Showing papers on "Isostructural published in 2004"

Intensely luminescent gold(I)-silver(I) cluster complexes with tunable structural features.

Abstract: A new series of isostructural, brilliantly luminescent gold−silver complexes having the formula [Au3(μ3-E)Ag(PPh2py)3](BF4)2 where E = O, S, Se and Ph2Ppy = 2-diphenylphosphinopyridine has been synthesized and characterized. The structural core of these complexes is a Au3Ag metallophilically linked tetrahedron with a group-16 atom functioning as a μ3-ligand capping the three gold atoms. In the solid state, pairs of clusters are joined by two unsupported aurophilic interactions. The emission energy changes strikingly in going from O (blue) to S (yellow) and Se (orange). The luminescence from the E = O system is the first to be reported for a gold(I) oxo system. Additionally, the luminescent 4-methylpyridyl analogue with E = S has been prepared and structurally characterized. For E = S, Se, the change in emission energy with μ3-bridging atom provides a sound basis for an LMMCT assignment of the excited state while lifetime measurements support its spin-forbidden nature. Frozen glass measurements indicate th...

Cation−Cation Interactions between Uranyl Cations in a Polar Open-Framework Uranyl Periodate

Abstract: Novel open-framework alkali metal uranyl periodates, having the formula A[(UO2)3(HIO6)(OH)(O)(H2O)]·1.5H2O (A = Li, Na, K, Rb, Cs), have been prepared through mild hydrothermal synthesis. These isostructural compounds contain distorted UO7 pentagonal bipyramids that are linked through a uranyl (UO22+) to uranyl cation−cation interaction. This interaction arises from a single axial uranyl oxygen coordinating at an equatorial site of an adjacent uranyl unit. These uranium oxide polyhedra are further bound by IO6 distorted octahedra creating an open-framework structure whose channels contain the alkali metal cations.

Two polymorphs of cobalt(II) imidazolate polymers synthesized solvothermally by using one organic template N,N-dimethylacetamide.

Abstract: Two structurally different polymorphs of cobalt(II) imidazolate frameworks are solvothermally synthesized by using N,N-dimethylacetamide as a template: The polymorph 6 (a = 9.797 (4) A, b = 15.301(6) A, c =14.902(6) A, β = 98.904(6)°, monoclinic, P21/n) shows structures of silicate CaAl2Si2O8 with CrB4 topology, while polymorph 7 (a = 15.173(4) A, b = 15.173(4) A, c = 19.089(5) A, Pbca) shows CaGa2O4-related topological structures. In addition, the 7‘ (a = 15.9712(18) A, b = 15.9253(19) A, c = 18.475(2) A, Pbca), a compound isostructural with 7, is synthesized by using cyclohexanol as a template. Thus, these cobalt(II) imidazolate polymers are reminiscent of the zeolite syntheses in that not only the same topological structure can be synthesized by using the different organic templates, but also different topological structures can be synthesized by using the same organic template.

Synthesis and Structure of Alkaline Earth Silicon Nitrides: BaSiN 2 , SrSiN 2 , and CaSiN 2

Abstract: The alkaline earth silicon nitrides AESiN2 (AE = Ca, Sr, Ba) are reported, synthesized as clear, colorless, single crystals from molten sodium at 900−1100 °C or, in the cases of BaSiN2 and SrSiN2, as white powders by reacting powdered intermetallics AESi with flowing anhydrous ammonia at 550−1000 °C. Structures were determined from single-crystal X-ray diffraction measurements at 150 K: BaSiN2 crystallizes in space group Cmca (No. 64) with a = 5.6046(1) A, b = 11.3605(3) A, c = 7.5851(2) A, and Z = 8. The structure consists of pairs of SiN4 tetrahedra edge-linked to form bow-tie-shaped Si2N6 dimers which share vertexes to form layers and has no analogue in oxide chemistry. SrSiN2 has a distorted form of this structure (SrSiN2: space group P21/c (No. 14), a = 5.9750(5) A, b = 7.2826(7) A, c = 5.4969(4) A, β = 113.496(4)°, Z = 4). The structure of CaSiN2 contains only vertex-sharing SiN4 tetrahedra, linked to form a three-dimensional stuffed-cristobalite type framework isostructural with KGaO2 (CaSiN2: s...

