Synthesis, structure of [H3dien]·(MF6)·H2O (M=Cr, Fe) and Fe Mössbauer study of [H3dien]·(FeF6)·H2O

Single crystals of [H₃dien]·(FeF₆)·H₂O (I) and [H₃dien]·(CrF₆)·H₂O (II) are obtained by solvothermal synthesis under microwave heating. I is orthorhombic (Pna2₁) with a=11.530(2) Å, b=6.6446(8) Å, c=13.787(3) Å, V=1056.3(2) Å³ and Z=4. II is monoclinic (P2₁/c) with a=13.706(1) Å, b=6.7606(6) Å, c=11.3181(9) Å, β=99.38(1)°, V=1034.7(1) Å³ and Z=4. The structure determinations, performed from single crystal X-ray diffraction data, lead to the R₁/wR₂ reliability factors 0.028/0.066 for I and 0.035/0.102 for II. The structures of I and II are built up from isolated FeF₆ or CrF₆ octahedra, water molecules and triprotonated amines. In both structures, each octahedron is connected by hydrogen bonds to six organic cations and two water molecules. The iron-based compound is also characterized by ⁵⁷Fe Mössbauer spectrometry: the hyperfine structure confirms the presence of Fe³⁺ in octahedral coordination and reveals the existence of paramagnetic spin fluctuations.     

Hydrothermal syntheses and structures of the uranyl tellurates AgUO2(HTeO5) and Pb2UO2(TeO6)

Two uranyl tellurates, AgUO₂(HTeO₅) (1) and Pb₂UO₂(TeO₆) (2), were synthesized under hydrothermal conditions and were structurally, chemically, and spectroscopically characterized. 1 crystallizes in space group Pbca, a=7.085(2) Å, b=11.986(3) Å, c=13.913(4) Å, V=1181.5(5) Å³, Z=8; 2 is in P2(1)/c, a=5.742(1) Å, b=7.789(2) Å, c=7.928(2) Å, V=90.703(2) Å³, and Z=2. These are the first structures reported for uranyl compounds containing tellurate. The U⁶⁺ cations are present as (UO₂)²⁺ uranyl ions that are coordinated by O atoms to give pentagonal and square bipyramids in compounds 1 and 2, respectively. The structural unit in 1 is a sheet consisting of chains of edge-sharing uranyl pentagonal bipyramids that are one bipyramid wide, linked through the dimers of TeO₆ octahedra. In 2, uranyl square bipyramids share each of their equatorial vertices with different TeO₆ octahedra, giving a sheet with the autunite-type topology. Sheets in 1 and 2 are connected through the low-valence cations that are located in the interlayer region. The structures of 1 and 2 are compared to those of uranyl compounds containing octahedrally coordinated cations.     

Synthesis and structure of [C6N4H20]0.5[B5O6(OH)4]: A new organically templated pentaborate with white-light-emission

A new organically templated pentaborate [C₆N₄H₂₀]_0.5[B₅O₆(OH)₄] (1a) was prepared by reactions of triethylenetetramine (TETA) with excess boric acid in aqueous solution and characterized by elemental analysis, FTIR, TG-DTA, powder X-ray diffraction and photoluminescence spectroscopy. The structure of 1a was determined by a single-crystal X-ray diffraction. It crystallizes in the monoclinic system with space group P2(1)/c, a=9200(3) Å, b=14.121(5) Å, c=10.330(4) Å, β=91.512(4)°, V=1341.4(9) Å³, and Z=4. The luminescent properties of the compound were studied, and a green-blue luminescence occurs with an emission maximum at 507 nm upon excitation at 430 nm. The photoluminescence of 1a can be modified from green-blue to white by means of a simple heat-treatment process. The white-light-emission of sample 1c makes the pentaborate a good candidate for display and lighting applications in the white LED.     

