Showing papers on "Isostructural published in 2007"
TL;DR: It is proved that 3,5-pyrazoledicarboxylic acid may be used as an effective bridging ligand to assemble lanthanide-based coordination polymers and the structure variation from the 3D porous framework to the 2D double-decker to the2D monolayer is attributed to the lanthanides contraction effect.
Abstract: 3,5-Pyrazoledicarboxylic acid (H3L) reacts with nitrate salts of lanthanide(III) (Ln = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er) under hydrothermal conditions to form a series of lanthanide polymers 1−9. These nine polymers have the same crystal system of monoclinic, but they exhibit three different kinds of metal−organic framework structures. The complexes {[Ln2(HL)3(H2O)4]·2H2O}n (Ln = Pr (1), Nd (2), and Sm (3)) were isostructural and exhibited porous 3D frameworks with a Cc space group. The complexes {[Ln2(HL)3(H2O)3]·3H2O}n (Ln = Eu (4), Gd (5), and Tb (6)) were isostructural and built 2D double-decker (2DD) frameworks with a P21/c space group. The complexes {[Ln(HL)(H2L)(H2O)2]}n ((Ln = Dy (7), Ho (8), and Er (9)) were also isostructural and formed 2D monolayer (2DM) frameworks with a P21/n space group. The structure variation from the 3D porous framework to the 2D double-decker to the 2D monolayer is attributed to the lanthanide contraction effect. Notably, six new coordination modes of 3,5-pyrazoled...
271 citations
TL;DR: A complete, isostructural series of complexes with La-Lu (except Pm) with the ligand TREN-1,2-HOIQO has been synthesized and structurally characterized by means of single-crystal X-ray analysis, providing a significant advance for the prediction and rationalization of the geometric features of the corresponding lanthanide complexes.
Abstract: A complete, isostructural series of complexes with La−Lu (except Pm) with the ligand TREN-1,2-HOIQO has been synthesized and structurally characterized by means of single-crystal X-ray analysis. All complexes are 1D-polymeric species in the solid state, with the lanthanide being in an eight-coordinate, distorted trigonal-dodecahedral environment with a donor set of eight unique oxygen atoms. This series constitutes the first complete set of isostructural complexes from La−Lu (without Pm) with a ligand of denticity greater than two. The geometric arrangement of the chelating moieties slightly deviates across the lanthanide series, as analyzed by a shape parameter metric based on the comparison of the dihedral angles along all edges of the coordination polyhedron. The apparent lanthanide contraction in the individual Ln−O bond lengths deviates considerably from the expected quadratic decrease that was found previously in a number of complexes with ligands of low denticity. The sum of all bond lengths around...
231 citations
TL;DR: The investigation of compound 5 by these methods and by IR spectroscopy indicates that cyanide linkage isomerism occurs during cluster formation, and Mössbauer spectra collected in the presence of a high applied field have allowed, for the first time, the direct experimental observation of uncompensated spin density at diamagnetic metal ions that bridge paramagneticMetal ions.
Abstract: Pentanuclear, cyanide-bridged clusters [M(tmphen)2]3[M‘(CN)6]2 (M/M‘ = Zn/Cr (1), Zn/Fe (2), Fe/Fe (3), Fe/Co (4), and Fe/Cr (5); tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline) were prepared by combining [M‘III(CN)6]3- anions with mononuclear complexes of MII ions with two capping tmphen ligands. The clusters consist of a trigonal bipyramidal (TBP) core with three MII ions in the equatorial positions and two M‘III ions in the axial positions. Compounds 1−4 are isostructural and crystallize in the monoclinic space group P21/c. Complex 5 crystallizes in the enantiomorphic space group P3221. The magnetic properties of compounds 1 and 2 reflect the contributions of the individual [CrIII(CN)6]3- and [FeIII(CN)6]3- ions. The FeII ions in compounds 3 and 4 exhibit a gradual, temperature-induced spin transition between high spin (HS) and low spin (LS), as determined by the combination of Mossbauer spectroscopy, magnetic measurements, and single-crystal X-ray studies. The investigation of compound 5 by these me...
182 citations
TL;DR: In this paper, the phase relations in the MnO-SiO2-Li4SiO4 subsystem have been investigated by X-ray diffraction after solid-state reactions in hydrogen at 950-1150°C.
