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PubMed2004

A detailed study of the vapochromic Behavior of [Tl[Au(C6Cl5)2]]n.

The linear-chain polymer [Tl[Au(C(6)Cl(5))(2)]](n), 1, reacts in the solid state and in solution with different volatile organic compounds such as tetrahydrofuran, acetone, tetrahydrothiophene, 2-fluoropyridine, acetonitrile, acetylacetone, and pyridine. Solid-state exposure of 1 to vapors of the above VOCs produces a selective and reversible change in its color that is perceptible to the human eye and even deeper under UV irradiation, allowing 1 to function as a sensor for these VOCs. Heating the samples exposed to the VOCs for a few minutes at 100 degrees C regenerates the original material without degradation, even after several exposure/heating cycles. The reversibility is further confirmed by X-ray powder diffraction measurements of complex 1 before and after exposure to vapors and again after heating the samples. The products obtained by reactions of complex 1 with the above VOCs as ligands in solution contain extended linear chains of alternating gold and thallium centers with two molecules of the organic ligands attached to each thallium atom. The stoichiometry of these materials has been confirmed by single-crystal X-ray diffraction as [Tl(THF)(2)[Au(C(6)Cl(5))(2)]](n), 3, and [Tl(acacH)(2)[Au(C(6)Cl(5))(2)]](n), 5. Comparison of FT-IR, UV-vis, and luminescence spectra at room temperature and at 77 K of the solid samples of complexes 2-9 with the spectra of complex 1 after its exposure to VOCs suggests interaction occurs between the organic VOCs and thallium in each case. Thermogravimetric analyses data indicate that all the thallium centers in these derivatives of complex 1 are neither fully nor equally coordinatively saturated. The materials formed appear to be intermediates between complex 1 with no VOCs attached and complexes 3-9 which contain two organic ligands coordinated to each thallium. A crystal structure analyses of one of these intermediates, [Tl(THF)(0.5)[Au(C(6)Cl(5))(2)]](n), 1.0.5THF, confirms this. Density functional calculations are in accord with the observed experimental results. Analysis reveals a substantial participation of the metal atoms in transitions that give rise to the observed emissions. Crystallographic data are as follows. For 1.0.5THF: triclinic, P1, a = 8.9296(1) A, b = 11.2457(1) A, c = 21.2465(3) A, alpha = 96.7187(7) degrees, beta = 92.5886(6) degrees, gamma = 98.5911(8) degrees, V = 2090.87(4) A(3), and Z = 2. For 3: monoclinic, P2(1)/c, a = 26.4163(6) A, b = 12.1619(2) A, c = 28.0813(6) A, alpha = 90 degrees, beta = 161.9823(6) degrees, gamma = 90 degrees, V = 2790.51(10) A(3), and Z = 4. For 5: monoclinic, P2(1)/c, a = 9.8654(2) A, b = 29.8570(5) A, c = 11.6067(2) A, alpha = 90 degrees, beta = 114.5931(6) degrees, gamma = 90 degrees, V = 3108.64(10) A(3), and Z = 4.

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PubMed2005

Mn(II) staircase structures stitched by water clusters to a 3D metal-organic open framework: X-ray structural and magnetic studies.

4-Hydroxypyridine-2,6-dicarboxylic acid (chelidamic acid, cdaH2) reacts with Mn(OAc)2 x 4H2O to form a 1D staircase structure with dimeric Mn(II) units connected by water clusters to form a 3D framework, {[Mn2(cda)2 x 4H2O] x 4H2O}n, 1, in aqueous pyridine at room temperature. The compound crystallizes in the triclinic space group P1 with a = 9.495(3), b =10.733(5), c = 11.065(4) A, alpha = 87.42(5), beta = 74.14(5), gamma = 80.07(2) degrees, U = 1068.5(9) A3, Z = 2, rho(calcd) = 1.915 g cm(-3), T = 100 K, mu = 1.28 mm(-1), R1 = 0.0453 (I > 2sigma(I)), wR2 = 0.1046, GOOF = 1.282. Upon removal of the water molecules by heating, the 3D structure breaks down. Thermogravimetric analysis, infrared, X-ray powder diffraction studies, and X-ray crystallography were performed to characterize this compound. Since the coordination polymer has diaqua-bridged Mn(II) centers, it was subjected to variable-temperature magnetic studies.