Synthesis and properties of pyrazine-pillared Ag3Mo2O4F7 and AgReO4 layered phases

The new pyrazine-pillared solids, AgReO₄(C₄H₄N₂) (I) and Ag₃Mo₂O₄F₇(C₄H₄N₂)₃ (C₄H₄N₂=pyrazine, pyz) (II), were synthesized by hydrothermal methods at 150 °C and characterized using single crystal X-ray diffraction (I—P2₁/c, No. 14, Z=4, a=7.2238(6) Å, b=7.4940(7) Å, c=15.451(1) Å, β=92.296(4)°; II—P2/n, No. 13, Z=2, a=7.6465(9) Å, b=7.1888(5) Å, c=19.142(2) Å, β=100.284(8)°), thermogravimetric analysis, UV-Vis diffuse reflectance, and photoluminescence measurements. Individual Ag(pyz) chains in I are bonded to three perrhenate ReO₄^- tetrahedra per layer, while each layer in II contains sets of three edge-shared Ag(pyz) chains (π-π stacked) that are edge-shared to four Mo₂O₄F₇^3- dimers. A relatively small interlayer spacing results from the short length of the pyrazine pillars, and which can be removed at just slightly above their preparation temperature, at >150-175 °C, to produce crystalline AgReO₄ for I, and Ag₂MoO₄ and an unidentified product for II. Both pillared solids exhibit strong orange-yellow photoemission, at 575 nm for I and 560 nm for II, arising from electronic excitations across (charge transfer) band gaps of 2.91 and 2.76 eV in each, respectively. Their structures and properties are analyzed with respect to parent ‘organic free’ silver perrhenate and molybdate solids which manifest similar photoemissions, as well as to the calculated electronic band structures.     

Synthesis and crystal structure of new uranyl tungstates M2(UO2)(W2O8) (M=Na, K), M2(UO2)2(WO5)O (M=K, Rb), and Na10(UO2)8(W5O20)O8

The solid-state reactions of UO₃ and WO₃ with M₂CO₃ (M=Na, K, Rb) at 650°C for 5 days result, accordingly the starting stoichiometry, in the formation of M₂(UO₂)(W₂O₈) (M=Na (1), K (2)), M₂(UO₂)₂(WO₅)O (M=K (3), Rb (4)), and Na₁₀(UO₂)₈(W₅O₂₀)O₈ (5). The crystal structures of compounds 2, 3, 4, and 5 have been determined by single-crystal X-ray diffraction using Mo(Kα) radiation and a charge-coupled device detector. The crystal structures were solved by direct methods and Fourier difference techniques, and refined by a least-squares method on the basis of F² for all unique reflections. For (1), unit-cell parameters were determined from powder X-ray diffraction data. Crystallographic data: 1, monoclinic, a=12.736(4) Å, b=7.531(3) Å, c=8.493(3) Å, β=93.96(2)°, ρ_cal=6.62(2) g/cm³, ρ_mes=6.64(1) g/cm³, Z=4; 2, orthorhombic, space group Pmcn, a=7.5884(16) Å, b=8.6157(18) Å, c=13.946(3) Å, ρ_cal=6.15(2) g/cm³, ρ_mes=6.22(1) g/cm³, Z=8, R1=0.029 for 80 parameters with 1069 independent reflections; 3, monoclinic, space group P2₁/n, a=8.083(4) Å, b=28.724(5) Å, c=9.012(4) Å, β=102.14(1)°, ρ_cal=5.83(2) g/cm³, ρ_mes=5.90(2) g/cm³, Z=8, R1=0.037 for 171 parameters with 1471 reflections; 4, monoclinic, space group P2₁/n, a=8.234(1) Å, b=28.740(3) Å, c=9.378(1) Å, β=104.59(1)°, ρ_cal=6.13(2) g/cm³,  g/cm³, Z=8, R1=0.037 for 171 parameters with 1452 reflections; 5, monoclinic, space group C2/c, a=24.359(5) Å, b=23.506(5) Å, c=6.8068(14) Å, β=94.85(3)°, ρ_cal=6.42(2) g/cm³,  g/cm³, Z=8, R1=0.036 for 306 parameters with 5190 independent reflections. The crystal structure of 2 contains linear one-dimensional chains formed from edge-sharing UO₇ pentagonal bipyramids connected by two octahedra wide (W₂O₈) ribbons formed from two edge-sharing WO₆ octahedra connected together by corners. This arrangement leads to [UW₂O₁₀]²⁻ corrugated layers parallel to (001). Owing to the unit-cell parameters, compound 1 probably contains similar sheets parallel to (100). Compounds 3 and 4 are isostructural and the structure consists of bi-dimensional networks built from the edge- and corner-sharing UO₇ pentagonal bipyramids. This arrangement creates square sites occupied by W atoms, a fifth oxygen atom completes the coordination of W atoms to form WO₅ distorted square pyramids. The interspaces between the resulting [U₂WO₁₀]²⁻ layers parallel to plane are occupied by K or Rb atoms. The crystal structure of compound 5 is particularly original. It is based upon layers formed from UO₇ pentagonal bipyramids and two edge-shared octahedra units, W₂O₁₀, by the sharing of edges and corners. Two successive layers stacked along the [100] direction are pillared by WO₄ tetrahedra resulting in sheets of double layers. The sheets are separated by Na⁺ ions. The other Na⁺ ions occupy the rectangular tunnels created within the sheets. In fact complex anions W₅O₂₀¹⁰⁻ are built by the sharing of the four corners of a WO₄ tetrahedron with two W₂O₁₀ dimmers, so, the formula of compound 5 can be written Na₁₀(UO₂)₈(W₅O₂₀)O₈.     

