Ba3.5Cu7.55In1.15Se9: A Wide-Bandgap Copper Indium Selenide Reveals Strong Luminescence and Third-Harmonic Generation.

A new copper indium selenide, Ba3.5Cu7.55In1.15Se9, was synthesized by the KBr flux reaction at 800 °C. The compound crystallizes with orthorhombic Pnma, a = 46.1700(12) Å, b = 4.26710(10) Å, c = 19.8125(5) Å, and Z = 8. The structural framework mainly consists of four sites of cubane-type defective M4Se3 (M = Cu, Cu/In) units with disordered Cu+/In3+ ions present at the part corner of each unit. The single crystal emits intense photoluminescence at 657 nm with a relative quantum yield (RQY) 0.2 times that of rhodamine 6G powder. The compound belongs to a direct band gap at 1.91 eV, analyzed by Tauc's plot, and the energy is close to the PL position. The Hall effect measurement on a pressed pellet reveals an n-type conductivity with a carrier concentration of 3.358 × 1017 cm-3 and a mobility of 24.331 cm2 V-1 s-1. Furthermore, the compound produces a strong nonlinear third-harmonic generation (THG), with an χS(3) value of 1.3 × 105 pm2/V2 comparable to 1.6 × 105 pm2/V2 for AgGaSe2 measured at 800 nm.

Perovskite-like Framework Encapsulated with Fe-Based Magnetic Units in Ba10Fe3Sb7Se24.

Ba10Fe3Sb7Se24 was synthesized using a KBr flux at 850 °C (Crystal Data: orthorhombic, Cmc21, a = 9.3412(2) Å, b = 44.6666(10) Å, c = 12.5496(3) Å, V = 5236.2(2) Å3, and Z = 4). The compound adopts a new three-dimensional framework constructed by the layer to include Fe2Se6 dimers and FeSe4 tetrahedra in the linkage motifs of [Fe2SbSe10] and [FeSb6Se14], respectively. Alternatively, the all Sb-based polyhedra are assembled as a semiconducting, perovskite-like framework lacking an inversion center where these Fe-based magnetic units are trapped within the interstices. The strong antiferromagnetic interaction is revealed by a high Curie constant of -113 K, but the curvature of field-cooled and zero-field-cooled magnetic susceptibilities bifurcating at ∼19 K is observed. The critical temperature is well verified by a broad peak of χM″ signal showing a rapid increase below 19 K under an alternating current field. The Fe2Se6 dimer featuring distorted edge-sharing tetrahedra to induce the spin-canted antiferromagnetic ordering strongly dominates such magnetic ordering. Finally, a weak hysteresis loop is clearly observed at 2.0 K. This dilute magnetic selenide displays a direct bandgap at ∼1.54 eV, analyzed by the Tauc equation. Interestingly, the use of second-harmonic-generation temperature dependence shows a turning point at ∼20 ± 1 K, which precisely corresponds to the magnetic ordering temperature within the error bar, thereby demonstrating the versatility of the technique for probing magnetic phase transition.

Non-oxido divanadium(IV) and divanadium(V) thiolate complexes with a new type of chalcogenide bridging motif.

In our effort to study vanadium chalcogenide chemistry, we have synthesized and characterized a class of non-oxido divanadium(IV) and divanadium(V) complexes with chalcogenide and dichalcogenide as bridges. All structures consist of a similar divanadium motif, in which two metal centers are bridged by one µ-chalcogenide and one µ-η(2):η(2)-dichalcogenide, forming a V2(µ-E)(µ-η(2):η(2)-E2) (E = S or Se) core structure. These compounds are [V(IV)2(PS3)2(µ-Se2)(µ-Se)][PPh4]2 (1), [V(V)2(PS3'')2(µ-Se2)(µ-Se)] (2), [V(V)2(PS3'')2(µ-S2)(µ-S)] (3a) and [V(V)2(PS3)2(µ-S2)(µ-S)] (3b) ([PS3](3-) = P(C6H4-2-S)3 and [PS3''](3-) = P(C6H3-3-SiMe3-2-S)3). Compound 1 exhibits diamagnetic behavior, indicating strong antiferromagnetic coupling between two d(1) centers. Compounds 2 and 3a-b have the highest oxidation states for vanadium ions (+5/+5) among those reported divanadium chalcogenide clusters. The work demonstrates that high-valent divanadium chalcogenide clusters can be obtained with the activation of elemental chalcogens by low-valent vanadium ions.

Synthesis and characterization of three ytterbium coordination polymers featuring various cationic species and a luminescence study of a terbium analogue with open channels.