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PubMed2005

Inorganic-organic hybrids formed by P,P'-diphenylmethylenediphosphinate, pcp2-, with the Cu2+ ion. X-ray crystal structures of [Cu(pcp)(H2O)2] x H2O and [Cu(pcp)(bipy)(H2O)].

Weakly coordinated [Cu(pcp)(H2O)n] complexes are formed in aqueous solution, at room temperature, by interaction of P,P'-diphenylmethylene diphosphinic acid (H2pcp) with copper(II) ions. However, heating of the solutions gives rise to the formation of two extended metal-oxygen networks of formulas [Cu(pcp)(H2O)2] x H2O, 1, and [Cu(pcp)(H2O)2], 2. In the presence of 2,2'-bipyridyl (bipy) the diamine derivative [Cu(pcp)(bipy)(H2O)], 4, has been isolated. Complex 1 easily loses water to form a monohydrated derivative [Cu(pcp)H2O], 3, whereas 2 is completely dehydrated after prolonged heating at 150 degrees C, under vacuum. The compounds 1 and 2 have substantially different solid-state structures as shown by X-ray powder diffraction spectra, IR spectra, and thermogravimetric analyses. Consistently, the two complexes cannot be directly interconverted and present different dehydration pathways. Rehydration of these materials in both cases allows quantitative formation of 1. X-ray analysis established that the structure of 1 consists of a corrugated two-dimensional layered polymeric array, where infinite zigzag chains of Cu centers and bridging phenylphosphinate ligands are linked together through strong hydrogen-bonding interactions; the structure of 4 consists of monodimensional polymers, where the hydrogen-bonding interactions play an essential bridging role in the extended architecture. In both structures the metal center displays a five-coordinate environment with approximate square pyramidal geometry, with the pcp ligand acting as bidentate and monodentate in 1 and solely as bidentate in 4. In 1 the coordination sphere is completed through water molecules; in 4, through water and diamine ligands. The thermogravimetric analyses of the complexes are compared with those of the related hybrids [M(pcp)(H2O)3] x H2O, where M = Mn, Co, or Ni, confirming that noncoordinated water molecules also play a basic role in determining the molecular packing.

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PubMed2005

Fabrication of ZnSe nanoparticles in the apoferritin cavity by designing a slow chemical reaction system.

Zinc selenide nanoparticles (ZnSe NPs) were synthesized in the cavity of the cage-shaped protein apoferritin by designing a slow chemical reaction system, which employs tetraaminezinc ion and selenourea. The chemical synthesis of ZnSe NPs was realized in a spatially selective manner from an aqueous solution, and ZnSe cores were formed in almost all apoferritin cavities with little bulk precipitation. Three factors are found to be important for ZnSe NP synthesis in the apoferritin cavity: (1) the threefold channel, which selectively introduces zinc ion into the apoferritin cavity, (2) the apoferritin internal potential, which favors zinc ion accumulation in the cavity, and (3) the nucleation site, which nucleates ZnSe inside the cavity. The characterization of the synthesized ZnSe NPs by X-ray powder diffraction and energy-dispersive spectrometry revealed that the synthesized NPs are a collection of cubic ZnSe polycrystals. It was shown that the 500 degrees C heat treatment for 1 h under nitrogen gas transformed the polycrystalline ZnSe core into a single crystal, and single-crystal ZnSe NPs free of protein were obtained.

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PubMed2005

Tribasic lead maleate and lead maleate: synthesis and structural and spectroscopic characterizations.