Functionalization of Polyoxometalates by a Negatively Charged Bridging Ligand: The Dimeric [(SiW11O39Ln)2(μ-CH3COO)2]12− (Ln = GdIII, YbIII) Complexes

Abstract: The possibility of coupling lacunary polyoxometalates through a cationic center present in the vacancy by negatively charged organic ligands is demonstrated for the first time by single-crystal X-ray diffraction. The structure of the dimeric K12[{Yb(α-SiW11O39)(H2O)}2(μ-CH3COO)2]·38H2O complex, where two acetato ligands connect the ytterbium centers in a (η2, μ-1,1) fashion, is reported. Using gadolinium instead of ytterbium, both the isostructural dimeric compound K12[{Gd(α-SiW11O39)(H2O)}2(μ-CH3COO)2]·38H2O and the mononuclear sandwich complex [Gd(SiW11O39)2]13− can be selectively isolated, depending on the synthetic conditions. The magnetic properties of the dimeric gadolinium complex are presented. The influence of the nature of the rare-earth metal on the final compound is further highlighted by the fact that when praseodymium is used as the rare-earth element, only the sandwich compound can be obtained. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Synthesis, crystal structure and magnetic properties of two-dimensional malonato-bridged cobalt(II) and nickel(II) compounds

Abstract: Two isostructural malonato-bridged complexes of formula {[M(H2O)2][M(mal)2(H2O)2]}n [M = Co(II) (1), Ni(II) (2); H2mal = malonic acid] have been synthesised and characterized by X-ray diffraction. Their structure consists of corrugated layers of trans-diaquabismalonatemetalate(II) and trans-diaquametal(II) units bridged by carboxylate–malonate groups in the anti–syn conformation. Two crystallographycally independent metal atoms occur in 1 and 2. The malonate anion acts simultaneously as a bidentate and bis-monodentate ligand. Variable-temperature (1.9–295 K) magnetic susceptibility measurements indicate the occurrence of weak antiferro- (1) and ferromagnetic (2) interactions between the cobalt(II) (1) and nickel(II) ions (2) through the anti–syn caboxylate–malonate bridge. A brief discussion on the structural diversity and crystal engineering possibilities of the malonate complexes with divalent first-row transition metal ions other than copper(II) is carried out.

Ortho‐Chalcogenostannates as Ligands: Syntheses, Crystal Structures, Electronic Properties, and Magnetism of Novel Compounds Containing Ternary Anionic Substructures [M4(μ4‐Se)(SnSe4)4]10− (M=Mn, Zn, Cd, Hg), ${{{\hfill 3\atop \hfill \infty }}}${[Hg4(μ4‐Se)(SnSe4)3]6−}, or ${{{\hfill 1\atop \hfill \infty }}}${[HgSnSe4]2−}

Abstract: By reaction of K 4 [SnSe 4 ].1.5-MeOH with CdCl 2 or Hg(OAc) 2 in water/methanol it was possible to prepare single crystals of four novel compounds that contain ternary anionic coordination oligomers and polymers: [Kio(H 2 O) 1 6 (MeOH) 0 . 5 ][M 4 (μ 4 -Se)(SnSe 4 ) 4 ] (4: M=Cd, 5: M=Hg), [K 6 (H 2 O) 3 ][Hg 4 (μ 4 -Se)(SnSe4) 3 ).MeOH (6), and K 2 [HgSnSe 4 ] (7), which were structurally characterized by single-crystal X-ray diffraction. The optical absorption properties of the isostructural compounds 4 and 5, as well as those of the recently reported Zn (2) and Mn (3) analogues, were studied by UV-visible spectroscopy. These investigations showed the quaternary phases to have relatively small optical gaps for their molecular size (2.2-2.6 eV), which are similar to the excitation energies that were observed for mesostructured solids of the respective combination of elements. According to DFT investigations on the ternary anions, an experimentally observed difference between the absorption behavior of the d 1 0 compounds 2, 4, and 5 and the open-shell d 5 compound 3 is in line with different characters of the frontier orbitals in the two cases. Both the calculations and a magnetic measurement on 3 demonstrated antiferromagnetic coupling between the μ 4 -Se-bridged Mn centers.