Syntheses, structure and magnetic properties of pillared layered diphosphonates: M2(O3PC6H4PO3)(H2O)2 (M=Co, Ni)

This paper describes the hydrothermal syntheses of two isostructural metal bisphosphonates: M₂(O₃PC₆H₄PO₃)(H₂O)₂ [M=Co^II (1), Ni^II (2)]. Single-crystal structure determination of compound 1 revealed a pillared layered structure in which the phenyl groups connect the inorganic layers of cobalt phosphonate. Crystal data for 1: orthorhombic, space group Pnnm, a=19.306(5), b=4.8293(12), c=5.6390(14) Å, V=525.7(2) Å³, Z=2. Magnetic susceptibility data indicate that antiferromagnetic interactions are mediated in both cases.     

Syntheses, crystal structures and spectroscopic properties of Ag2Nb[P2S6][S2] and KAg2[PS4]

Ag₂Nb[P₂S₆][S₂] (1) was obtained from the direct solid state reaction of Ag, Nb, P₂S₅ and S at 500 °C. KAg₂[PS₄] (2) was prepared from the reaction of K₂S₃, Ag, Nd, P₂S₅ and extra S powder at 700 °C. Compound 1 crystallizes in the orthorhombic space group Pnma with a=12.2188(11), b=26.3725(16), c=6.7517(4) Å, V=2175.7(3) Å³, Z=8. Compound 2 crystallizes in the non-centrosymmetric tetragonal space group with lattice parameters a=6.6471(7), c=8.1693(11) Å, V=360.95(7) Å³, Z=2. The structure of Ag₂Nb[P₂S₆][S₂] (1) consists of [Nb₂S₁₂], [P₂S₆] and new found puckered [Ag₂S₄] chains which are along [001] direction. The Nb atoms are located at the center of distorted bicapped trigonal prisms. Two prisms share square face of two [S₂²⁻] to form one [Nb₂S₁₂] unit, in which Nb-Nb bond is formed. The [Nb₂S₁₂] units share all S²⁻ corners with ethane-like [P₂S₆] units to form 14-membered rings. The novel puckered [Ag₂S₄] chains are composed of distorted [AgS₄] tetrahedra and [AgS₃] triangles that share corners with each other. These chains are connected with [P₂S₆] units and [Nb₂S₁₂] units to form three-dimensional frame work. The structural skeleton of 2 is built up from [AgS₄] and [PS₄] tetrahedra linked by corner-sharing. The three-dimensional anionic framework contains orthogonal, intersecting tunnels directed along [100] and [010]. This compound possesses a compressed chalcopyrite-like structure. The structure is compressed along [001] and results from eight coordination sphere for K⁺. Both compounds are characterized with UV/vis diffuse reflectance spectroscopy and compound 1 with IR and Raman spectra.     