We report on the synthesis and structure of tribasic lead maleate hemihydrate ([Pb4O3]C2H2(CO2)2.(1/2)H2O, TRIMAL) and lead maleate (PbC2H2(CO2)2, PBMAL). The structure of [Pb4O3]C2H2(CO2)2.(1/2)H2O, solved ab initio from X-ray powder diffraction data, consists of infinite slabs of edge-sharing OPb4 tetrahedra, of composition [Pb4O3], running along the c axis and linked together into a three-dimensional network by tetradentate maleate anionic ligands. The structure of PbC2H2(CO2)2, solved from single crystal diffraction data, is lamellar and contains double layers of heptacoordinated lead atoms, bonded only to the oxygen atoms of the maleate ligands. In both compounds, lead is in the oxidation state 2+ and the coordination polyhedra around the Pb2+ exhibit a hemidirected geometry and are strongly distorted as a result of the lone pair of electrons. The absence of protons on the acidic portion of the maleate moieties was confirmed by Raman spectroscopy and by 1H MAS and 1H-13C CP MAS NMR experiments. The two compounds were further characterized using chemical and thermogravimetric analyses.

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PubMed2005

Inorganic-organic hybrids of the p,p'-diphenylmethylenediphosphinate, pcp2-. Synthesis, characterization, and XRPD structures of [Sn(pcp)] and [Cu(pcp)].

Two new inorganic-organic polymeric hybrids [Sn(pcp)] and [Cu(pcp)], pcp=CH2(PhPO2)2(2-), have been synthesized and structurally characterized. The tin derivative has been obtained by reaction of the p,p'-diphenylmethylenediphosphinic acid (H2pcp) in water with SnCl2.2H2O, while the copper derivative has been synthesized through a hydrothermal reaction from the same H2pcp acid and Cu(O2CMe)2.H2O. The structures of these compounds have been solved "ab initio" by X-ray powder diffraction (XRPD) data. [Sn(pcp)] has a ladder-like polymeric structure, with tin(II) centers bridged by diphenylmethylenediphosphinate ligands, and alternating six- and eight-membered rings. The hemilectic coordination around the metal shows the tin(II) lone pair to be operative, resulting in significant interaction mainly with a C-C bond of one phenyl ring. The [Cu(pcp)] complex displays a polymeric columnar structure formed by two intersecting sinusoidal ribbons of copper(II) ions bridged by the bifunctional phosphinate ligands. The intersections of the ribbons are made of dimeric units of pentacoordinated copper ions. Crystal data for [Sn(pcp)]: monoclinic, space group P2(1)/c, a=11.2851(1), b=15.4495(6), c=8.6830(1) A, beta=107.546(1) degrees, V=1443.44(9) A, Z=4. Crystal data for [Cu(pcp)]: triclinic, space group P, a=10.7126(4), b=13.0719(4), c=4.9272(3) A, alpha=92.067(5), beta=95.902(7), gamma=87.847(4) degrees, V=685.47(7), Z=2. The tin compound has been characterized by 119Sn MAS NMR (magic-angle spinning NMR), revealing asymmetry in the valence electron cloud about tin. Low-temperature magnetic measurements of the copper compound have indicated the presence of weak antiferromagnetic interactions below 50 K.

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PubMed2005

Metal-organic framework H-bonded like a polycatenane: coexistence of acyclic water trimer and nonamer.

Pyridine-2,6-dicarboxylic acid and 1,2-di-4-pyridylethylene react hydrothermally with nickel(II) nitrate, forming a metal-organic framework that forms a polycatenane-like structure through H-bonding interactions between water molecules and carboxylate O atoms with void spaces. Discrete acyclic trimeric and nonameric water clusters occupy the voids in the structures. X-ray powder diffraction and X-ray structure analysis have been used to characterize this compound. Crystal data for 1 {(3dpeH(2))[Ni(pdc)(2)](3).15H(2)O}: monoclinic space group P2(1)/c, a = 24.730(5) Angstroms, b = 19.895(2) Angstroms, c = 17.257(4) Angstroms, beta = 104.832(5) degrees, V = 8208(4) Angstroms(3), Z = 4, R1 = 0.0429, wR2 = 0.1072, and S = 1.051.