160 citations
TL;DR: In this article, a theoretical study of the electronic band structure, density of states, dielectric function and absorption coefficient of isostructural BaSi2, BaGe2 and SrGe2 compounds was performed by means of different ab initio methods.
Abstract: We have performed a theoretical study of the electronic band structure, density of states, dielectric function and absorption coefficient of isostructural BaSi2, BaGe2 and SrGe2 compounds by means of different ab initio methods. All materials are found to be indirect band-gap semiconductors displaying almost equal dispersion of bands close to the gap region. The energy gaps of 0.83, 0.57 and 0.44 eV are estimated for BaSi2, BaGe2 and SrGe2, respectively. Analysis of the absorption coefficient of BaSi2 in comparison with data for other semiconducting silicides indicates its prospects for a solar cell application. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
144 citations
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TL;DR: The coordination environment of the hydrated Cm3+ ion is probed both in the solid state and in solution, and the increase in splitting of the Cm-water distances in the first coordination sphere is discussed in terms of its potential relevance to the previously observed decrease in coordinating waters with decreasing ionic radius about the f-ion in solution.
Abstract: The coordination environment of the hydrated Cm3+ ion is probed both in the solid state and in solution. The analysis of single-crystal X-ray diffraction data from [Cm(H2O)9](CF3SO3)3 determines that the Cm species is surrounded by nine coordinating waters with a tricapped-trigonal-prismatic geometry involving six short Cm-O distances at 2.453(1) A and three longer Cm-O distances at 2.545(1) A. The Cm nona-aqua triflate is isostructural with the series of lanthanide and actinide [R(H2O)9](CF3SO3)3 (R=La-Lu, Pu) compounds. A similar nona-aqua geometry is seen for the coordination environment of Cm in aqueous solution, as probed by high-energy X-ray scattering and extended X-ray absorption fine structure spectroscopy, although the splitting in the first coordination shell is increased from 0.092(2) in the solid to 0.16(2) A in solution. This increase in splitting of the Cm-water distances in the first coordination sphere is discussed in terms of its potential relevance to the previously observed decrease in coordinating waters with decreasing ionic radius about the f-ion in solution.
128 citations
TL;DR: In this paper, the X-ray structure analyses showed three kinds of 1D chain structures, and there are intramolecular π−π stacking interactions between the pyridyl ring planes.
Abstract: Nine one-dimensional (1D) lanthanide(III) coordination polymers with the formulas {[La(pta)(H2O)4]·2H2O}n (1), {[Ln(pta)(H2O)5]·4H2O}n [Ln = Sm (2), Eu (3), Tb (4), Ho (5)], and {[Ln(pta)(H2O)3]·4H2O}n [Ln = Dy (6), Er (7), Tm (8), Yb (9)] (H3pta = 2,4,6-pyridinetricarboxylic acid) have been synthesized by reacting the corresponding rare earth salts with H3pta at room temperature. The X-ray structure analyses show three kinds of 1D chain structures. Complexes 2−5 and 6−9 are isostructural, respectively. Complex 1 crystallized in the triclinic with P1 space group, 2−5 crystallized in the orthorhombic with Pna21 space group and 6−9 crystallized in the monoclinic with P21/c space group. In the three kinds of structures, H3pta displays two different coordination modes, and there are intramolecular π−π stacking interactions between the pyridyl ring planes. The complexes of Sm(III), Eu(III), Tb(III), and Dy(III) exhibit the corresponding characteristic luminescence in the visible region at an excitation of 305 ...
125 citations
TL;DR: In this paper, four cationic spacer-filled 3D transition metal supramolecular frameworks from N,N,N', N'''N'',N' 'N' -tris(carboxymethyl)-1,3,5- benzenetricarboxamide (L) have been synthesized hydrothermally.