Two metal chalcogenides, Hg2Te2X2 (XBr, I): 3-D framework constructed from novel left-handed helices

Two isostructural metal chalcogenides, Hg₂Te₂Br₂ (1) and Hg₂Te₂I₂ (2), were obtained by solid-state reactions and structurally characterized. Compounds 1 and 2 crystallize in the acentric space group P4₃2₁2 of the tetragonal system with eight formula units in a cell: a=10.2388(9), c=14.480(2) Å, V=1518.0(3) Å³, R₁/wR₂=0.0670/0.1328 for 1 and a=10.711(3), c=15.025(8) Å, V=1724(1) Å³, R₁/wR₂=0.0637/0.1233 for 2. Both compounds are characterized by a three-dimensional (3-D) framework structure, which is composed by interconnected left-handed helices formed by both tetrahedral and trigonal Hg atoms. Optical absorption spectra of 1 and 2 reveal the presence of sharp optical gaps of 2.06 and 1.85 eV, respectively, suggesting that both materials are semiconductors. TG-DTA measurements show that both compounds are thermally stable up to 200 °C. The composition of both compounds is well confirmed by the semiquantitative microscope analyses.     

Structure and microstructure of the high pressure synthesised misfit layer compound [Sr2O2][CrO2]1.85

The strontium chromium oxide [Sr₂O₂][CrO₂]_1.85 misfit layer compound has been synthesised at high-pressure and high-temperature conditions. Electron diffraction patterns and high-resolution transmission electron microscopy images along [001] show the misfit character of the different layers composing the structure with a supercell along the incommensurate parameter b≈7b₁≈13b₂. The modulated crystal structure has been refined within the superspace formalism against single-crystal X-ray diffraction data, employing the (3+1)-dimensional superspace group C′nmb(0σ₂0)0 0 s. The compound has a composite structure with lattice parameters a₁=5.182(1) Å, b₁=5.411(1) Å, c₁=18.194(3) Å for the first, SrO, subsystem and the same a and c, but with b₂=2.925(1) Å for the second, CrO₂, subsystem. The layer stacking is similar to that of orthorhombic PbS(TiS₂)_1.18, but with a much stronger intersubsytem bonding in the case of the oxide. The intersubsystem lattice mismatch is mainly handled by displacement modulations of the Sr atoms, correlated with modulations of the valence, the coordination and the anisotropic displacement parameters.     

Synthesis, crystal structure and NLO property of a nonmetal pentaborate [C6H13N2][B5O6(OH)4]

A nonmetal pentaborate [C₆H₁₃N₂][B₅O₆(OH)₄] (1) has been synthesized by 1,4-diazabicyclo[2.2.2] octane (DABCO) and boric acid, and characterized by single-crystal X-ray diffraction, FTIR, elemental analysis, and thermogravimetric analysis. Compound 1 crystallizes in the monoclinic system with space group Cc (no. 9), a=10.205(2) Å, b=14.143(3) Å, c=11.003(2) Å, β=113.97(3)°, V=1451.1(5) Å³, Z=4. The anionic units, [B₅O₆(OH)₄]⁻, are interlinked via hydrogen bonding to form a three-dimensional (3D) supramolecular network containing large channels, in which the protonated [C₆H₁₃N₂]⁺ cations are located. Second-harmonic generation (SHG) measurements on the powder samples reveal that 1 exhibits SHG efficiency approximately 0.9 times that of potassium dihydrogen phosphate (KDP).     