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PubMed2005

Camouflaged carborane amphiphiles: synthesis and self-assembly.

A series of amphiphilic amine hydrochloride salts of B-polymethylated (camouflaged) (aminoalkyl)- and bis(aminoalkyl)carboranes have been designed and synthesized in high yield for the purpose of constructing novel carborane-based nanomaterials. Due to the distinct separation of the hydrophobic and hydrophilic regions within each salt, the mono- and disubstituted amphiphiles spontaneously self-assembled upon sonication into rod-shape micro/nanostructures in aqueous solutions. The effects of concentration, method of dispersion, solvent, chain length, counterion, ionic charge, and underlying carborane cage structure on the formation of the these rod products were investigated. The microrods have been studied by transmission electron microscopy (TEM), optical microscopy, X-ray powder diffraction (XRD), thermogravimetric/differential thermal analysis (TG/DTA), and FTIR. For the first time, this work clearly demonstrates the self-assembly of B-polymethylated carboranes into supramolecular structures.

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PubMed2005

Synthesis and characterization of the open-framework barium bisphosphonate [Ba3(O3PCH2NH2CH2PO3)2(H2O)4].3H2O.

Following the strategy of using polyfunctional phosphonic acids for the synthesis of open-framework metal phosphonates, the phosphonocarboxylic acid (H2O3PCH2)2NCH2C6H4COOH was used in the hydrothermal synthesis of new Ba phosphonates. Its decomposition led to the first open-framework barium phosphonate [Ba3(O3PCH2NH2CH2PO3)2(H2O)4].3H2O. The synthesis was also successfully performed using iminobis(methylphosphonic acid), (H2O3PCH2)2NH, as a starting material, and the synthesis was optimized to obtain as a pure material. The reaction setup as well as the pH are the dominant parameters, and only a diffusion-controlled reaction led to the desired compound. The crystal structure was solved from single-crystal data: monoclinic; C2/c; a=2328.7(2), b=1359.95(7), and c=718.62(6) pm; beta=98.732(10) degrees ; V=2249.5(3)x10(6) pm3; Z=4; R1=0.036; and wR2=0.072 (all data). The structure of [Ba3(O3PCH2NH2CH2PO3)2(H2O)4].3H2O is built up from BaO8 and BaO10 polyhedra forming BaO chains and layers, respectively. These are connected to a three-dimensional metal-oxygen-metal framework with the iminobis(methylphosphonic acid) formally coating the inner walls of the pores. The one-dimensional pores (3.6x4 A) are filled with H2O molecules that can be thermally removed. Thermogravimetric investigations and temperature-dependent X-ray powder diffraction demonstrate the stability of the crystal structure up to 240 degrees C. The uptake of N,N-dimethylformamide and H2O by dehydrated samples is demonstrated. Furthermore, IR, Raman, and 31P magic-angle-spinning NMR data are also presented.

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PubMed2005

Investigation of the crystal structure and the structural and magnetic properties of SrCu2(PO4)2.