Syntheses, structures and properties of 1-ethyl-3-methylimidazolium salts of fluorocomplex anions.

Abstract: Fluoroacid–base reactions of a room-temperature ionic liquid, 1-ethyl-3-methylimidazolium fluorohydrogenate (EMIm(HF)2.3F, EMIm = 1-ethyl-3-methylimidazolium cation), and Lewis fluoroacids (BF3, PF5, AsF5, NbF5, TaF5 and WF6) give EMIm salts of the corresponding fluorocomplex anions, EMImBF4, EMImPF6, EMImAsF6, EMImNbF6, EMImTaF6 and EMImWF7, respectively. Attempts to prepare EMImVF6 by both the acid–base reaction of EMIm(HF)2.3F with VF5 and the metathesis of EMImCl with KVF6 failed due to the strong oxidizing power of the pentavalent vanadium, whereas EMImSbF6 was successfully prepared only by the metathesis of EMImCl and KSbF6. EMImBF4, EMImSbF6, EMImNbF6, EMImTaF6 and EMImWF7 are liquids at room temperature whereas EMImPF6 and EMImAsF6 melts at around 330 K. Raman spectra of the obtained salts showed the existence of the EMIm cation and corresponding fluorocomplex anions. IR spectroscopy revealed that strong hydrogen bonds are not observed in these salts. EMImAsF6 (mp 326 K) and EMImSbF6 (mp 283 K) are isostructural with the previously reported EMImPF6. The melting point of the hexafluorocomplex EMIm salt decreases with the increase of the size of the anion (PF6− < AsF6− < SbF6−

Crystal structures and thermoelectric properties of layered compounds in the ATe-Bi2Te3 (A = Ge, Sn, Pb) systems

Abstract: Single-crystal and powder x-ray diffraction studies of compounds in the nATe · mBi2Te3 (A = Ge, Sn, Pb) homologous series in the pseudobinary systems ATe–Bi2Te3 reveal a marked dissimilarity of the GeTe–Bi2Te3 system from SnTe–Bi2Te3 and PbTe–Bi2Te3. The GeTe–Bi2Te3 system contains, along with GeBi2Te4 (n/m = 1), GeTe-rich (n/m > 1) and Bi2Te3-rich (n/m < 1) members of the nGeTe · mBi2Te3 series. In contrast, the Sn and Pb systems contain only Bi2Te3-rich compounds (n/m < 1). This dissimilarity is interpreted in terms of the crystal structures of GeTe, SnTe, and PbTe. The thermoelectric properties of nPbTe · mBi2Te3 compounds are studied in a broad temperature range. The thermoelectric figures of merit of unoptimized n-type PbBi4Te7 and PbBi2Te4 are ZT= 0.5 and 0.4 at 600 and 650 K, respectively. Comparison of the thermoelectric properties of the isostructural 12-layer compounds GeBi4Te7, SnBi4Te7, and PbBi4Te7 indicates that the maximum in thermopower shifts to higher temperatures in going from the Ge to Sn and Pb compounds.

Supramolecular Recognition of Heteropairs of Lanthanide Ions: A Step toward Self-Assembled Bifunctional Probes

