Determination of the antimony valence state in Eu10Mn6Sb13

The antimony-121 M?ssbauer spectra of Eu10Mn6Sb13 have been measured between 2 and 295 K. Although the Zintl formalism indicates that the nine crystallographically distinct antimony sites in Eu10Mn6Sb13 should have formal valence states of -2, -1, 0, and +1, the M?ssbauer spectral isomer shifts reveal that the valence states of the different sites are all quite similar and correspond to an average electronic configuration for antimony of 5s(1.7)5p(4.0). This configuration corresponds to an excess of negative charge on the antimony of 0.7 or an average valence of -0.7, a valence which is rather consistent with the average antimony valence of -0.61 obtained from the Zintl formalism for the nine antimony sites in Eu10Mn6Sb13. The spectra obtained between 90 and 295 K are more consistent with the absence rather than the presence of any transferred magnetic hyperfine field at the antimony. In contrast, the spectra obtained at 2 and 5 K reveal the presence of an average transferred magnetic hyperfine field of ca. 8 T, a field that arises from the ferromagnetic ordering of the near-neighbor manganese(II) ions.     

Sr2MnSb2: a new ternary transition metal Zintl phase

A transition metal-containing Zintl phase, Sr2MnSb2, was prepared from a stoichiometric combination reaction of the elements in Sn flux, and its structure was determined by single-crystal X-ray diffraction methods. The compound crystallizes in the orthorhombic space group Pnma with a = 15.936(3) A, b = 14.498(3) A, c = 8.2646(17) A, and Z = 12. The structure of Sr2MnSb2 is composed of corrugated layers of corner- and edge-shared MnSb4 tetrahedra. The basic building unit of the layer is a [Mn3Sb6]12- cluster composed of three edge-shared MnSb4 tetrahedra. These trinuclear clusters share four Sb vertexes to form a layer with cavities. Sr2+ cations are located at the inter- and intralayer space. Magnetic susceptibility measurements indicate an effective magnetic moment of 4.85 mu(B), a value smaller than what would be expected from Mn2+ ions.     

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.     

Temperature-induced abrupt volume inflation in the mixed-valence ternary Zintl phase Yb8Ge3Sb5

The Zintl phase, Yb8Ge3Sb5 exhibits a complex lattice response and an abrupt negative thermal expansion below 15 K - subtle structural changes before and after the transition are consistent with temperature-induced electron transfer from (to) Yb 4f bands to (from) Sb 5p and Ge 4p bands.     

Ni5Sb17]4- transition-metal Zintl ion complex: crossing the Zintl border in molecular intermetalloid clusters

K3Sb7 and Ni(COD)2 react in the presence of 2,2,2-cryptand in ethylenediamine solutions ( approximately 1:8 Ni/Sb molar ratio) to give dark-brown crystals of the paramagnetic cluster anion [Ni5Sb17]4- as the [K(2,2,2-crypt)]+ salt. The cluster has a Ni(cyclo-Ni4Sb4) ring unit that sits inside a Sb13 bowl. The structure is similar to that of the previously reported [Pd7As16]4- ion containing a Pd(cyclo-Pd4As4) ring unit that sits inside a Pd2As12 bowl. Density functional theory and bond valence analyses suggest delocalized charge distributions and intermetallic-like properties.     

Synthesis, structure and properties of a new Zintl phase: SrLiSb

A new ternary antimonide SrLiSb has been synthesized and characterized using single-crystal X-ray studies. It is found to crystallize in the anti-PbCl₂ structure type with orthorhombic cell (centrosymmetric S.G., Pnma; , , ) and is isostructural to its calcium analogue (CaLiSb). However, BaLiSb has been reported to crystallize in the hexagonal space group P6₃/mmc. As in the Ca and Ba analogues, antimony is present as isolated Sb³⁻ ions making SrLiSb electron precise and hence is expected to behave as a classical Zintl compound. The magnetic susceptibility measurements show the diamagnetic nature and the conductivity is temperature independent, both verifying the classical Zintl nature of SrLiSb.     

Synthesis and characterization of transition-metal Zintl phases: Cs24Nb2In12As18 and Cs13Nb2In6As10 with isolated complex anions