Abstract: Four novel cationic spacer-filled 3D transition metal supramolecular frameworks from N,N‘,N‘ ‘-tris(carboxymethyl)-1,3,5- benzenetricarboxamide (L), {[ML(H2O)3]2[M(H2O)6](H2O)3}n (M = Zn, 1; Mn, 2; Ni, 3; Co, 4), have been synthesized hydrothermally. X-ray single-crystal diffraction studies confirm that these complexes are isostructural and crystallize in the hexagonal crystal system, with the space group being P31c. Each metal ion coordinates to three ligands and each ligand L bridges three metal ions as well, resulting in an infinite 2D anionic (6, 3) layer with large honeycomblike cavities. Interestingly, two adjacent layers are staggered in such a way that non-interepenetrating double-layer structures are formed. Such double layers are separated by the layer of hexaqua−metal cations through O−H···O hydrogen bonds between the −CONH− groups and the coordinated aqua molecules. Four complexes could be considered as dynamic molecular solids and exhibit interesting water-induced reversible crystal-to-amorp...
107 citations
TL;DR: In this paper, a series of heterometallic lanthanide(III)−copper(I) coordination polymers Ln2(bdc) 2(ina)2(H2O)2Cu·X (Hina = isonicotinic acid; H2bdc = 1,2-benzenedicarboxylic acid; Ln = Eu (1), Sm (2), Nd (3), X = ClO4-; Lln = Nd(4), Nc (5,6), X
Abstract: A new series of heterometallic lanthanide(III)−copper(I) coordination polymers Ln2(bdc)2(ina)2(H2O)2Cu·X (Hina = isonicotinic acid; H2bdc = 1,2-benzenedicarboxylic acid; Ln = Eu (1), Sm (2), Nd (3), X = ClO4-; Ln = Nd (4), X = Cl-) have been hydrothermally synthesized in the presence/absence of HClO4. Both compounds are isostructural and contained two distinct units of 2D Ln−bdc layers and linear [Cu(ina)2]-. The linear [Cu(ina)2]- complexes act as pillars and further link the Ln−bdc layers resulting in four heterometallic metal−organic frameworks, which represent the first pillared-layer 3d−4f framework with two distinct types of channels along the b and c axes. The compounds can be specified by the Schlafli symbol (47·63)(47·68) as a novel 3D (5,6)-connected net. Furthermore, the IR, TGA, PXRD, and UV−vis spectral and luminescent properties of 1−4 were also studied.
104 citations
TL;DR: The N-heterocyclic carbene (NHC) precursor 3,5-bis((N-methylimidazoliumyl)methyl)pyrazole bis(hexafluorophosphate) (H3L(PF6)2) reacted with Ag2O to afford the silver complex [Ag4L2]-PF6]2·0.5Et2O (5) as mentioned in this paper.
102 citations
TL;DR: In this article, two two-dimensional and one three-dimensional coordination polymers [Ni(HTTG)(H2O)2]n (1), [Co(H 2 O 2 )n (2), and [Cd(HTG)]n (3) have been hydrothermally synthesized by self-assembly of an unexplored tripodal ligand H3TTG and corresponding metal salts.
Abstract: Two novel two-dimensional (2D) and one three-dimensional (3D) coordination polymers[Ni(HTTG)(H2O)2]n (1), [Co(HTTG)(H2O)2]n (2), and [Cd(HTTG)]n (3)have been hydrothermally synthesized by self-assembly of an unexplored tripodal ligand H3TTG (N,N‘,N‘ ‘-1,3,5-triazine-2,4,6-triyltris-glycine) and corresponding metal salts. X-ray diffraction analysis reveals that the three polymers exhibit novel frameworks due to diverse coordination conformations and different acid forms of the flexible tricaboxylate ligands. The isostructural complexes 1 and 2 possess 2D frameworks with M(H2O)2(CO2)2 chains bridged by the ligands, and the resulting 3D networks were extended through R22(8) hydrogen bonds between the undeprotonated carboxylate groups and the triazine rings as well as π···π interactions between the triazine rings. Complex 3 shows a 3D interpenetrating compact network with inorganic Cd2O2 chains interconnected by the flexible organic ligands. Topological analysis indicates that in all three complexes the tripo...
TL;DR: The anions and the pH are believed to play key roles in directing the formation of a particular structure, and four types of Ln-notp compounds are studied.
