Crystal chemistry of three new monodimensional fluorometalates templated with ethylenediamine

Three new monodimensional hybrid metal (Ti, In, Al) fluorides are synthesized with ethylenediamine (en) as a templating agent in solvothermal conditions assisted by microwave heating. All structures involve inorganic chains built up from TiO₂F₄ octahedra connected by two opposite O²⁻ vertices in [H₂en]·(TiOF₄) (I), from InF₆(H₂O) pentagonal bipyramids linked by F–F edges in [H₂en]·(InF₄(H₂O))₂·H₂O (II) and from (Al₇F₃₀)⁹⁻ polyanions sharing two opposite AlF₆ octahedra in [H₂en]₃·(Al₆F₂₄) (III). I is tetragonal, P4/ncc, a = 12.761(3) Å, c = 8.041(3) Å; II is orthorhombic, F2dd, a = 6.904(5) Å, b = 16.559(5) Å, c = 19.777(4) Å and III is monoclinic, P2₁/n, a = 9.387(2) Å, b = 6.710(2) Å, c = 21.513(6) Å, β = 97.18(3)°.     

Molybdenum(VI) network polymers based on anion–π interaction and hydrogen bonding: Synthesis, crystal structures and oxidation catalytic application

A crystallographic investigation of anion–π interactions and hydrogen bonds on the preferred structural motifs of molybdenum(VI) complexes has been carried out. Two molybdenum(VI) network polymers MoO₂F₄·(Hinca)₂ (1) and MoO₂F₃(H₂O)·(Hinpa) (2), where inca = isonicotinamide and inpa = isonipecotamide, have been synthesized, crystallographically characterized and successfully applied to alcohol oxidation reaction. Complex 1 crystallizes in the monoclinic space C2/c: a = 16.832(3) Å, b = 8.8189(15) Å, c = 12.568(2) Å, β = 118.929(3)°, V = 1560.1(5) Å³, Z = 4. Complex 2 crystallizes in the triclinic space P-1: a = 5.459(2) Å, b = 9.189(4) Å, c = 12.204(5) Å, α = 71.341(6)°, β = 81.712(7)°, γ = 77.705(7)°, V = 564.8(4) Å³, Z = 2. Complex 1 consists of hydrogen bonding and anion–π interactions, both of which are considered as important factors for controlling the geometric features and packing characteristics of the crystal structure. The geometry of the sandwich complex of [MoO₂F₄]²⁻ with two pyridine rings indicates that the anion–π interaction is an additive and provides a base for the design and synthesis of new complexes. For complex 2, the anions and the protonated inpa ligands form a 2D supramolecular network by four different types of hydrogen contacts (N–HF, N–HO, O–HF and O–HO). The catalytic ability of complexes 1 and 2 has also been evaluated by applying them to the oxidation of benzyl alcohol with TBHP as oxidant.     

Synthesis, crystal structures, phase transition characterization and thermal decomposition of a new dabcodiium hexaaquairon(II) bis(sulfate): (C6H14N2)[Fe(H2O)6](SO4)2

The crystal structures of 1,4-diazabicyclo[2.2.2]octane (dabco)-templated iron sulfate, (C₆H₁₄N₂)[Fe(H₂O)₆](SO₄)₂, were determined at room temperature and at −173 °C from single-crystal X-ray diffraction. At 20 °C, it crystallises in the monoclinic symmetry, centrosymmetric space group P2₁/n, Z=2, a=7.964(5), b=9.100(5), c=12.065(5) Å, β=95.426(5)° and V=870.5(8) ų. The structure consists of [Fe(H₂O)₆]²⁺ and disordered (C₆H₁₄N₂)²⁺ cations and (SO₄)²⁻ anions connected together by an extensive three-dimensional H-bond network. The title compound undergoes a reversible phase transition of the first-order at −2.3 °C, characterized by DSC, dielectric measurement and optical observations, that suggests a relaxor–ferroelectric behavior. Below the transition temperature, the compound crystallizes in the monoclinic system, non-centrosymmetric space group Cc, with eight times the volume of the ambient phase: a=15.883(3), b=36.409(7), c=13.747(3) Å, β=120.2304(8)°, Z=16 and V=6868.7(2) ų. The organic moiety is then fully ordered within a supramolecular structure. Thermodiffractometry and thermogravimetric analyses indicate that its decomposition proceeds through three stages giving rise to the iron oxide.     