Abstract: Three unsymmetrical ditopic hexadentate ligands coded for the recognition of trivalent lanthanide ions have been synthesized, L(AB), L(AC), and L(BC), where A represents a benzimidazole-pyridine-benzimidazole coordination unit, B a benzimidazole-pyridine-carboxamide one, and C a benzimidazole-pyridine-carboxylic acid moiety. Under stoichiometric 2:3 (Ln:L) conditions, these ligands self-assemble with lanthanide ions to yield triple-stranded bimetallic helicates having a sizable stability in acetonitrile: log beta(23) values for Eu are equal to 23.9 +/- 0.5 (L(AB)), 23.3 +/- 0.7 (deprotonated L(AC)), and 29.8 +/- 0.5 (deprotonated L(BC)). The crystal structure of the EuEu helicate with L(AB) shows 9-coordinate metal ions and an HHH (H stands for head) configuration of the helically wrapped ligand strands. In the presence of equimolar quantities of Ln and Ln' ions, L(AB) displays a remarkable predisposition to form HHH-heterobimetallic edifices, as proved both in the solid state by the crystal structures of the LaEu, LaTb, PrEr, and PrLu helicates and in solution by NMR spectroscopy. In all cases, the benzimidazole-pyridine-carboxamide units of the three ligands are bound to the smaller lanthanide ion, a fact further ascertained by high-resolution luminescence data on LaEu and by (1)H NMR. Analysis of the lanthanide-induced (1)H NMR shifts and of the spin-lattice relaxation times of the [LnLu(L(AB))(3)](6+) series (Ln = Ce, Pr, Nd, Sm, Eu) demonstrates the isostructural nature of the complexes in solution and that the crystal structure of LaTb is a good model for the solution structure. The selectivity of L(AB) for heteropairs of Ln(III) ions increases with increasing difference in ionic radius, resulting in 70% of the heterobimetallic species for deltar(i) = 0.1 A and up to 90% for LaLu (deltar(i) = 0.18 A), and corresponding to delta(deltaG) in the range 3-10 kJ.mol(-)(1). The origins of this stabilization are discussed in terms of the donor properties of the coordinating units and of the preferential formation of HHH isomers.

Does Hydrogen Bonding Matter in Crystal Engineering? Crystal Structures of Salts of Isomeric Ions

Abstract: The preparation and structure determinations of the crystalline salts [3,3-H 2 bipy][PtCl 4 ] (2), [2,2'-H 2 bipy][PtCl 4 ] (3) and [1,4'-Hbipy] [PtCl 4 ] (4) and [3,3'-H 2 bipy][SbCl 5 ] (6) and [1,4'-Hbipy][SbCl 5 ] (8) are reported. In addition a redetermination of the structure of the metastable salt [4,4'-H 2 bipy][SbCl 5 ] (5b) in the corrected space group Phcm is described. These structures are compared to those of the known salt [4,4'-H 2 bipy][PtCl 4 ] (1), the stable triclinic form of [4.4'-H 2 bipy][SbCl 5 ] (5a) and [2,2'-H 2 bipy] [SbCl 5 ] (7). In the case of the salts of the rigid [PtCl 4 ] 2 - ion, structures 2, 3 and 4 are essentially isostructural despite the differing hydrogen-bonding capability of the cations. Similarly among the salts of [SbCl 5 ] 2 - ions, structures 7 and 8 are essentially isostructural. Structure 6 differs from these in having a differing pattern of aggregation of the [SbCl 5 ] 2 - ions to form polymeric rather than tetrameric units. It is evident that local hydrogen-bonding interactions, although significant, are not the only or even the decisive influence on the crystal structures formed by these salts. These observations are not in good accord with the heuristic "sticky tecton" or supramolecular synthon models for synthetic crystallography or crystal engineering.

Novel lanthanide coordination polymers with a flexible disulfoxide ligand, 1,2-bis(ethylsulfinyl)ethane: structures, stereochemistry, and the influences of counteranions on the framework formations.

Abstract: The reactions of meso-1,2-bis(ethylsulfinyl)ethane (meso-L) with Ln(ClO4)3 [Ln(NO3)3 or Ln(NCS)3] in MeOH and CHCl3 gave a series of new lanthanide coordination polymers, {[Ln(μ-meso-L)(rac-L)2(CH3OH)2](ClO4)3}n [Ln: La (1), Nd (2), Eu (3), Gd (4), Tb (5), Dy (6), and Yb (7)], [Yb(μ-meso-L)1.5(NO3)3]n (8), and [La(μ-meso-L)2.5(NCS)3]n (9). All the structures were established by single-crystal X-ray diffraction. Complexes 1−7 are isostructural with infinite single μ-chain structure, in which the L ligands take two kinds of coordination modes: bidentate chelating and bis-monodentate bridging. Six sulfur atoms of the sulfoxide groups around each LnIII center adopt alternatively the same R or S configuration in the chain. In addition, the configuration change of partial ligands occurred from the meso to the rac form when reacting with Ln(ClO4)3. To our knowledge, this is the first example of disulfoxide complexes with two kinds of coordination modes and three kinds of configurations (R,R, S,S, and R,S) occu...