Abstract: Reactions of 1,4,7-triazacyclononane-1,4,7-triyl-tris(methylenephosphonic acid) [notpH(6), C(9)H(18)N(3)(PO(3)H(2))3] with different lanthanide salts result in four types of Ln-notp compounds: [Ln{C(9)H(20)N(3)(PO(3)H)(2)(PO(3))}(NO(3))(H(2)O)].4H2O (1), [Ln = Eu (1 Eu), Gd (1 Gd), Tb (1 Tb)], [Ln{C(9)H(20)N(3)(PO(3)H)(2)(PO(3))}(H2O)]Cl.3H2O (2) [Ln = Eu (2 Eu), Gd (2 Gd), Tb (2 Tb)], [Ln{C(9)H(20)N(3)(PO(3)H)(2)(PO(3))}(H2O)]ClO4.8H2O, (3) [Ln = Eu (3 Eu), Gd (3 Gd)], and [Ln{C(9)H(20)N(3)(PO(3)H)(2)(PO(3))}(H2O)]ClO4.3H2O (4), [Ln = Gd (4 Gd), Tb (4 Tb)]. Compounds within each type are isostructural. In compounds 1, dimers of {Ln2(notpH4)2(NO3)2(H2O)2} are found, in which the two lanthanide atoms are connected by two pairs of O-P-O and one pair of mu-O bridges. The NO3- ion serves as a bidentate terminal ligand. Compounds 2 contain similar dimeric units of {Ln2(notpH4)2(H2O)2} that are further connected by a pair of O-P-O bridges into an alternating chain. The Cl- ions are involved in the interchain hydrogen-bonding networks. A similar chain structure is also found in compounds 3; in this case, however, the chains are linked by ClO4- counterions through hydrogen-bonding interactions, forming an undulating layer in the (011) plane. These layers are fused through hydrogen-bonding interactions, leading to a three-dimensional supramolecular network with large channels in the [100] direction. Compounds 4 show an interesting brick-wall-like layer structure in which the neighboring lanthanide atoms are connected by a pair of O-P-O bridges. The ClO4- counterions and the lattice water molecules are between the layers. In all compounds the triazamacrocyclic nitrogen atoms are not coordinated to the Ln(III) ions. The anions and the pH are believed to play key roles in directing the formation of a particular structure. The fluorescence spectroscopic properties of the Eu and Tb compounds, magnetic properties of the Gd compounds, and the catalytic properties of 4 Gd were also studied.
TL;DR: In this paper, three 3D Ln−M heterometallic coordination polymers, [Nd(H2O)2 (CuI)2(Nic)3] and [LnCu(inic) 2(ox)] have been synthesized under hydrothermal conditions by using linear multifunctional ligands with different geometries.
Abstract: By using linear multifunctional ligands with different geometries, three novel three-dimensional (3D) Ln−M heterometallic coordination polymers, [Nd(H2O)2(CuI)2(nic)3]·H2O (1) (Hnic = nicotinic acid) and [LnCu(inic)2(ox)]·H2O [Ln = Nd (2), Eu (3); Hinic = isonicotinic acid, H2ox = oxalic acid], have been synthesized under hydrothermal conditions. Compound 1 exhibits a novel 3D coordination framework constructed by Cu4I4 clusters, Nd centers, and nic ligands. Our present work represents the first example of 3D Ln−M heterometallic coordination framework incorporating discrete cubane transition metal clusters covalently bonded to lanthanide centers through linear ligands. An unusual chemical rearrangement from Hinic to ox occurs in the formation of 2 and 3. Compounds 2 and 3 are isostructural and possess the first 3D coordination framework based on the linkage of two-dimensional layers constructed by tetranuclear Ln2Cu2 clusters and inic ligands. Furthermore, the luminescent properties of 3 were studied.
TL;DR: In this article, a multiferroic perovskite, called Bi(Fe1∕2Cr1 ∕2)O3, is prepared in a bulk form by high pressure solid-state synthesis.
Abstract: Bi(Fe1∕2Cr1∕2)O3, a recently proposed candidate multiferroic perovskite, is prepared in a bulk form by high pressure solid-state synthesis. The material is isostructural with polar BiFeO3 but is paramagnetic at room temperature due to disorder of the Fe3+ and Cr3+ cations on the B site. Mossbauer and magnetization measurements show a transition to a cooperative magnetic state below 130K.