SrCu2(PO4)2 was prepared by the solid-state method at 1153 K. Its structure was solved by direct methods in the space group Pccn (No. 56) with Z = 8 from synchrotron X-ray powder diffraction data measured at room temperature. Structure parameters were then refined by the Rietveld method to obtain the lattice parameters, a = 7.94217(8) A, b = 15.36918(14) A, and c = 10.37036(10) A. SrCu2(PO4)2 presents a new structure type and is built up from Sr2O16 and Cu1Cu2O8 units with Cu1...Cu2 = 3.256 A. The magnetic properties of SrCu2(PO4)2 were investigated by magnetic susceptibility, magnetization up to 65 T, Cu nuclear quadrupole resonance (NQR), electron-spin resonance, and specific heat measurements. With spin-dimer analysis, it was shown that the two strongest spin-exchange interactions between Cu sites result from the Cu1-O...O-Cu2 and Cu2-O...O-Cu2 super-superexchange paths with Cu1...Cu2 = 5.861 A and Cu2...Cu2 = 5.251 A, and the superexchange associated with the structural dimer Cu1Cu2O8 is negligible. The magnetic susceptibility data were analyzed in terms of a linear four-spin cluster model, Cu1-Cu2-Cu2-Cu1 with -2J(1)/kB = 82.4 K for Cu1-Cu2 and -2J(2)/k(B) = 59 K for Cu2-Cu2. A spin gap deduced from this model (Delta/kB = 63 K) is in agreement with that obtained from the Cu NQR data (Delta/kB = 65 K). A one-half magnetization plateau was observed between approximately 50 and 63 T at 1.3 K. Specific heat data show that SrCu2(PO4)2 does not undergo a long-range magnetic ordering down to 0.45 K. SrCu2(PO4)2 melts incongruently at 1189 K. We also report its vibrational properties studied with Raman spectroscopy.

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PubMed2006

Synthesis and characterization of Prussian blue analogues incorporating the edge-bridged octahedral [Zr6BCl12]2+ cluster core.

In attempts to produce a microporous magnet, two approaches were explored for expanding the Prussian blue structure type via incorporation of edge-bridged octahedral [Zr(6)ZCl(12)](2+) (Z = B, Be) cluster cores. Dissolution of Rb(5)Zr(6)BCl(18) and K(5)Zr(6)BeCl(15) in an acetonitrile solution of Et(4)N(CN) led to the isolation of (Et(4)N)(5)[Zr(6)BCl(12)(CN)(6)] (1) and (Et(4)N)(5)[Zr(6)BeCl(12)(CN)(6)].2MeCN.2THF (2), respectively. The crystal structure of 1.1.5MeCN revealed the expected cyano-terminated cluster complex with a trans-N...N span of 11.73(3) Angstroms. Unfortunately, both [Zr(6)ZCl(12)(CN)(6)](5-) clusters rapidly lose their cyanide ligands in aqueous solution making them ill-suited for solid-forming reactions with hydrated metal ions. Such outer-ligand exchange, however, allows the use of [Zr(6)BCl(18)](4-) in the synthesis of expanded Prussian blue-type solids through reactions with [Cr(CN)(6)](3-). The use of 2.2 M aqueous LiCl to stabilize the cluster during the reaction gave (Et(4)N)(2)[Zr(6)BCl(12)][Cr(CN)(6)]Cl.3H(2)O (3), while the use of 1 M acetic acid yielded (Et(4)N)(2)[Zr(6)BCl(12)][Cr(CN)(6)]Cl.2H(2)O.CH(3)CO(2)H (4). A Rietveld refinement against X-ray powder diffraction data collected for 3 confirmed the presence of a cubic Prussian blue framework structure, featuring alternating [Zr(6)BCl(12)](2+) cores and [Cr(CN)(6)](3-) anions. The temperature dependence of magnetization data obtained for 4 revealed activation of magnetic exchange interactions between the S = (1)/(2) cluster units and the S = (3)/(2) hexacyanochromate complexes below 10 K.

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PubMed2005

Crystal structures and magnetic properties of mixed iridium-ruthenium triple perovskites. 1. Ba3MRuIrO9 (M=Lanthanide, Y).

Crystal structures and magnetic properties of Ba3MRuIrO9 (M=lanthanides, Y) were investigated. Rietveld refinements using powder diffraction data indicate that all the compounds crystallize in the 6H-BaTiO3 structure type in space group P63/mmc. Magnetic susceptibility measurements were carried out on each compound. Effective magnetic moments were smaller than values estimated using spin-only moments, which indicate the presence of spin-orbit coupling and strong interactions in the [(Ru0.5Ir0.5)2O9] face-sharing octahedra that contain a disordered mixture of Ru and Ir on a single crystallographic site. Magnetic anomalies were observed for the compounds Ba3PrRuIrO9, Ba3TbRuIrO9, and Ba3NdRuIrO9 at 3.5, 13, and 8 K, respectively.