Synthesis, structure, and characterization of two new layered mixed-metal phosphates, BaTeMO4(PO4) (M = Nb5+ or Ta5+.

Abstract: Two new isostructural mixed-metal phosphates, BaTeMO4(PO4) (M = Nb5+ or Ta5+), have been synthesized as bulk phase powders and single crystals by standard solid-state techniques using BaCO3, TeO2, Nb2O5 (or Ta2O5), and NH4H2PO4 as reagents. The materials have novel layered crystal structures consisting of [M5+O6/2]- corner-sharing octahedral chains that are connected to [Te4+O4/2]0 polyhedra and [P5+O2/1O2/2]- tetrahedra. The Ba2+ cations reside between the layers and maintain charge balance. The Te4+ cations are in asymmetric coordination environments attributable to their lone pairs. The Nb5+ distorts along the local C4 direction of its octahedron resulting in a “short−long−short−long” Nb−O−Nb bond motif. The Nb5+ cation displaces away from the oxide ligands that are bonded to Te4+ or P5+ cations, attributable to the structural rigidity of the TeO4 and PO4 polyhedra. Thus, the TeO4 and PO4 polyhedra support and reinforce the intraoctahedral distortion observed within the NbO6 octahedra. Infrared and Ram...

Dinitrogen activation by titanium sandwich complexes.

Abstract: The activation of dinitrogen by titanium sandwich complexes of the general form (η5-C5Me4R)2Ti (R = CHMe2, CMe3, SiMe3) has been systematically investigated. Low-temperature, in situ, solution infrared spectroscopy has allowed detection of monomeric bis-dinitrogen complexes of titanium that are isostructural with more familiar dicarbonyl derivatives. One example, (η5-C5Me4CHMe2)2Ti(N2)2, has also been characterized by X-ray diffraction and reveals weakly activated dinitrogen ligands. From the solution IR data, the relative azophilicity of the titanium sandwich complexes has been established and increases with smaller cyclopentadienyl substituents.

Four New Thioantimonates(III) with the General Formula [TM(tren)]Sb4S7 (TM = Mn, Fe, Co, Zn) with the Transition Metal as Part of a Thioantimonate(III) Network Synthesized under Solvothermal Conditions and Tuning of the Optical Band Gap by the Transition Metal Cation†

Abstract: Four new thioantimonate(III) compounds with the general formula [TM(tren)]Sb4S7, TM = Mn 1, Fe 2, Co 3 and Zn 4, were synthesized under solvothermal conditions by reacting elemental TM, Sb and S in an aqueous solution of tren (tren = tris(2-aminoethyl)amine). All compounds crystallize in the monoclinic space group P21/n with four formula units in the unit cell. Single crystal X-ray analyses of 1 [a = 8.008(2), b = 10.626(2), c = 25.991(5) A, β = 90.71(3)°, V = 2211.4(8) A3], 2 [a = 8.0030(2), b = 10.5619(2), c = 25.955(5) A, β = 90.809(3)°, V = 2193.69(8) A3], 3 [a = 7.962(2), b = 10.541(2), c = 25.897(5) A, β = 90.90(3)°, V = 2173.0(8) A3] and 4 [a = 7.978(2), b = 10.625(2), c = 25.901(5) A, β = 90.75(3)°, V = 2195.2(8) A3] reveal that the compounds are isostructural. The [Sb4S7]2- anions are composed of three SbS3 trigonal pyramids and one SbS4 unit as primary building units (PBU). The PBUs share common edges and corners to form semicubes (Sb3S4) which may be regarded as secondary building units (SBU). The SBUs and SbS3 pyramids are joined in an alternating fashion yielding the [Sb4S7-] anionic chain which is directed along [100]. Weaker Sb-S bonding interactions between neighbored chains lead to the formation of layers within the (001) plane which contain pockets that are occupied by the cations. The TM2+ ions are in a trigonal bipyramidal environment of four N atoms of the tren ligand and one S atom of the thioantimonate(III) anion. The optical band gaps depend on the TM2+ ion and amount to 3.11 eV for 1, 2.04 eV for 2, 2.45 eV for 3, and 2.60 eV for 4.