TL;DR: Two novel 3D heterometallic coordination polymers, Ln(4)(mu(3)-OH)(2)Cu(6)I(5)(IN)(8)(OAc)(3) (HIN = isonicotinic acid, HOAc = acetic acid), have been synthesized under hydrothermal conditions and characterized by elemental, infrared, and thermogravimetric analyses and single-crystal X-ray diffraction.
Abstract: Two novel 3D heterometallic coordination polymers, Ln4(μ3-OH)2Cu6I5(IN)8(OAc)3 (Ln = Nd (1), Pr (2); HIN = isonicotinic acid, HOAc = acetic acid), have been synthesized under hydrothermal conditions and characterized by elemental, infrared, and thermogravimetric analyses and single-crystal X-ray diffraction. Both compounds are isostructural and crystallize in the monoclinic system, space group P21/c. Both polymers are constructed from 2D lanthanide-cluster polymers based on the {Ln16} wheel-cluster and 1D copper-cluster polymers based on the {Cu6I5} cluster, which represent the first examples of 3D coordination frameworks created by using a combination of two different types of metal-cluster polymer units, namely, a high-nuclearity lanthanide-cluster polymer and a transition-metal-cluster polymer.
TL;DR: A pair of isostructural bis-selenathiazolyl and bis-diselenazolyl radical conductors display weak (spin-canted) ferromagnetism with Tc values of 18 K and 27 K respectively.
TL;DR: In this paper, the reaction of 2-(1-imidazole)-1-hydroxyl-1,1'-ethylidenediphosphonic acid (ImhedpH(4)) and cobalt or nickel salts under hydrothermal conditions lead to four new metal phosphonates with two types of structures: M-3(ImhedPH)(2)(H2O)(4)center dot 2H(2)O [M = Co(II) (1) and Ni(II)) (2) (2)] and M-
Abstract: Reactions of 2-(1-imidazole)-1-hydroxyl-1,1'-ethylidenediphosphonic acid (ImhedpH(4)) and cobalt or nickel salts under hydrothermal conditions lead to four new metal phosphonates with two types of structures: M-3(ImhedpH)(2)(H2O)(4)center dot 2H(2)O [M = Co(II) (1) and Ni(II) (2)] and M(ImhedpH(3))(2)(H2O)(2) [M = Co(II) (3) and Ni(II) (4)]. Compounds 1 and 2 are isostructural and show a layered structure made up of M-3(ImhedpH)(2)(H2O)(4) trimer units. These trimers are connected by edge-sharing of the {Co(2)O-6} octahedra, forming an undulating chain. The adjacent chains are fused through the coordination of the phosphonate oxygen atom from one chain to the Co(2) atom of the other, thus generating a two-dimensional layer containing 4-, 8-, and 16-membered rings. The imidazole groups are grafted on the two sides of the layer. Compounds 3 and 4 are also isostructural and show a mononuclear structure with extensive hydrogen bond interactions. Magnetic measurements reveal that both 1 and 2 exhibit canted antiferromagnetism at 2.6 and 5.0 K, respectively. Below these temperatures, slow relaxation is observed from the ac susceptibility measurements corresponding to the spin-glass-like behaviors.
TL;DR: The polymeric coordination compound of formula [Tm(hfac)3(NITPhOPh)]∞ has been synthesized and found to belong to the only reported family of isostructural Single Chain Magnets.
TL;DR: Density functional calculations have been used to explain the magnetic coupling in 2.H2O and both compounds exhibit antiferromagnetic interactions between metal ions through the pyrimidine-2-carboxylate bridging ligand.
Abstract: The hydrothermal reaction of 2-cyanopyrimidine and either CoCl2.6H2O or FeCl2.4H2O affords 2D isostructural coordination polymers [M2(micro-pymca)3]OH.H2O ((M = CoII (1) and FeII (2) pymca = pyrimidine-2-carboxylato). The bisdidentate ligand (pymca) that can be considered an intermediate between bipyrimidine and oxalato is generated in situ from the hydrolysis of 2-cyanopyrimidine. The structure of 1 and 2 consists of heterochiral (6,3) honeycomb layers, crystal water molecules, and OH- anions, the latter playing a template and balancing charge role in the structure. Both compounds exhibit antiferromagnetic interactions between metal ions through the pyrimidine-2-carboxylate bridging ligand. Compound 1 is a spin-canted antiferromagnet leading to weak ferromagnetism at Tc < 10 K with a coercitive field of 580 Oe, whereas compound 2 is an antiferromagnet with TN = 21 K. Fit of the variable-temperature magnetic susceptibility data of 2 to the empirical equation for a regular honeycomb with S = 1 derived from Monte Carlo simulations leads to the following parameters: J = -4.57(2) cm-1 and g = 2.300(4). Density functional calculations have been used to explain the magnetic coupling in 2.
