Yukiyoshi Sasaki

Crystal Structures and Electrical Properties of BEDT-TTF Coeipounds

Abstract The crystal structure and the electrical resistivities of BEDT-TTF compounds are reported. The most prominent feature of the crystal structure is the side-by-side array of BEDT-TTF molecules. The steric effects of the ethylene groups prevent the infinite stacking of the molecules. The electrical properties and the change in the X-ray diffraction patterns of β-(BEDT-TTF)2PF6 suggest that β-(BEDT-TTF)2PF6 is a one-dimensional conductor along the transverse direction. A simple band calculation indicates that (BEDT-TTF)2Cl04(C2H3C13) 0.5 is a two-dimensional semimetal. (BEDT-TTF)3(C104)2 shows a metal-insulator transition at 170 K, which is consistent with the one-dimensional band structure of this compound.

The Hofman-type clathrate: M(NH3)2M′(CN)4 . 2G

Abstract A series of clathrates with the general formula M(NH3)2M′(CN)4.2G were prepared. Their structures have been ascertained by powder X-ray diffractometry to be similar to that of Hofmanns clathrate Ni(NH3)2Ni(CN)4.2C6H6. The variation in the lattice constants of the tetragonal unit cells can be correlated with the change in the bond length between the metal, M, at the octahedral site and the nitrogen of the cyanide and in that between the metal, M′, at the square-planar site and the carbon of the cyanide, and with the change of the size of the guest molecules. Their infrared spectra have been interpreted in terms of the weak host-guest interaction depending on the M′, and as being almost independent of the change in the M.

Transport properties of ((CH3)4N) (Ni(dmit)2)2: A new organic superconductor

Abstract Transport properties of ((CH 3 ) 4 N) (Ni(dmit) 2 ) 2 crystals are studied in the temperature region from 300 to 1.5 K under hydrostatic pressure up to 15 kbar. A resistivity jump at around 100 K and a sharp rise of resistivity below 20 K are characteristic of this crystal. Hydrostatic pressure reduces both anomalies. In the sample where the low temperature anomaly was suppressed by high pressure, we have observed an onset of a superconducting transition under 3.2 kbar at 3.0 K. The transition temperature becomes high with increasing pressure. At 7 kbar, we find T c = 5.0 K .

Peroxopolytungstic acids synthesized by direct reaction of tungsten or tungsten carbide with hydrogen peroxide

Synthese de W-IPA par reaction de W metallique avec H 2 O 2 et de CW-HPA par reaction de WC avec H 2 O 2 . Spectres Raman et RMN

Preparation of chelate ylide ligands and their palladium(II) and platinum(II) halide complexes

Keto-stabilized mono-ylides of 1,2-bisdiphenylphosphinoethane and bisdiphenylphosphinomethane, Ph2P(CH2)nP+(Ph)2C-HC(O)R (Ph  C6H5; n  1 or 2; R  C6H5, CH3 or OCH3), and their palladium(II) and platinum(II) halide complexes were prepared and characterized by means of infrared, 1H and 31P NMR spectra. The chelate ylide ligands coordinate to the metal through the ylide carbon and phosphine phosphorus forming a six or five-membered chelate ring. The stability of the MC(ylide) bonding is discussed on the basis of the results of the reaction of the complexes with pyridine.

Molecular designing analysis of a new superconducting metal dithiolene complex

Abstract The map of the intermolecular overlap integrals(S) of the lowest unoccupied molecular orbital(LUMO) of Ni(dmit) 2 was calculated by varying the intermolecular configuration parameters in order to examine the dimensionality of the electronic band structure of the molecular conductors based on Ni(dmit) 2 . Despite the similarity of the molecular structure between Ni(dmit) 2 and BEDT-TTF, the intermolecular transverse interaction of Ni(dmit) 2 becomes very weak. Although the crystal structure of a new molecular superconductor (TTF)[Ni(dmit) 2 ] 2 exhibits the three-dimensional (3-D) sulfur network, its tight-binding band calculation gives a strongly 1-D band.

Crystal and electronic structures of new molecular conductors tetramethylammonium and tetramethylarsonium complexes of Pd(dmit)2

The synthesis, structural characterization and electrical conductivity measurements of α-,β-[(CH3)4N][Pd(dmit)2]2 and [(CH3)4As][Pd(dmit)2]2 are reported. They have similar crystal structures made of stacked Pd(dmit)2 dimers. The mode of the intra-dimer molecular overlapping is that of the eclipsed type. Pd atoms deviate from the planes formed by ligand S atoms by 0.07–0.08 A to approach to each other. Simple tight-binding band calculations were made on these three Pd(dmit)2 salts. Each energy band is made up of two energy branches separated by a large mid-gap. The lower energy branch is a narrow half-filled band which seems to be consistent with the weakly metallic or semiconducting behaviour of these compounds around room temperature.