An unprecedented extended architecture constructed from a 2-D interpenetrating cationic coordination framework templated by SiW12O40 anion

A novel inorganic-organic hybrid compound based on polyoxometalates (POMs) and organic ligand formulated as [Cu₂(bpp)₄(H₂O)₂](SiW₁₂O₄₀)∼6H₂O (1) [bpp=1,3-bis(4-pyridyl)propane], was hydrothermally synthesized and structurally characterized by elemental analysis, single-crystal X-ray diffraction analysis, IR, TG, and cyclic voltammetry. Crystal data for 1: Orthorhombic, Pbcn, a=23.0085(19) Å, b=14.6379(12) Å, c=23.6226(19) Å, V=7956.0(11) Å³, Z=4, Dc=3.315 g cm^-3, and R(final)=0.0826. X-ray diffraction study reveals that compound 1 was the first interpenetrating network of 2-D metal-organic cationic coordination framework [Cu₂(bpp)₄(H₂O)₂]_n⁴ⁿ⁺, in which Keggin-type anions SiW₁₂O₄₀^4- has been used as a non-coordinating anionic template. The electrochemical property of 1-bulk modified carbon paste electrode (1-CPE) has been studied, and the results indicate that 1-CPE has good electrocatalytic activities toward the reduction of nitrite in 1 M H₂SO₄ aqueous solution.     

Synthesis, crystal structure, infrared and Raman spectra of Sr4Cu3(AsO4)2(AsO3OH)4·3H2O and Ba2Cu4(AsO4)2(AsO3OH)3

The two new compounds, Sr₄Cu₃(AsO₄)₂(AsO₃OH)₄·3H₂O (1) and Ba₂Cu₄(AsO₄)₂(AsO₃OH)₃(2), were synthesized under hydrothermal conditions. They represent previously unknown structure types and are the first compounds synthesized in the systems SrO/BaO-CuO-As₂O₅-H₂O. Their crystal structures were determined by single-crystal X-ray diffraction [space group C2/c, a=18.536(4) Å, b=5.179(1) Å, c=24.898(5) Å, β=93.67(3)°, V=2344.0(8) Å³, Z=4 for 1; space group P4₂/n, a=7.775(1) Å, c=13.698(3) Å, V=828.1(2) Å³, Z=2 for 2]. The crystal structure of 1 is related to a group of compounds formed by Cu²⁺-(XO₄)³⁻ layers (X=P⁵⁺, As⁵⁺) linked by M cations (M=alkali, alkaline earth, Pb²⁺, or Ag⁺) and partly by hydrogen bonds. In 1, worth mentioning is the very short hydrogen bond length, D···A=2.477(3) Å. It is one of the examples of extremely short hydrogen bonds, where the donor and acceptor are crystallographically different. Compound 2 represents a layered structure consisting of Cu₂O₈ centrosymmetric dimers crosslinked by As1φ₄ tetrahedra, where φ is O or OH, which are interconnected by Ba, As2 and hydrogen bonds to form a three-dimensional network. The layers are formed by Cu₂O₈ centrosymmetric dimers of CuO₅ edge-sharing polyhedra, crosslinked by As1O₄ tetrahedra. Vibrational spectra (FTIR and Raman) of both compounds are described. The spectroscopic manifestation of the very short hydrogen bond in 1, and ABC-like spectra in 2 were discussed.     

New open-framework in the uranyl vanadates A3(UO2)7(VO4)5O (A=Li, Ag) with intergrowth structure between A(UO2)4(VO4)3 and A2(UO2)3(VO4)2O

New uranyl vanadates A₃(UO₂)₇(VO₄)₅O (M=Li (1), Na (2), Ag (3)) have been synthesized by solid-state reaction and their structures determined from single-crystal X-ray diffraction data for 1 and 3. The tetragonal structure results of an alternation of two types of sheets denoted S for _∞²[UO₂(VO₄)₂]⁴⁻ and D for _∞²[(UO₂)₂(VO₄)₃]⁵⁻ built from UO₆ square bipyramids and connected through VO₄ tetrahedra to _∞¹[U(3)O₅-U(4)O₅]⁸⁻ infinite chains of edge-shared U(3)O₇ and U(4)O₇ pentagonal bipyramids alternatively parallel to a- and b-axis to construct a three-dimensional uranyl vanadate arrangement. It is noticeable that similar _∞[UO₅]⁴⁻ chains are connected only by S-type sheets in A₂(UO₂)₃(VO₄)₂O and by D-type sheets in A(UO₂)₄(VO₄)₃, thus A₃(UO₂)₇(VO₄)₅O appears as an intergrowth structure between the two previously reported series. The mobility of the monovalent ion in the mutually perpendicular channels created in the three-dimensional arrangement is correlated to the occupation rate of the sites and by the geometry of the different sites occupied by either Na, Ag or Li. Crystallographic data: 293 K, Bruker X8-APEX2 X-ray diffractometer equipped with a 4 K CCD detector, MoKα, λ=0.71073 Å, tetragonal symmetry, space group P4¯m2, Z=1, full-matrix least-squares refinement on the basis of F²; 1,a=7.2794(9) Å, c=14.514(4) Å, R1=0.021 and wR2=0.048 for 62 parameters with 782 independent reflections with I?2σ(I); 3, a=7.2373(3) Å, c=14.7973(15) Å, R1=0.041 and wR2=0.085 for 60 parameters with 1066 independent reflections with I?2σ(I).     