A 3D porous indium(III) coordination polymer involving in-situ ligand synthesis

The hydrothermal reaction of In³⁺ and 1,2,4-benzenetricarboxylic acid with the presence of piperazine leads to the generation of a novel 3D porous coordination polymer, [H₃O][In₂(btc)(bdc)(OH)₂]·5.5H₂O (1), (btc=1,2,4-benzenetricarboxylate, bdc=1,4-benzenedicarboxylate). Compound 1 crystallizes in orthorhombic space group Pbca with a=16.216(7) Å, b=13.437(6) Å, c=31.277(14) Å, and Z=8. It is interesting to find that the in-situ decarboxylation reaction of 1,2,4-benzenetricarboxylate (btc) partially transformed into 1,4-benzenedicarboxylate (bdc) occurs. The 16 indium(III) centers were linked by four btc, four bdc and two μ₂-OH ligands to form a box-girder. The adjacent box-girders are further connected by the bdc and btc ligands to generate a novel porous metal–organic framework containing nanotubular open channel with a cross-section of approximately 11.5×11.3 Å². The micropores are occupied by lattice water molecules, and the solvent-accessible volume of the unit cell was estimated to be 3658.6 Å³, which is approximately 53.7% of the unit-cell volume (6815.4 Å³).     

Flux synthesis of (3,4)-connected zinc phosphites with different framework topologies

Two three-dimensional open-framework zinc phosphites, H₂aem·Zn₃(HPO₃)₄·0.5H₂O (1) and H₂apm·Zn₃(HPO₃)₄ (2), have been synthesized by a phosphorous acid flux method, where aem=4-(2-aminoethyl)morpholine and apm=4-(3-aminopropyl)morpholine. Compound 1 crystallizes in the monoclinic system, P2₁/c, a=9.5852(7) Å, b=20.3941(8) Å, c=10.5339(8) Å, β=94.125(9)°, V=2053.8(2) Å³, Z=4, R₁=0.0319, wR₂=0.0628. Compound 2 crystallizes in the monoclinic system, P2₁/n, a=8.589(2) Å, b=14.020(3) Å, c=16.606(3) Å, β=97.190(8)°, V=1983.9(7) Å³, Z=4, R₁=0.0692, wR₂=0.1479. Both compounds are based on (3,4)-connected networks with 8- and 12-ring channels, which are constructed from Zn₃(HPO₃)₄ clusters as the same secondary building units. These inorganic clusters are spatially organized by different structure-directing agents into different three-dimensional frameworks.     

A two-dimensional bimetallic oxide constructed from ζ-octamolybdate clusters and Ag(I)-tpyprz cationic polymer components (tpyprz = tetra-2-pyridylpyrazine)

The hydrothermal reaction of Na₂MoO₄, Ag(CH₃CO₂), tetra-2-pyridylpyrazine (tpyprz), HF and water at 170 °C for 48 h yields [ Ag₄(tpyprz)₂(H₂O) Mo₈O₂₆] (1) as colorless plates. The structure of 1 is a two-dimensional network, constructed from Ag₄(tpyprz)₂(H₂O) ⁴ⁿ⁺_n chains linked through ζ- clusters. The chains exhibit three distinct Ag(I) environments: a four coordinate AgN₄ site, a three coordinate AgN₂O_aqua site, and four coordinate AgN₃O_oxo site which links to the molybdate cluster. Each cluster is connected by bridging oxo-groups to two silver/tpyprz chains to form the network architecture. Crystal data: C₂₄H₁₇Ag₂Mo₄N₆O_13.5, fw 1204.94, orthorhombic Pccn, a=20.8234(9) Å, b=14.5076(6) Å, c=20.3537(9) Å, V=6148.9(5) Å³, Z=8, D_calc=2.603 g cm⁻³.     

Syntheses and characterization of two oxoborates, (Pb3O)2(BO3)2MO4 (M=Cr, Mo)

Two oxoborates, (Pb₃O)₂(BO₃)₂MO₄ (M=Cr, Mo), have been prepared by solid-state reactions below 700 °C. Single-crystal XRD analyses showed that the Cr compound crystallizes in the orthorhombic group Pnma with a=6.4160(13) Å, b=11.635(2) Å, c=18.164(4) Å, Z=4 and the Mo analog in the group Cmcm with a=18.446(4) Å, b=6.3557(13) Å, c=11.657(2) Å, Z=4. Both compounds are characterized by one-dimensional chains formed by corner-sharing OPb₄ tetrahedra. BO₃ and CrO₄ (MoO₄) groups are located around the chains to hold them together via Pb–O bonds. The IR spectra further confirmed the presence of BO₃ groups in both structures and UV–vis diffuse reflectance spectra showed band gaps of about 1.8 and 2.9 eV for the Cr and Mo compounds, respectively. Band structure calculations indicated that (Pb₃O)₂(BO₃)₂MoO₄ is a direct semiconductor with the calculated energy gap of about 2.4 eV.     