Four novel metal-organic frameworks with 4,4'-oxybis(benzoate) (OBA) ligands and suitable cationic species, [NH(3)(CH(2))(2)NH(3)](0.5)[Yb(OBA)(2)(H(2)O)] (1), (NH(4))[Yb(OBA)(2)(H(2)O)(2)] (2), Na[Yb(OBA)(2)] x 0.4 DMF x 1.5 H(2)O (3), and Na[Tb(OBA)(2)] x 0.4 DMF x 1.5 H(2)O (4), have been synthesized and structurally characterized. The two-dimensional structure of 1 possesses open channels filled with ethylenediamine cations. The two-dimensional structure of 2 contains the network featuring organic ligands with uncoordinated functional RCO(2) groups suspended within the windows. The three-dimensional structure of 3, in which Na(+) cations replaced the NH(4)(+) cations of 2 and the presence of DMF molecules, adopts an open framework with large rhombic channels. The evacuated phase "Na[Yb(OBA)(2)]" in 3 retained rigidity and crystallinity to a high temperature. Framework 4, a terbium analogue of 3, has the potential sensing ability; it exhibited gradually increasing luminescence intensities when dispersed sequentially in water, methanol, and ethanol as suspensions.

Tetra-butyl-ammonium bis-[4,4'-dimethyl-2,2'-(3,7-dimethyl-1H-4,2,1-benzothiaza-siline-1,1-di-yl)dibenzene-thiol-ato]vanadium(III) acetonitrile tetra-solvate.

In the title compound, [N(C(4)H(9))(4)][V(C(23)H(21)NS(3)Si)(2)]·4CH(3)CN, the V(III) atom (site symmetry ) is coordinated by two N,S,S'-tridentate 4,4'-dimethyl-2,2'-(3,7-dimethyl-1H-4,2,1-benzothiaza-siline-1,1-di-yl)dibenzene-thiol-ate ligands in a distorted trans-VN(2)S(4) octa-hedral geometry. The complete cation is generated by crystallographic twofold symmetry, with the V atom lying on the rotation axis. The unusual ligand arose from nucleophilic attack on the coordinated nitrile by the thiol-ate precursor and reduction of nitrile to the imidate.

Five related metal-organic frameworks constructed from [Ln2(SO4)2(H2O)n]2+ units and oxalate or acetate ligands.

We have synthesized a series of lanthanide-based metal-organic solids and characterized them through structural, magnetic and luminescence analyses. The nine compounds in the series NH(4)[Ln(SO(4))(H(2)O)(C(2)O(4))] [Ln = Ce, Nd, Eu, Gd (x2), Tb, Dy, Er, Yb] belong to four new three-dimensional (3D) structural groups, which we label CKMOF-4a, -4b, -5a, and -5b. The CKMOF-4a (Ce.) and -4b (Gd., Tb., Dy., Er., Yb.) structures feature [Ln(2)(SO(4))(2)(H(2)O)(2)](2+) units and C(2)O(4)(2-) ligands having the same symmetry operations, but their SO(4)(2-) anions feature different connective modes. These units are extended into one-dimensional ribbons fused together by oxalate ligands to form the two 3D open frameworks. The structures of CKMOF-5a (Nd.) and -5b (Eu., Gd.) comprise networks of c-glide-arranged [Ln(2)(SO(4))(2)(H(2)O)(2)](2+) units, in which the oxalate ligands are encapsulated within eight-membered rings. The networks are supported by distinct sites of oxalate ligands to form the two types of 3D open frameworks, the structural topologies of which are distinguished by the versatile connective modes of the SO(4)(2-) anions. The polymeric phases CKMOF-4b and -5b exist in the Gd analogues. For the Dy analogues, varying the size of the cation used as the template led to the selective precipitation of each of these two phases. The layer structure of [Gd(SO(4))(H(2)O)(2)(CH(3)CO(2))] (Gd.), labelled CKMOF-6, assembled from [Gd(2)(SO(4))(2)(H(2)O)(4)](2+) units and acetate ligands; the geometries of the [Gd(2)O(2)] rhombic units may induce ferromagnetic coupling at low temperature. Eu. and Tb. were luminescent, displaying red and green emissions, respectively.

Nanostructuring, compositional fluctuations, and atomic ordering in the thermoelectric materials AgPb(m)SbTe(2+m). The myth of solid solutions.

The nature of the thermoelectric materials Ag(1-x)Pb(m)SbTe(m+2) or LAST-m materials (LAST for Lead Antimony Silver Tellurium) with different m values at the atomic as well as nanoscale was studied with powder/single-crystal X-ray diffraction, electron diffraction, and high-resolution transmission electron microscopy. Powder diffraction patterns of different members (m = 0, 6, 12, 18, infinity) are consistent with pure phases crystallizing in the NaCl-structure-type (Fmm) and the proposition that the LAST family behaved as solid solutions between the PbTe and AgSbTe2 compounds. However, electron diffraction and high resolution transmission electron microscopy studies suggest the LAST phases are inhomogeneous at the nanoscale with at least two coexisting sets of well-defined phases. The minority phase which is richer in Ag and Sb is on the nanosized length scale, and it is endotaxially embedded in the majority phase which is poorer in Ag and Sb. Moreover, within each nanodomain we observe extensive long range ordering of Ag, Pb, and Sb atoms. The long range ordering can be confirmed by single crystal X-ray diffraction studies. Indeed, data collections of five different single crystals were successfully refined in space groups of lower symmetry than Fmm including P4/mmm and Rm. The results reported here provide experimental evidence for a conceptual basis that could be employed when designing high performance thermoelectric materials and dispel the decades long belief that the systems (AgSbTe2)(1-x)(PbTe)x are solid solutions.