Heavy-metal aromatic rings: Cyclopentadienyl anion analogues Sn56- and Pb56- in the zintl phases Na8BaPb6, Na8BaSn6, and Na8EuSn6

Abstract: The title compounds were prepared by direct reactions of the corresponding elements at high temperature. They are isostructural with each other (monoclinic, P21/m, Z = 2; Na8BaPb6, a = 13.116(4), b = 5.351(1), and c = 16.166(5) A, β = 108.07(2)°; Na8BaSn6, a = 12.897(4), b = 5.362(1), and c = 16.826(5) A, β = 108.19(2)°; Na8EuSn6, a = 12.912(2), b = 5.220(1), and c = 15.721(2) A, β = 108.09(1)°) and contain isolated, flat, and aromatic pentagonal rings of Sn56- and Pb56- as well as isolated anions of Sn4- and Pb4-. According to four-probe conductivity measurements, the tin compounds, Na8BaSn6 and Na8EuSn6, are semiconducting with band gaps of 0.11 and 0.09 eV, respectively, and are therefore electronically balanced. Magnetic measurements show that Na8BaSn6 is diamagnetic while Na8EuSn6 is paramagnetic and undergoes two transitions at low temperatures.

Chiral templating activity of tris(bipyridine)ruthenium(II) cation in the design of three-dimensional (3D) optically active oxalate-bridged {[Ru(bpy)3][Cu2xNi2(1-x)(C2O4)3]}n (0 ≤ x ≤ 1; bpy = 2,2'-bipyridine): Structural, optical, and magnetic studies

Abstract: Three-dimensional oxalate-based {[Ru(bpy)3][Cu2xNi2(1-x)(ox)3]}n (0≤ x ≤ 1, ox = C2O42-, bpy = 2,2‘bipyridine) were synthesized. The structure was determined for x = 1 by X-ray diffraction on single crystal. The compound crystallizes in the cubic space group P4132. It shows a three-dimensional 10-gon 3-connected (10,3) anionic network where copper(II) has an unusual tris(bischelated) environment. X-ray powder diffraction patterns and their Rietveld refinement show that all the compounds along the series are isostructural and single-phased. According to X-ray absorption spectroscopy, copper(II) and nickel(II) have an octahedral environment, respectively elongated and trigonally distorted. As shown by natural circular dichroism, the optically active forms of {[Ru(bpy)3][CuxNi2(1-x)(ox)3]}n are obtained starting from resolved Δ- or Λ-[Ru(bpy)3]2+. The Curie−Weiss temperatures range between −55 (x = 1) and −150 K (x = 0). The antiferromagnetic exchange interaction thus decreases when the copper contents incre...

Supramolecular architecture of new lanthanide coordination polymers of 2-aminoterephthalic acid and 1,10-phenanthroline

Abstract: This paper presents five new lanthanide coordination polymers with 2-aminoterephthalic acid (H2atpt) and 1,10-phenanthroline (phen), [Ln(atpt)1.5(phen)(H2O)]n [Ln = La (1); Eu (2)], [Ln2(atpt)3(phen)2(H2O)]n [Ln = Tb (3); Er (4)] and [Yb2(OH)(atpt)2.5(phen)2]n·1.75nH2O (5), prepared by hydrothermal reactions and structurally characterized. 1 and 2 are isostructural, in which all the Ln3+ ions are eight-coordinated. 3 and 4 are also isostructural and have two types of lanthanides; Ln(1) (Ln = Tb, Er) is seven-coordinated and Ln(2) (Ln = Tb, Er) is eight-coordinated in the asymmetric unit. 1–4 are two-dimensional rhombus-like grids constructed by bridging atpt ligands, and further form 3-D supramolecular architectures via hydrogen bonds and π–π stacks between phen molecules. Complex 5, in which there are two eight-coordinated Yb3+ ions linked by one hydroxyl group and one atpt ligand in the asymmetric unit, exhibits an interpenetrated 3-D network with a brick structure. In 1–4 one atpt ligand is coordinated to three or four Ln3+ ions (Ln = La, Eu, Tb, Er) in bridging modes and in 5 one atpt ligand is coordinated to two or three Yb3+ ions by double chelating or chelating-bridging mode. The high-resolution emission spectrum of 2 shows only one Eu3+ ion site in 2, which is in agreement with the results of the X-ray diffraction. The thermal stabilities of the supramolecular compounds 2, 4 and 5 show that the presence of amino groups induces formation of hydrogen bonds that are responsible for the increase in the thermal stability.