Synthesis, characterization and crystal structure of a novel Os(II)-supported tungstoarsenate [HAsW7O28Os(dmso)3]

Reaction of tri-lacunary Keggin tungstoarsenate with osmium complex Os(dmso)₄Cl₂ under mild condition led to the formation of a novel Os (II)-supported tungstoarsenate Na₅(NH₄)[HAsW₇O₂₈Os(dmso)₃]·15H₂O (1a). Single-crystal X-ray diffraction analysis shows that compound 1a crystallizes in the monoclinic space group P2₁/c (no. 14) with a=14.9166(12) Å, b=23.6935(19) Å, c=16.5349(14) Å, β=92.7950(10)°, V=5836.9(8) Å³, Z=4 with R₁=0.0453. The crystal structure reveals two features: (1) the polyanion [HAsW₇O₂₈Os(dmso)₃]⁶⁻ (1) consists of a Os(dmso)₃ unit linked to a tungstoarsenate fragment {HAsW₇O₂₈} via two Os-O-W bonds and one Os-O-As bond resulting in an assembly with C_s symmetry, which represents a novel mode of Os-coordination to a polyoxoanion framework; (2) 3D architecture assembled by the polyanion 1 and sodium linkers. In addition, the compound 1a was well characterized by the multinuclear NMR (¹³C, ¹H), IR spectroscopy, UV-vis spectroscopy, elemental analysis, and cyclic voltammetry (CV).     

Building three-dimensional metal phosphites from the corner-shared four-membered rings chain

Three new compounds, a one-dimensional (1D) zinc phosphite, (C₄H₈N₂H₄)[Zn(HPO₃)₂] (I), two three-dimensional (3D) metal phosphites (C₄H₈N₂H₄)[Zn₃(HPO₃)₄] (II) and (C₄H₈N₂H₄)[Zn_(3−x)Co_x(HPO₃)₄(H₂O)₂] (x≈0.83) (III) have been synthesized under hydrothermal conditions templated by piperazine and characterized by single-crystal X-ray diffraction, XRD, IR, UV-vis spectra and SQUID magnetometer. Compound I displays 1D chain-like structure, containing corner-shared (cs) four-membered rings. Interestingly, the structures of II and III show 1D chains similar to those observed in I. It is noteworthy that III represents the first cobalt-substituted zinc-phosphite. Crystal data: I, monoclinic, C2/c, a=17.748(2) Å, b=7.428(9) Å, c=8.8071(11) Å, β=105.345(3)°, V=1091.9 Å³, Z=4. II, Monoclinic P2₁/c, a=9.9435(4) Å, b=10.1438(3) Å, c=17.8164(5) Å, β=95.665(2)°, V=1788.27 Å³, Z=4, and III, Monoclinic P2₁/c, a=7.2338(2) Å, b=15.0238(5) Å, c=9.2153(3) Å, β=107.741(2)°, V=953.88(5) Å³, Z=2.     