A B3LYP study on counterpoise-corrected geometry optimizations for hydrated complexes of [K(H2O)n] and [Na(H2O)n]

We report the basis set dependencies and the basis set superposition errors for the hydrated complexes of K⁺ and Na⁺ ions in relation to the recent studies of the KcsA potassium channel. The basis set superposition errors are estimated by the geometry optimizations at the counterpoise-corrected B3LYP level. The counterpoise optimizations alter the hydration distances by about 0.02–0.03 Å. The enthalpies and free energies for K⁺ + n(H₂O) → [K(H₂O)_n]⁺ and Na⁺ + n(H₂O) → [Na(H₂O)_n]⁺ (n = 1–6) are compared between the theoretical and experimental values. The results show that the addition of diffuse functions to K, Na, and O species are effective. However, it is also found that the counterpoise corrections using diffuse functions work so as to underestimate the free energies for the complexes with increasing the hydration number. The stabilization energies in aqueous solution are larger for a Na⁺ ion than for a K⁺ ion, suggesting the contributions of their dehydration processes to the ion selectivity of the KcsA potassium channel. The changes in coordination distance between the isolated [K(H₂O)₈]⁺ and the [K(H₂O)₈]⁺ in the KcsA potassium channel indicate the importance of hydrogen bondings between the first hydration shell and the outer hydration shells.     

Investigation on the complex of diperoxovanadate with picolinamide

A novel diperoxovanadate complex NH₄[OV(O₂)₂(picolinamide)]·H₂O was synthesized from aqueous solution under physiological conditions. The solution structure of the complex was characterized by multinuclear (¹H, ¹³C, ¹⁴N, and ⁵¹V), variable temperature as well as two-dimensional (DOSY) NMR techniques in the interaction system of NH₄VO₃/H₂O₂/picolinamide at room temperature. The crystal structure of the complex was determined at 223 K by single-crystal X-ray diffraction method. It belongs to the monoclinic space group P21/c with a = 7.323(3) Å, b = 14.255(7) Å, c = 10.022(5) Å, β = 99.524(9)°, V = 1031.7(8) Å³, and Z = 4. The crystal is composed of ammonium ions, picolinamide oxodiperoxovanadate(V) ions, and water molecules, which are held together by ionic and hydrogen bond forces. The species [OV(O₂)₂(picolinamide)]⁻ is seven-coordinated with a distorted pentagonal bipyramidal geometry both in solution and in crystal.     

Hydrothermal Synthesis and Crystal Structure of [(CH3NH3)1.03K2.97]Sb12S20·1.34H2O

A novel thioantimonate(III) [(CH₃NH₃)_1.03K_2.97]Sb₁₂S₂₀·1.34H₂O was synthesized hydrothermally. It crystallizes in space groupP , witha=11.9939(7) Å,b=12.8790(8) Å,c=14.9695(9) Å,α=100.033(1)°,β=99.691(1)°,γ=108.582(1)°,V=2095.3(2) ų, andZ=2. The structure is determined from single crystal X-ray diffraction data collected at room temperature and refined toR(F)=0.037. In the crystal structure, each Sb(III) atoms has short bonds (2.37–2.58 Å) to three S atoms. The pyramidal [SbS₃] groups share common S atoms forming two types of centrosymmetric [Sb₁₂S₂₀] rings with the same topology. These rings are interconnected by weaker Sb–S bonds (2.92–3.29 Å) into 2-dimensional layers. Adjacent layers are parallel with K⁺and CH₃NH⁺₃ions and H₂O molecules located between them. Variation of bond valence sums calculated for the Sb(III) cations is found to be correlated with the coordination geometry. This is interpreted as due to the stereochemical activity of their lone electron pairs.     