Incommensurate nature of the multilayered molecular ferromagnetic metals based on bis(ethylenedithio)tetrathiafulvalene and bimetallic oxalate complexes.

Abstract: The salt [ET]x[MnRh(ox)3]·CH2Cl2 (x = 2.526(1)) has been obtained and characterized. This paramagnetic metal is essentially isostructural to the ferromagnetic metal [ET]y[MnCr(ox)3]·CH2Cl2 (y ≈ 3) and provides a definite answer on the origin of the structural disorder present on such systems. As in the ferromagnetic analogue, this material shows high electrical conductivity at room temperature (13 S·cm-1) and metallic behavior.

A Family of Mn16 Single-Molecule Magnets from a Reductive Aggregation Route

Abstract: The synthesis and magnetic properties of three isostructural hexadecametallic manganese clusters [Mn16O16(OMe)6(O2CCH2Ph)16(MeOH)6] (1), [Mn16O16(OMe)6(O2CCH2Cl)16(MeOH)6] (2), and [Mn16O16(OMe)6(O2CCH2Br)16(MeOH)6] (3) are reported. The complexes were prepared by a reductive aggregation reaction involving phenylacetic acid, chloroacetic acid or bromoacetic acid, and NBun4MnO4 in MeOH. Complex 1 crystallizes in the monoclinic space group C2/c and consists of 6 MnIV and 10 MnIII ions held together by 14 μ3-O2-, 2 μ-O2-, 4 μ-MeO-, and 2 μ-O2CCH2Ph- groups. The remaining 14 μ-O2CCH2Ph- ligands, 2 μ-MeO- groups, and 6 terminal MeOH molecules constitute the peripheral ligation in the complex. Variable-temperature, solid-state dc magnetic susceptibility measurements on 1−3 in the temperature range 5.0−300 K reveal that all three complexes are dominated by intramolecular antiferromagnetic exchange interactions. Low-lying excited states preclude an exact determination of the spin ground state for 1−3 by magnetiza...

Asymmetric cationic coordination environments in new oxide materials: synthesis and characterization of Pb(4)Te(6)M(10)O(41) (M = Nb(5+) or Ta(5+)).

Abstract: Two new isostructural tellurites, Pb4Te6M10O41 (M = Nb5+ or Ta5+), have been synthesized by standard solid-state techniques using PbO, Nb2O5 (or Ta2O5), and TeO2 as reagents. The structures of Pb4Te6Nb10O41 and Pb4Te6Ta10O41 were determined by single-crystal and powder X-ray diffraction. The materials exhibit a three-dimensional framework consisting of layers of corner-shared NbO6 octahedra connected by TeO3 and PbO6 polyhedra. The Nb5+, Te4+, and Pb2+ cations are in asymmetric coordination environments attributable to second-order Jahn−Teller effects. The Nb5+ cations undergo an intraoctahedral distortion either toward a face or a corner, whereas the Te4+ and Pb2+ cations are in distorted environments attributable to their lone pair. In addition, the TeO3 polyhedra strongly influence the direction of the Nb5+ intraoctahedral distortion. Infrared and Raman spectroscopy, thermogravimetric analysis, and dielectric measurements are also presented. Crystal data: Pb4Te6Nb10O41, monoclinic, space group C2/m (N...

Synthesis, structure, and magnetic properties of amine-templated open-framework nickel(II) sulfates.

Abstract: Two organically templated nickel sulfates of the compositions [C4N2H12][Ni3F2(SO4)3(H2O)2] (I) and [C4N2H12][Ni2F4(SO4)H2O] (II) with open architectures have been synthesized under hydro/solvothermal conditions in the presence of piperazine. I has a layered structure formed by sinusoidal chains comprising hexameric units, whereas II has a three-dimensional structure with 10-membered channels. The layered Ni(II) sulfate, I, is ferrimagnetic, exhibiting hysteresis at low temperatures. The three-dimensional Ni(II) sulfate, II, is essentially paramagnetic. We have also obtained layered compounds isostructural with I containing other amines.