Hydrothermal synthesis, crystal structure, thermal behavior and spectroscopic and magnetic properties of two new organically templated fluoro-vanadyl-hydrogenarsenates: (R)0.5[(VO)(HAsO4)F] (R: Ethylenediammonium and piperazinium)

Two new fluoro-vanadyl-hydrogenarsenate compounds templated by ethylenediamine and piperazine with formula, (C₂N₂H₁₀)_0.5[(VO)(HAsO₄)F] (1) and (C₄N₂H₁₂)_0.5[(VO)(HAsO₄)F] (2), respectively, have been synthesized by using mild hydrothermal conditions under autogenous pressure. The crystal structures have been solved from single-crystal X-ray diffraction data. The phases crystallize in the P2₁/c monoclinic space group with the unit-cell parameters a=7.8634(4) Å, b=7.7658(4) Å, c=10.4195(6) Å, β=101.524(5)° for compound (1) and a=6.301(1) Å, b=10.244(1) Å, c=10.248(1) Å and β=95.225(1)° for compound (2). These phases exhibit a layered inorganic framework. In both cases, the structure is built from secondary building units (SBU) which are formed by [V₂O₈F₂] edge-shared dimeric vanadyl octahedra, connected by the vertices to two hydrogenarsenate tetrahedra. The repetition of this SBU unit originates sheets along the [1 0 0] direction. The ethylenediammonium and piperazinium cations are located inside the interlayer space. The limit of thermal stability for compounds (1) and (2) is, approximately, 250 and 230 °C, respectively. Near this temperature, both phases loose their organic cations and the fluoride anions. The diffuse reflectance spectra confirm the presence of vanadyl ions, in which the vanadium(IV) cations have a d¹ electronic configuration in a slightly distorted octahedral environment. ESR spectra of both phases are isotropic with mean g-values of 1.93 and 1.96 for ethylendiamine and piperazine phases, respectively. Magnetic measurements for (1) and (2) indicate the existence of antiferromagnetic exchange couplings.     

A layered vanadium arsenate network decorated with the directly coordinated organonitrogen ligands: [V4O7(HAsO4)2(o-phen)2] (o-phen=o-phenanthroline)

A novel layered vanadium arsenate [V₄O₇(HAsO₄)₂(o-phen)₂] 1 (o-phen=o-phenanthroline) was synthesized by the hydrothermal reaction of V₂O₅, ZnCl₂, Na₂HAsO₄·7H₂O, o-phenanthroline (o-phen) and water. Its structure was determined by elemental analyses, ESR spectrum, XPS spectrum, TG analysis, IR spectrum and the single-crystal X-ray diffraction. Compound 1 crystallizes in monoclinic system, space group P2/c, a=10.122(2) Å, b=9.867(2) Å, c=15.367(3) Å, β=102.83(3)°, V=1496.4(5) Å³, Z=1, λ(MoKα)=0.71073 Å, (R(F)=0.0397 for 3422 reflections). Data were collected on a Rigaku R-AXIS RAPID IP diffractometer at 293 K in the range of 2.06°<θ<27.48°. The title compound contains an unusual two-dimensional (2D) As-V-O layer with four-, six- and eight-membered rings. The chelating o-phen ligands project perpendicularly above and below the undulating layer. 1 represents the first example of 2D inorganic vanadium arsenate backbone grafted with the directly coordinated organic ligands. Furthermore, the 3D supermolecular architecture is formed by π-π stacking interactions of the o-phen groups between adjacent layers.     

Redistribution reactions of heteroleptic barium iodide derivatives: Synthesis and structures of trans-BaI2(DME)(triglyme), cis-BaI2(DME)(tetraglyme) and [Ba(tetraglyme)2]I2 · C7H8