The title compounds were prepared by direct reaction of the corresponding elements at high temperature. Their structures were determined by single-crystal X-ray diffraction (Cs24Nb2In12As18, triclinic, P1, Z=1, a=9.519(4), b=9.540(5), and c=25.16(1) A, alpha=86.87(4), beta=87.20(4), and gamma=63.81(4) degrees; Cs13Nb2In6As10, triclinic, P1, Z=1, a=9.5564(5), b=9.6288(5), and c=13.9071(7) A, alpha=83.7911(8), beta=80.2973(8), and gamma=64.9796(8) degrees). Cs24Nb2In12As18 and Cs13Nb2In6As10 contain isolated anions of [Nb2In12As18](24-) and [Nb2In6As10](13-), respectively. Each anion includes two cubane-like units made of one niobium, three indium, and four arsenic corners where a fifth arsenic atom completes the tetrahedral coordination at niobium, [(NbAs)In3As4]. In Cs13Nb2In6As10 these two units are connected via a direct In-In bond between two indium vertexes of the cubanes. In Cs24Nb2In12As18, on the other hand, the same two units are linked by a dimer made of semicubanes of [In3As4], i.e., a cubane with one missing vertex. Magnetic measurements show that Cs24Nb2In12As18 is diamagnetic, i.e., a d0 transition-metal Zintl phase, while Cs13Nb2In6As10 exhibits a Curie-Weiss behavior that corresponds to one unpaired electron.     

Synthesis,Structural Characterization,Electronic Structure,and Magnetic Properties of the Zintl Phase Eu10Cd6Bi12

A new transition‐metal‐containing Zintl phase, Eu₁₀Cd₆Bi₁₂, was synthesized by combining the elements in excess molten Cd. Single‐crystal X‐ray diffraction studies indicated that this compound crystallizes in the orthorhombic space group Cmmm (No. 65) with a=7.840(2), b=24.060(7), and c=4.7809(14) Å. The crystal structure of Eu₁₀Cd₆Bi₁₂ can be viewed as a stacking of a series of [Cd₆Bi₁₂] double layers, which are arranged alternately along the b axial direction. The layers are composed of corner‐ and edge‐shared CdBi₄ tetrahedra, a common feature in the crystal chemistry of many transition‐metal Zintl phases. Electronic‐band‐structure calculations confirm the closed‐shell configuration of all constituent elements and corroborate the electron count inferred by the Zintl formalism, that is, [Eu²⁺]₁₀[Cd²⁺]₆[Bi^3?]₈[Bi^2?]₄. Magnetic‐susceptibility measurements confirm the divalency of europium and show the existence of a long‐range antiferromagnetic order of the Eu spins below 12.3 K.     

Ionic-liquid-promoted decaborane olefin-hydroboration: a new efficient route to 6-R-B10H13 derivatives

Unlike in conventional organic solvents where transition metal catalysts are required, decaborane olefin-hydroboration reactions have been found to proceed in biphasic ionic-liquid/toluene mixtures with a wide variety of olefins, including alkyl, alkenyl, halo, phenyl, ether, ester, pinacolborane, ketone, and alcohol-substituted olefins, and these reactions now provide simple high-yield routes to 6-R-B10H13 derivatives. Best results were observed for reactions with bmimX (1-butyl-3-methylimidazolium, X = Cl(-) or BF4(-)) and bmpyX (1-butyl-4-methylpyridinium, X = Cl(-) or BF4(-)). Both the experimental data for these reactions and separate studies of the reactions of B10H13(-) salts with olefins indicate a reaction sequence involving (1) the ionic-liquid-promoted formation of the B10H13(-) anion as the essential initial step, (2) the addition of the B10H13(-) anion to the olefin to form a 6-R-B10H12(-) anion, and finally, (3) protonation of 6-R-B10H12(-) to form the final neutral 6-R-B10H13 product. The 6-R-B10H13 derivatives also undergo ionic-liquid-mediated dehydrogenative alkyne-insertion reactions in biphasic bmimCl/toluene mixtures, and these reactions provide high yield routes to 3-R-1,2-R' 2-1,2-C2B10H9 ortho-carborane derivatives.     

Negative magnetoresistance in a magnetic semiconducting Zintl phase: Eu(3)In(2)P(4)

A new rare earth metal Zintl phase, Eu(3)In(2)P(4), was synthesized by utilizing a metal flux method. The compound crystallizes in the orthorhombic space group Pnnm with the cell parameters a = 16.097(3) A, b = 6.6992(13) A, c = 4.2712(9) A, and Z = 2 (T = 90(2) K, R1 = 0.0159, wR2 = 0.0418 for all data). It is isostructural to Sr(3)In(2)P(4). The structure consists of tetrahedral dimers, [In(2)P(2)P(4/2)](6-), that form a one-dimensional chain along the c axis. Three europium atoms interact via a Eu-Eu distance of 3.7401(6) A to form a straight line triplet. Single-crystal magnetic measurements show anisotropy at 30 K and a magnetic transition at 14.5 K. High-temperature data give a positive Weiss constant, which suggests ferromagnetism, while the shape of susceptibility curves (chi vs T) suggests antiferromagnetism. Heat capacity shows a magnetic transition at 14.5 K that is suppressed with field. This compound is a semiconductor according to the temperature-dependent resistivity measurements with a room-temperature resistivity of 0.005(1) Omega m and E(g) = 0.452(4) eV. It shows negative magnetoresistance below the magnetic ordering temperature. The maximum magnetoresistance (Deltarho/rho(H)) is 30% at 2 K with H = 5 T.     