Syntheses, Thermal Stability, and Structure Determination of the Novel Isostructural RBa3B9O18 (R = Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb)

Abstract: A novel borate compound YBa3B9O18 has crystallized in a melt of BaYB9O16. Single-crystal X-ray diffraction measurements reveal that YBa3B9O18 adopts a hexagonal space group P(3 m with cell parameters of a = 7.1761(6) Angstrom and c = 16.9657(6) Angstrom. The structure is made up of the planar B3O6 groups parallel to each other along the (001) direction, regular YO6 octahedra, and irregular BaO6 and BaO9 polyhedra to form an analogue structure of beta-BaB2O4. A series of isostructural borate compounds RBa3B9O18 (R = Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) were prepared by powder solid-state reactions. The DTA and TGA curves of YBaB9O16 show an obvious weight loss at about 955 degreesC associated with a decomposition into YBO3, B2O3, and YBa3B9O18 due to its incongruent melting behavior. The DTA and TGA curves of YBa3B9O18 show that it is chemically stable and a congruent melting compound. A comparison of the structures of YBa3B9O18 and beta-BaB2O4 is presented.

Synthesis and structure of layered compounds in the PbTe-Bi2Te3 and PbTe-Sb2Te3 systems

Abstract: —A number of tetradymite-like layered compounds in the PbTe−Bi2Te3 and PbTe−Sb2Te3 systems were prepared by a vertical Bridgman process, and their crystal structures were investigated by x-ray diffraction using single-crystal cleaved specimens. The atomic positional parameters and bond distances in PbBi4Te7 were determined. In the pseudobinary system PbTe−Sb2Te3, two new compounds were identified, PbSb2Te4 and PbSb4Te7, isostructural with PbBi2Te4 and PbBi4Te7, respectively. The positional parameters, site occupancies, and bond distances in the structure of PbSb2Te4 were determined. The room-temperature thermoelectric power of the grown ingots was measured along their length. All of the Sb compounds studied were found to be p-type, in contrast to the compounds of the PbTe−Bi2Te3 system.

Hydrothermal Syntheses, Structures, and Properties of Three 3‐D Lanthanide Coordination Polymers that Form 1‐D Channels

Abstract: We report the hydrothermal synthesis and crystal structure of isostructural lanthanide coordination polymers [Ln2(NDC)3(phen)2]·H2NDC [Ln = Tb (1), Ho (2) and Yb (3)] that feature 2,6-naphthalenedicarboxylate (NDC) and 1,10-phenanthroline (phen) ligands. The NDC ligands bridge the lanthanide ions in two different modes to form a 3-D porous framework that accommodates large, neutral 2,6-naphthalenedicarboxylic acid molecules as guests in the channels, stabilized through O−H···O hydrogen bonds to the NDC ligand. The effective dimension of the channel is ca. 6.0 × 8.2 A. Thermogravimetric analysis shows that complex 2 remains stable up to 330 °C, which we confirmed also by powder X-ray diffraction analyses. The framework collapsed upon the loss of the coordinating phen molecules. The Tb complex shows strong evidence of ferromagnetic coupling interactions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Molecular clips form isostructural dimeric aggregates from benzene to water.

Abstract: We report the synthesis and characterization of eight C-shaped methylene-bridged glycoluril dimers (1−8) bearing hydrogen-bonding amide groups on their aromatic rings. Compounds 1−6 undergo tight dimerization in CDCl3 solution (Ks > 9 × 105 M-1); binary mixtures of 1−7 form mixtures of homodimers and heterodimers in moderately selective dimerization processes (0.23 ≤ Keq ≤ 768; 0.253 ≤ χAB < 0.933). The high affinity formation of 1·1−6·6 is due to the commensurate nature of the geometrical constraints imposed by the π−π interactions and only two hydrogen bonds. The differential response of the strengths of the π−π interactions and H-bonds of 2·2 to changes in solvent polarityfrom C6D6 to D2Oresults in the formation of a solvent-independent isostructural aggregate that exhibits high affinity dimerization across the full range of solvents.