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PubMed2005

Crystal structures and magnetic properties of mixed iridium-ruthenium triple perovskites. 2. Ba3MRuIrO9 (M=Li, Na, Mg, Ni, Zn, Bi, In).

Crystal structures and magnetic properties of polycrystalline Ba3MRuIrO9 (M1+=Li, Na; M2+=Mg, Ni, Zn; M3+=Bi, In) were investigated. Rietveld refinements of the crystal structures using powder diffraction data indicate that, with the exception of Ba3BiRuIrO9, all compounds crystallize in the 6H-BaTiO3 structure type in space group P63/mmc; Ba3BiRuIrO9 crystallizes in space group C2/c. The 6H-BaTiO3, or triple-perovskite, structure is composed of hexagonal and cubic stacking of [AO3] layers and contains face- and corner-sharing octahedra. The structures in this study contain a disordered mixture of Ir and Ru in the face-sharing octahedra dimers, which are connected via corner-shared MO6 octahedra. Magnetic susceptibility measurements as a function of temperature were carried out on each compound. Effective magnetic moments were smaller than values estimated using spin-only moments, which indicate the presence of spin-orbit coupling and strong interactions in the face-sharing octahedra that contain a disordered mixture of Ru and Ir on a single crystallographic site. Over a broad temperature range, a divergence of the zero-field-cooled and field-cooled data were observed for Ba3MgRuIrO9, Ba3NiRuIrO9, Ba3ZnRuIrO9, and Ba3LiRuIrO9.

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PubMed2005

Characterization and ab initio XRPD structure determination of a novel silicate with Vierer single chains: the crystal structure of NaYSi2O6.

The crystal structure of a sodium yttrium silicate with composition NaYSi2O6 has been determined from laboratory X-ray powder diffraction data by simulated annealing, and has been subsequently refined with the Rietveld technique. The compound is monoclinic with space group P2(1)/c and unit cell parameters of a=5.40787(2) A, b=13.69784(5) A, c=7.58431(3) A, and beta=109.9140(3) degrees at 23.5 degrees C (Z=4). The structure was found to be a single-chain silicate with a chain periodicity of four. The two symmetry dependent [Si4O12] chains in the unit cell are parallel to c. A prominent feature is the strong folding of the crankshaft-like chains within the b,c-plane resulting in intrachain Si-Si-Si angles close to 90 degrees. The coordination of the Y3+ ions by O2- is 7-fold in the form of slightly irregular pentagonal bipyramids, with oxygen atoms from four different chains contributing to the coordination polyhedron. Na+ ions are irregularly coordinated by 10 oxygens from two neighboring chains. No disorder of Na+ and Y3+ between the two nontetrahedral cation sites could be observed. Furthermore, micro-Raman spectra have been obtained from the polycrystalline material.

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PubMed2006

New cubic perovskite Na(Cu2.5Ti0.5)Ti4O12 with square planar coordination of Ti4+.

A new perovskite, Na[Cu(2.5)Ti(0.5)]Ti4O12, has been synthesized using a conventional solid-state technique. Neutron and synchrotron X-ray powder diffraction studies in combination with density measurements and bond-valence calculations have revealed that the material crystallizes in the cubic Im space group (a = 7.38472(2) A, Z = 2) with the square-plane site accommodating 16.7% of Ti4+. This is the highest level of non-Jahn-Teller cation substitution for Cu2+ reported to date for CaCu3Ti4O12-type perovskites prepared at ambient pressure.

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PubMed2006

Anion influence on the structures of a series of copper(II) metal-organic frameworks.

