Novel transition metal oxalatophosphates with a two-dimensional honeycomb structure: (H3TREN)[M2(HPO4)(C2O4)2.5] x 3H2O (M = Mn(II) and Fe(II), TREN = tris(2-aminoethyl)amine)

Two new layered transition metal oxalatophosphates, (H(3)TREN)[M(2)(HPO(4))(C(2)O(4))(2.5)].3H(2)O (M = Mn(II) and Fe(II)), have been synthesized by hydrothermal methods in the presence of a structure-directing organic amine, tris(2-aminoethyl)amine, and characterized by single-crystal X-ray diffraction and magnetic susceptibility. They are the first metal oxalatophosphates which adopt a two-dimensional honeycomb structure with the organic cations and water molecules intercalated in between. Within a layer, there are 12-membered pores made from 6 Mn, 1 phosphate, and 5 oxalate units. Measurements of field dependence of magnetization and variable-temperature susceptibilities under different fields were performed on a polycrystalline sample of the manganese compound. The results indicate a phase transition from a paramagnetic to an antiferromagnetic coupled state at about 12 K. Crystal data for the manganese compound follow: triclinic, space group Ponemacr; (No. 2), a = 8.8385(6) A, b = 9.0586(6) A, c = 16.020(1) A, alpha = 77.616(1) degrees, beta = 83.359(1) degrees, gamma = 68.251(1) degrees, and Z = 2. Crystal data for the iron compound are the same as those for the manganese compound except a = 8.7776(9) A, b = 8.9257(9) A, c = 15.884(2) A, alpha = 78.630(2) degrees, beta = 84.018(2) degrees, and gamma = 67.372(2) degrees.     

Novel vanadium(V) compounds with a layer structure: synthesis,crystal structures,and solid state NMR spectroscopy of [(VO(2))(2)(4,4'-bpy)(0.5)(4,4'-Hbpy)(XO(4))] x H(2)O (X = P and As)

A novel vanadium(V) phosphate and the arsenate analogue, [(VO(2))(2)(4,4'-bpy)(0.5)(4,4'-Hbpy)(XO(4))].H(2)O (X = P, As; bpy = bipyridine), have been synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. They are the first structurally characterized compounds in the vanadium(V)/4,4'-bpy/phosphate (or arsenate) systems. The two compounds are isostructural and crystallize in the triclinic space group P macro (No. 2) with a = 7.9063(3) A, b = 10.2201(4) A, c = 12.1336(5) A, alpha = 113.4652(7) degrees, beta = 95.7231(7) degrees, gamma = 94.4447(7) degrees, and Z = 2 for the phosphate, and a = 7.8843(6) A, b = 10.3686(7) A, c = 12.2606(9) A, alpha = 113.464(1) degrees, beta = 95.560(1) degrees, gamma = 94.585(1) degrees, and Z = 2 for the arsenate. The structure consists of phosphate-bridged vanadium(V) double chains linked through 4,4'-bpy ligands to form a sheet with the monoprotonated 4,4'-Hbpy(+) ligand being coordinated to the metal atom as a pendent group. The (1)H MAS NMR spectrum exhibits four resonances at 14.2, 9.5, 7.2, and 3.7 ppm with an intensity ratio close to 1:6:6:2, corresponding to three different types of protons in 4,4'-bpy and 4,4'-Hbpy(+) and one type of protons in H(2)O. The peak at 14.2 ppm can be assigned to the proton bonded to the pyridine nitrogen atom, which confirms the presence of 4,4'-Hbpy(+).     

N(CH2CH2NH3)3][U3O2F13].2H2O: a novel organically templated mixed-valent uranium oxyfluoride with a hybrid network structure

The synthesis and characterization of a novel mixed-valent uranium oxyfluoride is described; the inorganic network consists of 2-D [U(2)F(10)](2)(-) sheets constructed from corner- and edge-sharing U(IV)F(9) tricapped trigonal prisms and 1-D [UO(2)F(3)](-) chains constructed from edge-sharing U(VI)O(2)F(5) pentagonal bipyramids with the organic cations and water molecules between the sheets. This is the first example with a hybrid network structure in the system of uranium fluoride or oxyfluoride. The variable-temperature magnetic susceptibility confirms the oxidation state of the uranium ions. Crystal data follow: C(6)H(25)N(4)O(4)F(13)U(3), monoclinic, space group P2(1) (No. 4); a = 8.6876(4) A, b = 7.3158(4) A, c = 16.3376(8) A, beta = 93.7285(9) degrees , V = 1036.2(2) A(3), and Z = 2.     