ZnTe6O13, a new ZnO–TeO2 phase

Our investigations into the ZnO–TeO₂ system have produced a new phase, zinc(II) hexatellurium(IV) tridecaoxide, ZnTe₆O₁₃, with trigonal (R) symmetry, synthesized by repeated heating and cooling to a maximum temperature of 1053 K. The asymmetric unit consists of a Zn atom coordinated in a distorted octahedral fashion by two unique tellurium(IV) oxide units that form trigonal–bipyramidal TeO₄ and TeO₃₊₁ corner‐ and edge‐shared polyhedra. Except for the Zn and an O atom, which occupy 6c positions, all atoms occupy 18f general positions.     

Crystal structure and a giant magnetoresistance effect in the new Zintl compound Eu3Ga2P4

Single-crystalline samples of a new Zintl compound, Eu(3)Ga(2)P(4), have been synthesized by a Ga-flux method. Eu(3)Ga(2)P(4) is found to crystallize in a monoclinic unit cell, space group C2/c, isostructural to Ca(3)Al(2)As(4). The structure is composed of a pair of edge-shared GaP(4) tetrahedra, which link by corner-sharing to form Ga(2)P(4) two-dimensional layers, separated by Eu(2+) ions. Magnetic susceptibility showed a Curie-Weiss behavior with an effective magnetic moment consistent with the value for Eu(2+) magnetic ions. Below 15 K, ferromagnetic ordering was observed and the saturation magnetic moment was 6.6 μ(B). Electrical resistivity measurements on a single crystal showed semiconducting behavior. Resistivity in the temperature range between 280 and 300 K was fit by an activation model with an energy gap of 0.552(2) eV. The temperature dependence of the resistivity is better described by the variable-range-hopping model for a three-dimensional conductivity, suggesting that Eu-P bonds are involved in the conductivity. A large magnetoresistance, up to -30%, is observed with a magnetic field H = 2 T at T = 100 K, suggesting strong coupling of carriers with the Eu(2+) magnetic moment.     

The crystal structure and magnetic properties of a new ferrimagnetic semiconductor: Ca21Mn4Sb18

Single crystals of the new transition metal Zintl phase, Ca(21)Mn(4)Sb(18), were prepared by high temperature melt synthesis. The crystal structure was determined by single crystal X-ray diffraction to be monoclinic in the space group C2/c. Crystal information was obtained at 90 K, and unit cell parameters were determined (a = 17.100(2) A, b = 17.073(2) A, c = 16.857(2) A, beta = 92.999(2) degrees, Z = 2, R1 = 0.0540, wR2 = 0.1437). The structure can be described as containing 4 discreet units per formula unit: 1 linear [Mn(4)Sb(10)](22-) anion, 2 dumbbell-shaped [Sb(2)](4-) anions, 4 individual Sb(3-) anions, and 21 Ca(2+) cations. The [Mn(4)Sb(10)](22-) anion contains four edge-shared MnSb(4) tetrahedra with distances between Mn ions of 3.388(4) A, 2.782(4) A, and 2.760(4) A. Electron counting suggests that the Mn are 2+. Temperature dependent magnetization shows a ferromagnetic-like transition temperature at approximately 52 K which is suppressed with increasing magnetic field. The paramagnetic regime is best fit to a ferrimagnetic model, providing a total effective moment of 4.04(2) mu(B), significantly less than that expected for 4 Mn(2+) ions (11.8 mu(B)). Temperature dependent resistivity shows that this compound is a semiconductor with an activation energy of 0.159(2) eV (100-300 K).     

Zintl phase variations through cation selection. Synthesis and structure of A21Cd4Pn18 (A = Eu, Sr, Ba; Pn = Sb, Bi)

Four new Zintl compounds, Ba21Cd4Sb18, Ba21Cd4Bi18, Sr21Cd4Bi18, and Eu21Cd4Bi18, have been synthesized and structurally characterized. Despite the similarity in their chemical formulas and regardless of their identical electronic requirements, the structures of the Ba compounds and the Sr and Eu compounds are subtly different. Due to the cations, a cleavage of a selected pnicogen-cadmium bond occurs and the structures adapt to a novel packing of the resultant heteronuclear anions.     

Yb8Ge3Sb5, a metallic mixed-valent Zintl phase containing the polymeric 1 infinity[Ge3 4-] anions

Yb8Ge3Sb5 is a nonclassical Zintl phase with metallic properties arising from the electropositive "spectator" cations of Yb. This compound contains the new Zintl anion 1infinity(Ge3)4- and is stabilized via a combination of Yb2+ and Yb3+ ions.     

