu2Sn2S6](2-) layers extending in the (001) plane and protonated amine molecules as charge compensating ions sandwiched between the layers. The layered [Cu2Sn2S6](2-) anion is composed of a single layer of edge-sharing CuS4 tetrahedra which is joined above and below to straight chains constructed by corner-sharing SnS4 tetrahedra. The material is a semiconductor with an optical band gap of 1.51 eV. More interestingly, preliminary results demonstrate that the compound exhibits photoconductive properties with an increase of the conductivity by a factor of 3 when irradiated with UV light. Upon heating in an inert atmosphere the compound starts to decompose at about 256 degrees C.     

Copper(I) hexafluoroantimonate - an example of a compound with Cu in a solely fluorine environment

Yellow-orange single crystals of CuSbF₆, were prepared by reacting Cu wire (∼10 mmol) with SbF₅ (∼3 mmol) in liquid anhydrous hydrogen fluoride (aHF) and by reduction of Cu(SbF₆)₂ with Cu metal in aHF. CuSbF₆ crystallizes rhombohedral at 296 K with the LiSbF₆ structure type, with a = 530.4(4) pm, c = 1453(1) pm and Z = 3, space group R (no. 148). The structure is dominated by isolated layers of regular [SbF₆]⁻ octahedra and Cu⁺ cations.An attempt to prepare CuF by reaction between CuSbF₆ and CsF in aHF at ∼190 K failed. Instead of CuF, a mixture of Cu and CuF₂ was obtained.     

Mixed-valence Cu(II)Cu(I)15I17 cluster builds up a 3D metal-organic framework with paramagnetic and thermochromic characteristics

Four cubane-like Cu4I4 units are assembled around an iodine atom to form the giant, mixed-valent Cu(II)Cu(I)15I17 cluster. The Cu(II)Cu(I)15I17 cluster and a bipyrazole linker form a 3D open framework with paramagnetic and thermochromic properties. This paper also touches on the resemblance of this cluster to the self-similar object of a Sierpinski tetrahedron.     

SrZn11: a new binary compound with the BaCd11 structure

Single crystals of strontium undecazinc, SrZn₁₁, were obtained when decomposing SrZn₂ under conditions of high pressure and high temperature. The new binary Sr–Zn compound crystallizes in the space group I4₁/amd (BaCd₁₁ structure type) with one Sr position (m2) and three Zn sites (m2, .2/m., 1). The structure is described in terms of all‐face‐capped Zn₈ tetrahedra as the central building unit, defined by the Zn atoms on .2/m. and 1. The building units are condensed into chains by the central tetrahedra sharing edges, and the chains are interconnected by shared capping atoms. The resulting three‐dimensional framework of Zn atoms yields channels that are occupied by Sr and Zn atoms on the high‐symmetry m2 positions.     

[Cu2I2(C8H6N2)]∞晶体的水相合成与表征

近年来,d10金属配位聚合物的合成、结构和性质的研究引起了人们广泛的兴趣[1-3],CuXL(X＝Cl、Br和I,L＝含氮配体)配合物由于其结构的多样性和独特的发光性质而成为活跃的研究领域[1-10].     

H3N(CH2)7NH3]8(CH3NH3)2Sn(IV)Sn(II)12I46- a mixed-valent hybrid compound with a uniquely templated defect-perovskite structure

The incorporation of H(3)N(CH(2))(7)NH(3) with CH(3)NH(3)SnI(3) resulted in the formation of a mixed-valent and semiconducting (Eg = 0.84 eV) organic-based perovskite, [H(3)N(CH(2))(7)NH(3)](8)(CH(3)NH(3))(2)Sn(iv)Sn(ii)(12)I(46), with a unique 3D defect-perovskite structure with ordered vacancies at the Sn and I sites.     

ChemInform Abstract: Zintl Phases in Alkali-Metal-Tin Systems: K8Sn25 with Condensed Pentagonal Dodecahedra of Tin. Two A8Sn44 Phases with a Defect Clathrate Structure.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

N4H9Cu7S4: a hydrazinium-based salt with a layered Cu7S4- framework

Crystals of a hydrazinium-based copper(I) sulfide salt, N4H9Cu7S4 (1), have been isolated by an ambient temperature solution-based process. In contrast to previously reported hydrazinium salts of main-group metal chalcogenides, which consist of isolated metal chalcogenide anions, and ACu7S4 (A = NH4+, Rb+, Tl+, K+), which contains a more three-dimensional Cu7S4- framework with partial Cu-site occupancy, the structure of 1 [P21, a = 6.8621(4) A, b = 7.9851(4) A, c = 10.0983(5) A, beta = 99.360(1) degrees , Z = 2] is composed of extended two-dimensional Cu7S4- slabs with full Cu-site occupancy. The Cu7S4- slabs are separated by a mixture of hydrazinium and hydrazine moieties. Thermal decomposition of 1 into copper(I) sulfide proceeds at a significantly lower temperature than that observed for analogous hydrazinium salts of previously considered metal chalcogenides, completing the transition at temperatures as low as 120 degrees C. Solutions of 1 may be used in the solution deposition of a range of Cu-containing chalcogenide films.     

Covalent surface modification of a metal-organic framework: selective surface engineering via Cu(I)-catalyzed Huisgen cycloaddition

A Zn-cornered, mixed-ligand, metal-organic framework (MOF) bearing TMS-protected acetylenes has been constructed and its surface decorated with organic molecules via'click chemistry', in a demonstration of selective post-synthesis functionalization.     

Polymerisation of pentadienyl compounds in the presence of transition-metal compounds: the polymorphic compound deca-1,3,7,9-tetraenediiron hexacarbonyl

The reaction between Fe(CO)₅ and penta-1,4-dien-3-ol gives two forms of di(pentadienyliron tricarbonyl).     

Ba11Cd8Bi14: bismuth zigzag chains in a ternary alkaline-earth transition-metal Zintl phase

A new transition-metal-containing Zintl phase, Ba11Cd8Bi14, has been synthesized by a Cd-flux reaction, and its structure has been determined by a single-crystal X-ray diffraction. Ba11Cd8Bi14 crystallizes in the monoclinic space group C2/m (No. 12, Z = 2) with a = 28.193(8) A, b = 4.8932(14) A, c = 16.823(5) A, and beta = 90.836(4) degrees , taken at -150 degrees C (R1 = 0.0407, wR2 = 0.1016). The structure can be described as being built of complex polyanionic [Cd8Bi14]22- layers running along the b axis, which are separated by the Ba2+ cations. An interesting feature of these layers is that they are composed of novel centrosymmetric chains of corner- and edge-shared CdBi4 tetrahedra, interconnected through exo-Bi-Bi bonds. These bonds connect terminal Bi atoms from adjacent chains in such a way that infinite zigzag chains of bismuth parallel to the same direction are formed. Electronic band structure calculations performed using the TB-LMTO-ASA method show a very small band gap, suggesting a narrow-gap semiconducting or poor metallic behavior for Ba11Cd8Bi14. The crystal orbital Hamilton population (COHP) analysis on the homo- and heteroatomic interactions in this structure is reported as well.