Processes of dissociative electron capture by 20-hydroxyecdysone molecules

The peculiarities of dissociative electron capture by 20-hydroxyecdysone molecules with the formation of fragment negative ions were studied. In the region of high electron energies (5–10 eV), processes of skeleton bond rupture are accompanied by the elimination of H₂O and H₂ molecules. In the region of thermal energies of electrons (≈0 eV), the mass spectrum is formed mainly by the [M−nH₂O]^.− (n=1–3) and [M−H₂−nH₂O]^.− (n=0−3) ions that are generated exclusively by the rearrangement. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 709–712, April, 2000.     

Structure and properties of Y5Mo2O12 and Gd5Mo2O12: Mixed valence oxides with structurally equivalent molybdenum atoms

Crystals of Ln₅Mo₂O₁₂ (Ln = Y, Gd) were grown by electrochemical reduction of alkali-molybdate/rare-earth oxide melts at 1075–1100°C. A single crystal of Y₅Mo₂O₁₂, used for structure determination, was found to be monoclinic with a = 12.2376(7) Å, b = 5.7177(8) Å, c = 7.4835(5) Å, β = 108.034(5)°, and Z = 2. Although the structure was refined in space group C2/m, the true space group appears to be P2₁/m. In Y₅Mo₂O₁₂, rutile-like sheets of edge-shared MoO₆ chains linked by YO₆ octahedra are interconnected with YO₇ monocapped trigonal prisms. The Mo atoms in the chains have alternating distances of 2.496 and 3.221 Å and in that respect are similar to MoO₂. However, in contrast to metallic MoO₂ both the Y and Gd compounds are n-type semiconductors with room temperature resistivities of the order of 10³ ohm-cm. Magnetic susceptibility measurements confirm the presence of one unpaired electron per Mo₂ unit. The semiconducting behavior can be explained in terms of an unfavorable bridging oxygen coordination which prevents electron delocalization through metal-oxygen pi bonding as in MoO₂.     

Isolation of p-tricyanovinylphenyldicyanomethide ion via a [2+2] cycloaddition of 7,7,8,8-tetracyanoquinodimethane (TCNQ) molecules

In the presence of CoCl₂·6H₂O and dppm (bis(diphenylphosphino) methane), the reaction of TCNQ (7,7,8,8-tetracyanoquinodimethane) molecules by [2+2] cycloaddition forms a p-tricyanovinylphenyldicyanomethide ion (PCQ⁻), which has been obtained as one anion unit in one new compound [Co(dppmdo)₃][PCQ⁻]₂·H₂O 1 (dppmdo = bis(diphylphospine oxide) methane). Its structure was determined by X-ray crystallography: 1 crystallizes in with a = 14.174(3) Å, b = 19.553(4) Å, c = 19.776(4) Å, α = 112.72(3)°, β = 95.43(3)°, γ = 110.79(3)°, and Z = 2. It was characterized by IR spectra, UV–Vis spectra, and cyclic voltammogram. Magnetic properties indicate that no magnetic coupling between PCQ⁻ and [Co(dppmdo)₃]²⁺ unit.     

The crystal and molecular structure of potassium aquapentachloroiridate(III) and the H, C, N NMR coordination shifts in iridium(III) chloride complexes with 2,2′-bipyridine or 1,10-phenanthroline

The crystal and molecular structure of potassium aquapentachloroiridate(III) (K₂[Ir(H₂O)Cl₅]) was reported. The [Ir(H₂O)Cl₅]²⁻ anions are nearly octahedral, the axial Ir–Cl bond (2.322(2) Å) being shorter than the equatorial ones (2.346(2)–2.360(2) Å); the Ir–O bond length is 2.090(4) Å. Ir(III) chloride complexes with 2,2′-bipyridine (LL = bpy) or 1,10-phenanthroline (LL = phen), of the general formulae K[Ir(LL)Cl₄] and cis-[Ir(LL)₂Cl₂]Cl, were studied by far-IR and ¹H–¹³C, ¹H–¹⁵N HMBC/HMQC/HSQC–NMR. High-frequency ¹H NMR coordination shifts (Δ^1H_coord = δ^1H_complex − δ^1H_ligand; max. ca. +1 ppm) were noted for [Ir(LL)Cl₄]⁻ anions, while for cis-[Ir(LL)₂Cl₂]⁺ cations they had variable sign and magnitude (max. ca. ±1 ppm); they were dependent on the proton position, being mostly expressed for the nitrogen-adjacent hydrogens (H(6) for bpy, H(2) for phen). ¹³C NMR signals were high-frequency shifted (by max. ca. 8 ppm), whereas all ¹⁵N nuclei were shifted to the lower frequency (by ca. 105–120 ppm). The experimental ¹H, ¹³C, ¹⁵N NMR chemical shifts were reproduced by semi-empirical quantum-chemical calculations (B3LYP/LanL2DZ+6-31G^**//B3LYP/LanL2DZ+6-31G*).     