Resonant states in the electronic structure of the high performance thermoelectrics AgPbmSbTe2+m: the role of Ag-Sb microstructures.

Ab initio electronic structure calculations based on gradient corrected density-functional theory were performed on a class of novel quaternary compounds AgPb(m)SbTe(2+m), which were found to be excellent high temperature thermoelctrics with a large figure of merit ZT approximately 2.2 at 800 K. We find that resonant states appear near the top of the valence and bottom of the conduction bands of bulk PbTe when Ag and Sb replace Pb. These states can be understood in terms of modified Te-Ag(Sb) bonds. The electronic structure near the gap depends sensitively on the microstructural arrangements of Ag-Sb atoms, suggesting that large ZT values may originate from the nature of these ordering arrangements.

Cubic AgPb(m)SbTe(2+m): bulk thermoelectric materials with high figure of merit.

The conversion of heat to electricity by thermoelectric devices may play a key role in the future for energy production and utilization. However, in order to meet that role, more efficient thermoelectric materials are needed that are suitable for high-temperature applications. We show that the material system AgPb(m)SbTe(2+m) may be suitable for this purpose. With m = 10 and 18 and doped appropriately, n-type semiconductors can be produced that exhibit a high thermoelectric figure of merit material ZTmax of approximately 2.2 at 800 kelvin. In the temperature range 600 to 900 kelvin, the AgPb(m)SbTe(2+m) material is expected to outperform all reported bulk thermoelectrics, thereby earmarking it as a material system for potential use in efficient thermoelectric power generation from heat sources.

CsPb3Bi3Te8 and CsPb4Bi3Te9: low-dimensional compounds and the homologous series CsPbmBi3Te5 + m.

Two new thermoelectric materials of quaternary bismuth telluride CsPb3Bi3Te8 and CsPb4Bi3Te9 are reported, which are members of a homologous series featuring anionic slabs [PbmBi3Te5 + m]- (m = 1-4) of monotonically increasing thickness.

CsMBi(3)Te(6) and CsM(2)Bi(3)Te(7) (M = Pb, Sn): new thermoelectric compounds with low-dimensional structures.

The new materials CsPbBi(3)Te(6) and CsPb(2)Bi(3)Te(7) were discovered through reactions of CsBi(4)Te(6) with PbTe, whereas the isostructural materials CsSnBi(3)Te(6) and CsSn(2)Bi(3)Te(7) were discovered through corresponding reactions with SnTe. The compounds can also be prepared from stoichiometric mixtures of Cs(2)Te, Pb (Sn), Bi, and Te. The crystal structures show a layered architecture of NaCl-type slabs alternating with layers of Cs atoms. This group of compounds offers a new quaternary system, Cs-M-Bi-Te (M = Pb and Sn), available for thermoelectric investigations, including fine-tuning of compositions and doping.

Cs(5)Mo(8)O(24)(OH)(2)AsO(4).2H(2)O and Cs(7)Mo(8)O(26)AsO(4): Two Novel Molybdenum(VI) Arsenates Containing Heteropolyanions [AsMo(8)O(30)H(2)](5)(-) and [AsMo(8)O(30)](7)(-).

Two novel molybdenum(VI) arsenates, Cs(5)Mo(8)O(24)(OH)(2)AsO(4).2H(2)O and Cs(7)Mo(8)O(26)AsO(4), have been prepared and their structures determined. Cs(5)Mo(8)O(24)(OH)(2)AsO(4).2H(2)O was synthesized by a high-temperature, high-pressure hydrothermal method and characterized by single-crystal X-ray diffraction, IR spectroscopy, and thermogravimetric analysis. Diffraction measurements were performed on a CCD area detector system. It crystallizes in the orthorhombic space group Cmcm with a = 8.8048(3) Å, b = 23.4314(9) Å, c = 16.0499(6) Å, and Z = 4. The structure consists of [AsMo(8)O(30)H(2)](5)(-) cluster anions which are made up of two tetranuclear {Mo(4)O(15)H} cores linked by an arsenic(V) atom. Upon heating, half of the structural unit first transforms to Cs(7)Mo(8)O(26)AsO(4), and the other half decomposes to Cs(3)AsO(4) and MoO(3) at higher temperature. Cs(7)Mo(8)O(26)AsO(4) crystallizes in the orthorhombic space group Ibca with a = 12.1247(4) Å, b = 22.9153(7) Å, c = 24.3777(7) Å, and Z = 8. It possesses [AsMo(8)O(30)](7)(-) cluster anions resembling to those found in the original structure. Cs(7)Mo(8)O(26)AsO(4) may be viewed as a dehydrated form of Cs(5)Mo(8)O(24)(OH)(2)AsO(4).2H(2)O from which the lability of [AsMo(8)O(30)H(2)](5)(-) with respect to dissociation of AsO(4)(3)(-) is first shown in the solid state. Structural differences between [AsMo(8)O(30)H(2)](5)(-) and [AsMo(8)O(30)](7)(-) are closely correlated with the cesium cations and water molecules present in the crystals. The title compounds are also the first structurally characterized examples in the Cs-Mo-As-O system.