Synthesis and Structure of Ba(2)Sn(3)Sb(6), a Zintl Phase Containing Channels and Chains

The new Zintl phase dibarium tritin hexaantimonide, Ba(2)Sn(3)Sb(6) has been synthesized, and its structure has been determined by single-crystal X-ray diffraction methods. It crystallizes in the orthorhombic space group -Pnma with a = 13.351(1) ?, b = 4.4100(5) ?, c = 24.449(3) ?, and Z = 4 (T = -50 degrees C). The structure of Ba(2)Sn(3)Sb(6) comprises large channels [010] defined by 30-membered rings constructed from an anionic framework. This framework is built up from Sn-centered trigonal pyramids and tetrahedra, as well as zigzag chains of Sb atoms. Within the channels reside the Ba(2+) cations and additional isolated zigzag Sb-Sb chains. The simultaneous presence of Sn trigonal pyramids and tetrahedra implies that Ba(2)Sn(3)Sb(6) is a mixed-valence compound whose oxidation state notation can be best represented as (Ba(2+))(2)[(Sn(II))(2)(Sn(IV))(Sb(-)(III))(3)(Sb(-)(I))](2)(-)[(Sb(-)(I))(2)](2)(-).     

Sr6Cd2Sb6O7S10: Strong SHG Response Activated by Highly Polarizable Sb/O/S Groups

A new nonlinear optical (NLO) oxysulfide, Sr₆Cd₂Sb₆O₇S₁₀, which contains the functional groups [SbO_xS_5?x]^7? (x=0, 1) with a 5s² electron configuration, is synthesized by a solid‐state reaction. This compound displays a phase‐matchable second harmonic generation (SHG) response four times stronger than AgGaS₂ (AGS) under laser irradiation at 2.09 μm. Single‐crystal‐based optical measurements reveal a SHG intensity that can be tuned by temperature and novel photoluminescence properties. Theoretical analyses demonstrate that tetragonal [SbOS₄]^7? and [SbS₅]^7? pyramids make the predominant contribution to the enhanced SHG effect. Among those, the [SbOS₄]^7? units with mixed anions make a larger contribution. This work proposes that oxysulfide groups with an ns² electron configuration can serve as new functional building units in NLO materials and opens a new avenue for the design of other optoelectronic materials.     

PKU-10: a new 3D open-framework germanate with 13-ring channels

PKU-10, a germanate with the formula [(CH(3))(4)N](3)Ge(11)O(19)(OH)(9), is synthesized under hydrothermal conditions, and its structure is determined by single-crystal X-ray diffraction data. PKU-10 possesses 3D intersected 13-ring channels and presents a new 6-connectedness linkage mode of the Ge(7) cluster, T(3)P(2)O, forming a pcu topological network. Each Ge(7) cluster is, in fact, surrounded by eight Ge(7) clusters in a nearly perfect cube because the hydrogen bonds between Ge(7) clusters are also taken into account. The structure-directing agent tetramethylammonium (TMA(+)) ions, locating in the channels, can be partially exchanged by Li(+) with retention of the germanate framework. The germanate framework collapses with decomposition of the TMA(+) ions at temperatures higher than 240 °C.     

Na7Sn12: a binary Zintl phase with a two-dimensional covalently bonded tin framework

Na(7)Sn(12) was synthesized by quenching of stoichiometric amounts of the elements (700 degrees C) in a sealed niobium ampule and further thermal treatment at 270 degrees C for 40 days. Single crystals of Na(7)Sn(12) were obtained from a mixture with the composition Na(6)SrSn(16). The structure of Na(7)Sn(12) consists of two-dimensional polyanions 2 (infinity) [Sn(12)(7-)], which are separated by Na atoms. Bonding Sn-Sn contacts in the polyanion vary between 2.827(2) and 3.088(2) A. Crystal data: monoclinic, P2/n, Z = 4, a = 13.375(3) A, b = 9.239(2) A, c = 17.976(4) A, gamma = 90.15(3) degrees, V = 2243.0(8) A(3), mu = 13.22 mm(-1), d(calc) = 4.694 g cm(-3), R1(F) = 6.1% (for all reflections). Extended-Hückel tight-binding calculations with the implementation the electron localization function (ELF) reveal that Na(7)Sn(12) can be viewed as an intermetallic compound with exclusively localized bonding and nonbonding regions as expected from the 8 - N rule. Thus Na(7)Sn(12) is a Zintl phase with the formula (Na(+))(7)[(2b)Sn(2)(-)](1)[(3b)Sn(-)](5)[(4b)Sn(0)](6).