Reaction of hexanuclear niobium and tantalum halide clusters with mercury(II) halides. II. Semiconducting compounds with [Ta6Cl12] unit

A series of paramagnetic clusters of the composition [(Ta₆Cl₁₂)Cl(H₂O)₅][HgX₄] · 9H₂)O (X = Cl, Br, I) has been prepared by the reaction of [Ta₆Cl₁₂]³⁺ methanol-water solutions with HgX₂ and NaX halides. The structure of [(Ta₆Cl₁₂)Cl(H₂O)₅][HgBr₄] · 9H₂O has been solved by X-ray diffraction in the cubic space group Fd 3m. Crystal data: a = 20.036(2) Å, V = 8043.0(1) ų, Z = 8, R = 0.048 (R_w = 0.051). The structure is composed of an octahedral [(Ta₆Cl₁₂)Cl(H₂O)₅]²⁺ cluster cation, tetrahedral [HgBr₄]²⁻ anion and crystal water molecules. The 2mm symmetry of the octahedron is reduced by the statistical distribution of the five water molecules, O(1), and chlorine, Cl(2), at the terminal coordination sites. Thus, the distances Ta-O(1) and Ta-Cl(2) are averaged to the value of 2.32(2) Å. The Ta-Ta and Ta-Cl(1) bond distances are 2.911(1) Å and 2.440(3) Å, respectively, whereas the Hg-Br bond distance is 2.564(3) Å. The cluster [(Ta₆Cl₁₂)Cl(H₂O)₅][HgBr₄] · 9H₂O is semiconducting with two levels governing conductivity with respective activation energies, E_al = 0.24 eV and E_a2 = 0.17 eV.     

Single-crystal characterization of Co7(OH)6(H2O)3(C4H4O4)47H2O; A new cobalt succinate identified through high-throughput synthesis

A new form of cobalt succinate has been discovered using high-throughput methods and its structure was solved by single crystal X-ray diffraction. Co₇(C₄H₄O₄)₄(OH)₆(H₂O)₃7H₂O crystallizes in the monoclinic space group P2₁/c with cell parameters: a=7.888(2) Å, b=19.082(6) Å, c=23.630(7) Å, β=91.700(5)°, V=3555(2) Å³, R₁=0.0469. This complex structure, containing 55 crystallographically distinct non-hydrogen atoms, is compared to the previously reported nickel phase, characterized using ab initio structure solution from synchrotron powder diffraction data.     

Assembled synthesis of luminescent mono/double‐layered 2D and 3D Zn (II)‐based coordination polymers tuned by flexible bis (pyridyl)propane‐1,2‐diamines and diverse organic dicarboxylates

Six mono/double‐layered 2D and three 3D coordination polymers were synthesized by a self‐assembly reaction of Zn (II) salts, organic dicarboxylic acids and L1/L2 ligands. These polymeric formulas are named as [Zn(L1)(C₄H₂O₄)_0.5 (H₂O)]_n·0.5n(C₄H₂O₄)·2nH₂O ( 1 ), [Zn₂(L2)(C₄H₂O₄)₂]_n·2nH₂O ( 2 ), [Zn(L1)(m‐BDC)]_n ( 3 ), [Zn₂(L2)(m‐BDC)₂]_n·2nH₂O ( 4 ), [Zn₃(L1)₂(p‐BDC)₃(H₂O)₄]_n·2nH₂O ( 5 ), [Zn₂(OH)(L2) (p‐BDC)_1.5]_n ( 6 ), [Zn₂(L1)(p‐BDC)₂]_n·5nH₂O ( 7 ), [Zn₂(L2)(p‐BDC)₂]_n·3nH₂O ( 8 ) and [Zn₂(L1)(C₄H₄O₄)_1.5(H₂O)]_n·n(ClO₄)·nH₂O ( 9 ) [L1 = N,N′‐bis (pyridin‐4‐ylmethyl)propane‐1,2‐diamine, L2 = N,N′‐bis (pyridin‐3‐ylmethyl)propane‐1,2‐ diamine, m‐BDC^2? = m‐benzene dicarboxylate, p‐BDC^2? = p‐benzene dicarboxylate]. Meanwhile, these polymers have been characterized by elemental analysis, infrared, thermogravimetry (TG), photoluminescence, powder and single‐crystal X‐ray diffraction. Polymers 1–6 present mono‐ and double (4,4)‐layer motifs accomplished by L1/L2 ligands with diverse conformations and organic dicarboxylates, and the layer thickness locates in the range of 5.8–15.0 Å. In three 3D polymers, the L1 and L2 molecules adopt the same cis‐conformations and join adjacent Zn (II) cations together with p‐BDC^2? or succinate, giving rise to different binodal (4,4)‐c nets with (4.5².8³)(4.5³.7²) ( 7 ), pts ( 8 ) topology and twofold interpenetrated binodal (5,5)‐c nets with (3².4⁴.5².6²)(3.4³.5².6⁴) ( 9 ). Therefore, the diverse conformations of the two bis (pyridyl)‐propane‐1,2‐diamines and the feature of different organic dicarboxylate can effectively influence the architectures of these polymers. Powder X‐ray diffraction patterns demonstrate that these bulk solid polymers are pure phase. TG analyses indicate that these polymers have certain thermal stability. Luminescent investigation reveals that the emission maximum of these polymers varies from 402 to 449 nm in the solid state at room temperature. Moreover, 1 , 3 and 5–8 show average luminescence lifetimes from 8.81 to 16.30 ns.     