TL;DR: Three isostructural disk-like heptanuclear FeIII compounds of the general formula [FeIII7(μ3-O)3(L)3 (μ-O2CCMe3)6(η1-O 2CCMe 3) 3(H2O) 3], where L represents a di- or triethanolamine moiety, display a th...
Abstract: Three isostructural disklike heptanuclear FeIII compounds of the general formula [FeIII7(μ3-O)3(L)3(μ-O2CCMe3)6(η1-O2CCMe3)3(H2O)3], where L represents a di- or triethanolamine moiety, display a th...
TL;DR: In this paper, the crystal structure of osmium nitride is shown to be isostructural to marcasite, and a comparison between the formation energies of OsN2 and PtN2 explains the similar thermodynamic conditions of formation reported experimentally for the two compounds.
Abstract: Osmium nitride belongs to a family of nitrides synthesized recently at high pressures from their parent elements. Here we show, based on first-principles calculations, that the crystal structure of osmium nitride is isostructural to marcasite. Excellent agreement is obtained between the authors’ results and x-ray, Raman, and compressibility measurements. In the OsN2 marcasite structure single-bonded N2 units occupy the interstitial sites of the Os close-packed lattice, giving rise to a metallic compound. A comparison between the formation energies of OsN2 and PtN2 explains the similar thermodynamic conditions of formation reported experimentally for the two compounds.
TL;DR: A series of layered lanthanide coordination frameworks have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction as mentioned in this paper, which display identical crystal system (triclinic) and space group (P).
Abstract: A series of layered lanthanide coordination frameworks [Ln4(NIPH)6(H2O)4]·(4,4′-bipy) [Ln = La (1), Pr (2)], [La(NIPH)2(H2O)2]·0.5(4,4′-H2bipy) (3), Ln(NIPH)2(H2O)2]·0.5(4,4′-H2bipy)·2H2O [Ln =Pr (4), Nd (5)], and [Ln(NIPH)2]·0.5(4,4′-H2bipy) [Ln = Sm (6), Eu (7), Tb (8), Ho (9), Yb (10)] (NIPH = 5-nitroisophthalate and 4,4′-bipy = 4,4′-bipyridine) have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction. All the coordination frameworks display identical crystal system (triclinic) and space group (P). Compounds 1 and 2 are isostructural, their coordination sheets are constructed by polynuclear helical-like chains. Compounds 3–5 are extremely similar in structure, in which Ln atoms are bridged into rod-shaped chains by carboxylate groups. For compounds 6–10, the coordination layers are built up from 1-D zig-zag chains. The 3-D supramolecular frameworks of 1–10 are finally formed through the alternate stack of Ln coordination layers and 4,4′-bipy layers based on hydrogen bonding interactions. Compound 7 displays luminescent property.
TL;DR: The first coordination compounds of 1,2,3,4-butanetetetracarboxylate anion (butca4-) were prepared and their X-ray crystal structures and magnetic properties investigated as discussed by the authors.
Abstract: The first coordination compounds of 1,2,3,4-butanetetracarboxylate anion (butca4-) of the formula [M2(butca)(H2O)5]n·2nH2O [M = Mn(II) (1), Co(II) (2), and Ni(II) (3)] were prepared and their X-ray crystal structures and magnetic properties investigated. The three complexes have a very similar two-dimensional structure which consists of (4,4) networks, 1 and 2 being isostructural. The tetracarboxylate ligand acts as a 4-fold connector leading to two-dimensional (4,4) networks of metal atoms, this topology being possible because of its planar conformation. The nodes of these networks are formed by dinuclear motifs which exhibit the unusual (μ-aqua)bis(μ-carboxylate) bridging unit which is analogous to that observed in some molecules of biological interest. The variable-temperature magnetic susceptibility measurements of 1−3 show that 1 and 2 are antiferromagnetically coupled systems whereas 3 exhibits a ferromagnetic behavior. The analysis of the magnetic data of 1−3 through a simple dinuclear model allowe...