Alcohols,ethers, carbohydrates,and related compounds. II. The anomeric effect

The anomeric effect has been studied for a variety of compounds using the MM4 force field, and also using MP2/6-311++G(2d,2p) ab initio calculations and experimental data for reference purposes. Geometries and energies, including conformational, rotational barriers, and heats of formation were examined. Overall, the agreement of MM4 with the experimental and ab initio data is good, and significantly better than the agreement obtained with the MM3 force field. The anomeric effect is represented in MM4 by various explicit terms in the force constant matrix. The bond length changes are accounted for with torsion-stretch elements. The angle changes are accounted for with torsion-bend elements. The energies are taken into account with a number of torsional terms in the usual way. A torsion-torsion interaction is also of some importance. With all of these elements included in the calculation, the MM4 results now appear to be adequately accurate. The heats of formation were examined for a total of 12 anomeric compounds, and the experimental values were fit by MM4 with an RMS error of 0.42 kcal/mol.     

Scanning tunnelling microscope studies of growth of RuO2（110） thin layer on Ru（0001）

This paper reports that the growth of RuO_x(110) thin layer growth on Ru(0001) has been investigated by means of scanning tunnelling microscope (STM). The STM images showed a domain structure with three rotational domains of RuO_x(110) rotated by an angle of 120℃. The as-grown RuO_x(110) thin layer is expanded from the bulk-truncated RuO_x(110) due to the large mismatch between RuO_x(110) and the Ru(0001) substrate. The results also indicate that growth of RuO_x(110) thin layer on the Ru(0001) substrate by oxidation tends first to formation of the Ru-O (oxygen) chains in the [001] direction of RuO_x(110).     

Vibrational spectrum of RbVOPO4

The infrared and Raman laser spectra of RbVOPO₄ were recorded and briefly discussed with the aid of factor group analysis. Some comparisons with the spectra of related materials were also made.     

Directional hydrogen bonding in the MM3 force field: II

Extensive calculations on hydrogen bonded systems were carried out using the improved MM3 directional hydrogen bond potential. The resulting total function was reoptimized. Comparisons of the hydrogen bonding potential function from ab initio calculations (MP2/6-31G**); the original MM3(89); and the reoptimized MM3 force field MM3(96), for a variety of C, N, O, and Cl systems including the formamide dimer and formamide–water complex, are described herein. Hydrogen bonding is shown to be a far more complicated and ubiquitous phenomenon than is generally recognized. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 1001–1016, 1998     

Synthesis, crystal structure, and solid-state NMR spectroscopy of a salt-inclusion stannosilicate: [Na3F][SnSi3O9

A salt-inclusion stannosilicate, [Na3F][SnSi3O9], has been synthesized using a flux-growth method and characterized by single-crystal X-ray diffraction. The structure consists of six-membered silicate rings linked via corner sharing by SnIVO6 octahedra to form a 3-D framework that delimits two types of channels. The F atoms and Na atoms are located in the structural channels and form a dimer with the anti-Al2Cl6(g) structure. This stannosilicate adopts a new structure and is the first metal silicate that contains both Na+ and F- ions in the channels. The 19F and 29Si MAS NMR and 23Na MQMAS NMR spectra are consistent with the crystallographic results.     

Rb3In(H2O)Si5O13: a novel indium silicate with a CdSO4-topological-type structure

A novel indium silicate, Rb3In(H2O)Si5O13, has been synthesized using a high-temperature, high-pressure hydrothermal method and characterized by single-crystal X-ray diffraction. The structure consists of five-membered rings of corner-sharing SiO4 tetrahedra connected via corner sharing to four adjacent five-membered rings to form a 3D silicate framework that belongs to the CdSO4 topological type. The InO6 octahedron shares five of its corners with five different SiO4 tetrahedra to form a 3D frame-work that delimits two types of channels to accommodate the rubidium cations. The sixth corner of InO6 is coordinated H2O. The structure is related to that of the titanium silicate ETS-10, and these are the only two metal silicates that have the CdSO4-topological-type structure. In addition, the crystal of Rb3In(H2O)Si5O13 shows an intense second harmonic generation signal. Crystal data: H2Rb3InSi5O14, monoclinic, space group Cc (No. 9), a = 9.0697(5) A, b = 11.5456(6) A, c = 13.9266(8) A, beta = 102.300(1) degrees, V = 1424.8(1) A3, and Z = 4.     

Synthesis and Characterization of ASnOAsO4(A = K and Rb)

Crystals of two alkali-metal tin(IV) arsenates, KSnOAsO₄ and RbSnOAsO₄, were grown from a flux and structurally characterized by single-crystal X-ray diffraction. Crystal data: RSnOAsO₄, orthorhombic, Pna2₁ (No. 33), a = 13.406(3) Å, b = 6.678(1) Å, c = 10.921(2) Å, Z = 8, R = 0.037 for 1173 independent reflections with I > 2.5ó(l); RbSnOAsO₄, as above except a = 13.567(3) Å, b = 6.791( 1) Å, c = 10.891(2) Å, R = 0.035 for 1958 independent reflections. The two compounds are isostructural with the nonlinear optical material KTiOPO₄. The oxygen frameworks of both tin compounds approximate closely to a centrosymmetric arrangement, as indicated from the analysis of atomic coordinates. Second harmonics were generated in powdered RbSnOAsO₄ to confirm the absence of a center of symmetry in the structure.