The reaction between BaI₂ · 2H₂O and NaHFIP [HFIP = OCH(CF₃)₂] in a 1:1 stoichiometry gave the heterometallic compound NaBaI₂(HFIP)(H₂O)(THF)_0.5 (1). Attempts to recrystallize 1 in the presence of N- or O-donor ligands lead to redistribution reactions. Barium iodide adducts such as BaI₂(DME)₃ (2), trans-BaI₂(DME)(triglyme) (3) and cis-BaI₂(DME)(tetraglyme) (4) were isolated with DME as solvent. A similar behavior was observed for the reaction between BaI₂ · 2H₂O and NaTFA (TFA = O₂CCF₃) in a 1:1 stoichiometry in THF, and [Ba(tetraglyme)₂]I₂ · C₇H₈ (6) was isolated in the presence of excess tetraglyme. All compounds have been characterized by elemental analysis, IR and ¹H NMR as well as single crystal X-ray studies for 3, 4 and 6. Compounds 3 and 4 are covalent adducts with eight- and nine-coordinate barium, respectively. Compound 6 is an ionic compound where two tetraglyme ligands wrap the 10-coordinate barium cation in a helical fashion. The presence of DME actually allows the coordination number of barium in the mixed-ligand adducts 3 and 4 to be tuned. The average Ba–O bond lengths (2.80 for 3 to 2.87 Å for 6) reflect the coordination number of the metal. The same observation is valid for the average Ba–I bond distance, 3.442 for 3 vs. 3.536 Å for 4.     

Two isotypic diphosphates LiM2H3(P2O7)2 (M=Ni, Co) containing ferromagnetic zigzag MO6 chains

Two new isotypic phosphates LiNi₂H₃(P₂O₇)₂ (1) and LiCo₂H₃(P₂O₇)₂ (2) have been hydrothermally synthesized and structurally characterized by the single-crystal X-ray diffraction technique. They crystallize in the monoclinic space group C2/c with the lattice: a=10.925(2) Å, b=12.774(3) Å, c=8.8833(18) Å, β=123.20(3)° for 1 and a=10.999(2) Å, b=12.863(3) Å, c=8.9419(18) Å, β=123.00(3)° for 2. The transition metal atoms are octahedrally coordinated, whereas the lithium and phosphorus atoms are all tetrahedrally coordinated. As the lithium-induced derivatives of MH₂P₂O₇ (M=Ni, Co), 1 and 2 possess the same structure with MH₂P₂O₇ in terms of topology, comprising the MO₆ zigzag chains and P₂O₇ as the interchain groups. The magnetisms of 1 and 2 could be interpreted by adopting a quasi-one-dimensional (1D) zigzag chain model as that in their parent compounds: both 1 and 2 have ferromagnetic (FM) NiO₆/CoO₆ chains; 1 shows a FM cluster glass behavior at low temperatures, which is originated from the possible antiferromagnetic (AFM) next-nearest-neighbour intrachain interactions; 2 shows a AFM ordering at T_N=2.6 K and a metamagnetic transition at H_C=4.2 kOe at 1.8 K.     

Hydrothermal synthesis, crystal structures and fluorescence properties of three novel frameworks constructed with mixed ligands of isophthalic acid (1,3-BDC) and 2,3-di-2-pyridylquinoxaline (Dpdq): [M(1,3-BDC)(Dpdq)(H2O)m] · nH2O (M = Co, Cd or Zn)

Three novel metal-organic frameworks [M(1,3-BDC)(Dpdq)(H₂O)_m] · nH₂O, (M = Co^II (1), Cd^II (2) or Zn^II (3); m = 0, 1; n = 0, 1, 2, respectively) have been obtained from hydrothermal reactions of three different metal(II) nitrates with the same mixed ligands [isophthalic acid (1,3-BDC) and 2,3-di-2-pyridylquinoxaline (Dpdq)], and structurally characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction analyses. Single-crystal X-ray analyses show that each pair of metal ions are bridged by various coordination modes of 1,3-BDC ligands to form left- and right-handed helical chains in 1, linear chains in 2, and double chains in 3, respectively. N-containing flexible ligand Dpdq takes a chelating coordination mode acting as terminal ligand. In the compound 1, adjacent left- and right-handed helical chains are packed through hydrogen bonds to form a two-dimensional (2-D) structure. In the compounds 2 and 3, adjacent chains are further linked by hydrogen bonds and/or π-π stacking interactions to form a three-dimensional (3-D) distorted hexagon meshes supramolecular framework for 2 and a ZnS-related three-dimensional (3-D) topology for 3, respectively. The different structures of compounds 1-3 illustrate that the influence of the metal ions in the self-assembly of polymeric coordination architectures. In addition, compounds 2 and 3 exhibit blue emission in the solid state at room temperature.