TL;DR: A new soft chemical route to [Ta6O19]8- has been developed by the dissolution of [Ta(O2)4)4- in conditions alkaline enough to arrest formation of Ta2O5, followed by [VO4]3--catalyzed decomposition of the peroxide ligands and crystallization of the salt.
Abstract: A new soft chemical route to [Ta6O19]8− has been developed by the dissolution of [Ta(O2)4]3− in conditions alkaline enough to arrest formation of Ta2O5, followed by [VO4]3−-catalyzed decomposition of the peroxide ligands and crystallization of the salt. An average of bond lengths and angles from isostructural salts of [Ta6O19]8− and [Nb6O19]8− indicate there is an increase in terminal M(ηO) bond lengths and M-µ2-O–M angles and a decrease in bridging µ2-O–M bond lengths in [Ta6O19]8−, although the central µ6-O–M bond lengths are identical within experimental error. Two new structures of Na7[HNb6O19]·15H2O (1) and Na8[Ta6O19]·15H2O (2) are exemplary of the fact that protonated µ2-OH are observed exclusively in the niobates. In these structures, the metal-oxide framework, seven sodium atoms, and all fifteen water molecules are located in identical unit cell positions, but in 2 an eighth charge-balancing sodium is located in close proximity to the protonated µ2-OH in 1. Differences in the basicity of Nb(V)- and Ta(V)-bound oxygen atoms are also manifested at the surfaces of 17O-enriched powders of Nb2O5 and Ta2O5. Oxygen exchange at the surface of these materials readily takes place at both terminal and bridging sites in Nb2O5 but only at terminal sites in Ta2O5.
TL;DR: Analysis of the crystal and electronic structure indicate that the polyanionic subnetwork requires 19 additional electrons, whereas only 18 electrons are provided by the cations, so apparent "electron deficiency" necessitates the presence of an interstitial atom.
Abstract: Seven cadmium- and zinc-containing Zintl phases, A9Zn(4+x)Pn9 and A9Cd(4+x)Pn9 (0 < or = x < or = 0.5), A = Ca, Sr, Yb, Eu; Pn = Sb, Bi, have been synthesized, and their structures have been determined by single-crystal X-ray diffraction. All compounds are isostructural and crystallize in the centrosymmetric orthorhombic space group Pbam (no. 55, Z = 2), and their structures feature tetrahedra of the pnicogens, centered by the transition metal. The tetrahedra are not isolated but are connected through corner sharing to form ribbons, which are separated by the divalent cations. The occurrence of a small phase width and its variation across this family of compounds has been systematically studied by variable temperature crystallography, resistivity, and magnetic susceptibility measurements, and these results have been reconciled with electronic structure calculations performed using the tight-binding linear muffin-tin orbital (TB-LMTO-ASA) method. These analyses of the crystal and electronic structure indicate that the polyanionic subnetwork requires 19 additional electrons, whereas only 18 electrons are provided by the cations. Such apparent "electron deficiency" necessitates the presence of an interstitial atom in order for an optimal bonding to be achieved; however, an interplay between the sizes of the cations and anions and the total valence electron concentration (governed by the stoichiometry breadth) is suggested as a possible mechanism for achieving structure stability. The structural relationship between these and some known structures with two-dimensional layers are discussed as well.
TL;DR: Based on an unsymmetrical 2-pyridylphosphonate ligand, two types of Ln(III)-Cu(II) compounds with three-dimensional structures were obtained under hydrothermal conditions, which showed that both the lanthanide contraction and the electron configuration of Cu( II) play important roles.