(C6H16N2)Zn3(HPO3)4H2O: a new layered zinc phosphite templated by diprotonated trans-1,4-diaminocyclohexane

Employing trans-1,4-diaminocyclohexane (trans-1,4-DACH) as a template, a new two-dimensional layered zinc phosphite (C₆H₁₆N₂)Zn₃(HPO₃)₄H₂O (1) has been prepared hydrothermally. Single-crystal X-ray diffraction analysis shows that it crystallizes in the monoclinic space group P2₁/n with a=10.458(2) Å, b=14.720(3) Å, c=13.079(3) Å, β=97.93(3)°, V=1994.1(7) ų, Z=4, R₁=0.0349 (I>2σ(I)) and wR₂=0.0605 (all data). The inorganic layer is built up by alternation of ZnO₄ tetrahedra and HPO₃ pseudo pyramids forming a 4.6.8-net. The sheet is featured by a series of capped six-membered rings. The diprotonated trans-1,4-DACH molecules reside in the interlayer region and interact with the inorganic network through H-bonds.     

Hydrothermal Synthesis and Crystal Structure of Barium Hewettite: BaV6O16·nH2O

Ba analogues of hewettite (CaV₆O₁₆·9H₂O) were synthesized by the hydrothermal methods. The compounds exhibit two phases formulated by BaV₆O₁₆·nH₂O and Ba_1+xV₆O₁₆·nH₂O (x≈0.2,n≈3), and the structure of BaV₆O₁₆·nH₂O has been determined from a single crystal study. It crystallizes in the orthorhombic systemPnmmwitha=12.162(3) Å,b=10.841(4) Å,c=17.035(4) Å, andZ=6 and the structure refinements led toR=0.066 andR_w=0.076 for 1480 reflections withI>3σ(I). The structure is basically analogous to that ofγ-Li_1+xV₃O₈or CaV₆O₁₆·9H₂O, consisting of V₆O₁₆layers and interstitial hydrated Ba atoms. The V₆O₁₆layers stack along thecaxis with 8.518-Å spacing which is half of thecaxis; adjacent layers are mirror images of each other. Ba atoms reside in three kinds of sites with totally different oxygen coordinations. Their interlayer distributions result in another long period along thebaxis which is triple the ordinary 3.6-Å period of the hewettite compounds. This is the first single-crystal structural study of the synthetic hewettite compounds.     

Electrodeposition of Mo-Se thin films from a sulfamatic electrolyte

Mo-Se thin films have been electrodeposited on conducting tin oxide (SnO₂) coated glass substrates from a sulfamatic solution containing Na₂MoO₄ and H₂SeO₃ under potentiostatic conditions. The deposition potential varied from –0.6 V to –0.9 V, at a deposition temperature of 20–40 °C and pH 6.5. X-ray diffraction analysis revealed that the overall composition of the films deposited is consistent with the formation of MoO₂ and MoSe₂. The lattice parameters of the as-deposited MoSe₂ are a=b=3.2340 Å and c=13.2859 Å, which fits a hexagonal structure.