The main aim of the work herein presented is to investigate the influence of different anions on the overall structure of a series of metal-organic frameworks. The reactions between CuCl2, Cu(OAc)2, and CuSO4 and the two bipyridylurea ligands L1 and L2 [L1 = 1,3-bis(pyridin-4-ylmethyl)urea; L2 = 1,3-bis(pyridin-3-ylmethyl)urea; see Scheme 1 in paper] have been carried out and the crystal structure of five of the resulting metal-organic assemblies determined. These crystal structures have shown that the geometry and size of the corresponding anions together with their coordinating and hydrogen-bonding properties are essential in determining the final structures of the assemblies. Particularly interesting, because of their potential as nanoporous materials, are the assemblies obtained from the reaction between each of the two ligands (L1 and L2) and CuCl2, which yield noninterpenetrating 2D metal-organic layers made of squares of ca. 15 x 15 Angstroms. These layers stack on top of each other, producing infinite 3D channels filled with solvent molecules. The thermal stabilities of the five metal-organic frameworks prepared have been studied by means of thermogravimetric analysis. Preliminary X-ray powder diffraction studies of one of these metal-organic frameworks indicate that upon heating the assembly changes to a different crystalline structure. Interestingly, the original structure reforms upon exposure of this sample to traces of water.

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PubMed2006

Structure determination and relative properties of novel noncentrosymmetric borates MM'4(BO3)3 (M = Na, M' = Ca and M = K, M' = Ca, Sr).

A series of novel noncentrosymmetric borates, MM'4(BO3)3 (M = Na, M' = Ca; M = K, M' = Ca, Sr), have been successfully synthesized via a standard solid-state reaction. The crystal structures have been determined by the SDPD (structure determination from powder diffraction) method. They crystallize in the noncentrosymmetric space group Ama2 with the following lattice parameters: a = 10.68004(11) A, b = 11.28574(11) A, c = 6.48521(6) A for NaCa4(BO3)3; a = 10.63455(10) A, b = 11.51705(11) A, c = 6.51942(6) A for KCa4(BO3)3; and a = 11.03843(8) A, b = 11.98974(9) A, c = 6.88446(5) A for KSr4(BO3)3. The fundamental building units are isolated BO3 anionic groups. Their second harmonic generation (SHG) coefficients were one-half (NaCa4(BO3)3), one-third (KCa4(BO3)3), and two-thirds (KSr4(BO3)3) as large as that of KH2PO4 (KDP). The infrared and UV-vis spectra of the three compounds are discussed. Moreover, a comparison of the structures of these novel compounds and three other novel cubic compounds with the same formula, MM'4(BO3)3 (M = Li, M' = Sr; M = Na, M' = Sr, Ba), is presented here.

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PubMed2006

Design of a new family of inorganic compounds Ae2F2SnX3 (Ae = Sr, Ba; X = S, Se) using rock salt and fluorite 2D building blocks.

We could predict the structure of a new family of compounds Ae(2)F(2)SnX(3) (Ae = Sr, Ba; X = S, Se) from the stacking of known 2D building blocks of the rock salt and fluorite types. With a high-temperature ceramic method we have then succeeded to synthesize the four compounds Ba(2)F(2)SnS(3), Ba(2)F(2)SnSe(3), Sr(2)F(2)SnS(3), and Sr(2)F(2)SnSe(3). The structure refinements from X-ray powder diffraction patterns have confirmed the structure predictions and showed their good accuracy. The structure of the four compounds results from the alternated stacking of fluorite [Ae(2)F(2)] (Ae = Sr, Ba) and distorted rock salt [SnX(3)] (X = S, Se) 2D building blocks. As shown by band structure calculations, these blocks behave as a charge reservoir and a charge acceptor, respectively. Sr(2)F(2)SnS(3) and Ba(2)F(2)SnS(3) are transparent with optical gaps of 3.06 and 3.21 eV, respectively. However, an attempt to obtain a transparent conductor by substituting Ba per La in Ba(2)F(2)SnS(3) was unsuccessful.

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