Abstract: Based on an unsymmetrical 2-pyridylphosphonate ligand, two types of Ln(III)-Cu-II compounds with three-dimensional structures were obtained under hydrothermal conditions, namely, Ln(2)Cu(3)(C5H4NPO3)(6)center dot 4H(2)O (1 center dot Ln: Ln = La, Ce, Pr, Nd) and Ln(2)Cu(3)(C5H4NPO3)(6) (2-Ln; Ln = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho). Compounds 1.Ln are isostructural and crystallize in chiral cubic space group I2(1)3. In these structures, each Ln ion is nine-coordinate and has a tricapped triprismatic geometry, while each Cu center is six-coordinate with an octahedral environment. The {LnO(9)} polyhedra and {CuN2O4} octahedra are connected by edge sharing to form an inorganic open framework structure with a 3-connected 10-gon (10,3) topology in which the Ln and Cu atoms are alternately linked by the phosphonate oxygen atoms. Compounds 2-Ln are isostructural and crystallize in trigonal space group R(3) over bar. In these structures, the {LnO(6)} octahedra are triply bridged by the {CPO3} tetrahedra by corner sharing to form an infinite chain along the c axis. Each chain is connected to its six equivalents through corner sharing of {CPO3} tetrahedra and {CuN2O2} planes to form a three-dimensional framework structure in which the Ln and Cu atoms are linked purely by O-P-O units. The formation of these two types of structures is rationalized by quantum chemical calculations, which showed that both the lanthanide contraction and the electron configuration of Cu-II play important roles. When Cu-II was replaced by Zn-II, only the first type of compounds resulted. The magnetic properties of complexes 1.Ln and 2.Ln were investigated. The nature of Ln(III)-Cu-II (Ln = Ce, Pr, Nd) interactions is illustrated by comparison with their Ln(III)-Zn-II analogues.
TL;DR: In order to shed light on the proton distributions and order/disorder in high-pressure delta-Al(OH)3 and delta-alOOH phases, two-dimensional, high-resolution 1H CRAMPS (FSLG)-MAS NMR and 27Al 3QMAS NMRI spectra have been obtained as mentioned in this paper.
Abstract: In order to shed light on the proton distributions and order/disorder in high-pressure delta-Al(OH)3 and delta-AlOOH phases, two-dimensional, high-resolution 1H CRAMPS (FSLG)-MAS NMR and 27Al 3QMAS NMR spectra have been obtained. For delta-Al(OH)3, the 1H CRAMPS-MAS NMR revealed two peaks with an intensity ratio close to 2:1. The 27Al MAS and 3QMAS NMR suggest a single Al site with a well-defined local structure. For delta-AlOOH, the 1H and 27Al NMR indicate the presence of a single H and Al site each. These results are consistent with crystal structures refined from X-ray diffraction. For comparison, 1H MAS and CRAMPS-MAS NMR spectra were also obtained for several other hydroxides/oxyhydroxides, including In(OH)3 and InOOH that have similar structures to delta-Al(OH)3 and delta-AlOOH, respectively. These data not only provide additional insights into the proton distributions in these important crystal structure classes but also together provide a better defined quantitative correlation between 1H chemical shift and hydrogen-bonding O...O distance.
TL;DR: In this article, the self-assembly of isonicotinic acid with metal salts under hydrothermal conditions gave two isostructural 3D 4d-4f coordination polymers, Ln2Ag4(OX)(IN)6(H2O)1.5
TL;DR: In this paper, three novel isostructural complexes were synthesized at room temperature and structurally characterized by elemental analysis, IR and single crystal X-ray diffraction, which exhibit a similar mononuclear structure, in which the metal ion is coordinated by two gatifloxacin and two aqua ligands to furnish a distorted octahedral geometry.
Abstract: Three novel isostructural complexes M(gatx)2(H2O)2·4H2O [gatx=gatifloxacin, M=Zn (1), Ni (2) and Co (3)] were synthesized at room temperature and structurally characterized by elemental analysis, IR and single crystal X-ray diffraction, which exhibit a similar mononuclear structure, in which the metal ion is coordinated by two gatifloxacin and two aqua ligands to furnish a distorted octahedral geometry, and show different activities against staphylococcus due to the different metal ions in the structures.
TL;DR: In this article, the pressure-driven tetragonal-to-monoclinic phase transition in CaWO4 and related scheelite-structured orthotungstates is analyzed in terms of spontaneous strains.
Abstract: The pressure-driven tetragonal-to-monoclinic phase transition in CaWO4 and related scheelite-structured orthotungstates is analysed in terms of spontaneous strains. Based upon our previous high-pressure X-ray diffraction results and the Landau theory, it is suggested that the scheelite-to-fergusonite transition is of second order in nature.