The structure of catena-μ-ethylenediaminecadmium(II) tetracyanoniccolate(II) dibenzene clathrate: Cd(en)Ni(CN)4.2C6H6

Abstract The crystal structure of Cd(en)Ni(CN) 4 · 2C 6 H 6 was determined by the single crystal X-ray diffraction method. The crystal belongs to the tetragonal system with space group of P4/m, a = 7.675±0.003 A, c = 8.056±0.010 A, and Z = 1 (D m = 1.69, D c = 1.72). The structure was solved by the Fourier method and refined by the block-diagonal least-squares method to an R -value of 0.089 for 619 reflection data. The cadmium atoms and the nickel atoms are linked cross-wise with the cyanide anions on the (001) plane to form the layers of the polymeric metal cyanide complex [CdNi(CN) 4 ] ∞ , and the layers are stacked along the c-axis. Each ethylenediamine molecule bridges between the cadmium atoms in the layers to make a three-dimensional host lattice. The benzene molecules are enclathrated in the cavities formed by the host lattice. The electron density for each nitrogen atom of the ethylenediamine molecule was found to be distributed over a torus about the CdCd axis. This fact and the 1 H-NMR data support the rotation of the ethylenediamine molecule about the axis at room temperature.

The crystal structure and ESR studies of diamminecopper(II) tetracyanoniccolate(II) dibenzene clathrate: Cu(NH3)2Ni(CN)4.2C6H6

Abstract The crystal structure of Cu(NH 3 ) 2 Ni(CN) 4 .2C 6 H 6 was determined by three-dimensional X-ray methods. The crystal is tetragonal with the dimensions of a = 7.345 A and c = 16.519 A, and the space group is P4/mcc ( Z = 2). Reflection data were collected with an automatic four circle diffractometer and monochromatized Mo Kα radiation. The structure was solved by the heavy-method and was refined by the block-diagonal least-squares method for 690 independent reflections to a final R-index of 0.068. The copper ions and the nickel ions are linked crosswise with the cyanide anions to form a polymeric two-dimensional metal complex network, and the benzene molecules are trapped among the layers of the networks. This host lattice structure is similar to those of the other Hoffmann-type clathrates, Ni(NH 3 ) 2 Ni(CN) 4 . 2C 6 H 6 and Cd(NH 3 ) 2 Ni(CN) 4 . 2C 6 H 6 , but the c -axis of the cell is doubled due to different orientation of the benzene molecules in alternate guest layers. The copper(II) ion takes a compressed tetragonal coordination with the four nitrogen atoms of the cyanide anions in the (001) plane (the Cu-N distance, 2.20 A) and with the two nitrogen atoms of the ammonia molecules of the [001] axis at the compressed apical positions (the Cu-N distance, 2.05 A). The ESR spectra of the magnetically dilute single crystal of (Cd, Cu)(NH 3 ) 2 Ni(CN) 4 . 2C 6 H 6 can be interpreted in terms of A 1g symmetry of the electronic ground state of the copper(II) ion in the compressed tetragonal environment which was previously concluded from the spectra of the polycrystalline samples.

Structure of the hydrated potassium hexamolybdate complex of hexaoxacyclooctadecane (18-crown-6)

(C 12H2406)2 . K2M06019. H20, orthorhombic, P2~2121, a = 11.678 (3), b = 11.361 (3), c = 35.84 (1) A, U = 4755 (2)/~3, Z = 4, D x = 2 . 1 0 1 M g m -3, g = 1.77 mm -1 (for Mo Ka). A Mo6029 anion is located between two crown-complex cations forming a sandwich structure. The sandwich structures connect with each other through a water molecule. The water molecule is strongly linked to two K + cations by an ion-dipole interaction. Introduction. The merits of crown complexes in the structural study of polyanions have been described in a preceding paper (Nagano, 1979). Following the structural study of (C12H240~) 2. K2MoO 4. 5H20, in which the MoO~anion is a precursor of polymolybate anions, a series of 18-crown-6 complexes of X2Mo6019 (X = Na, K, Rb and NH4) have been prepared and (CI2H2406)2.K2Mo6019. H20 has been subjected to Xray study. A yellow precipitate was obtained from an aqueous solution of 18-crown-6 and K2MoO 4 heated on a steam-bath for one hour (pH = 1.0; 18-crown6 : K2MoO 4 = 1 : 3). Repeated recrystallization of the precipitate from CH3CN gave lemon-yellow crystals. The intensities of the reflections were measured from a crystal of dimensions 0.35 x 0.40 x 0.40 mm with a Rigaku automatic four-circle diffractometer (graphite monochromator, Mo Ka radiation). The to-scan method was used because of the long c axis. Three reference reflections were measured every 50 reflections; no significant changes were observed over the period of data collection. Intensities of reflections from crystals of polymolybdate salts with a large organic ion as a counter cation are generally weak. The intensities of 3112 independent reflections [20 3a(IFol )] were adopted for the structure determination. The structure was solved by the heavy-atom method and refined by the block-diagonal least-squares technique for non-hydrogen atoms. Anisotropic temperature factors were used for all non-hydrogen atoms. The H atoms of 18-crown-6 molecules were included in the refinement in their idealized positions ( C H = 1.00 A, H C H = 109.47 °, B = 5.0 /~2). The atomic scattering factors and corrections for anomalous dispersion were taken from International Tables for X-ray Crystallography (1974). The function minimized was ~ w(IFol -IFcl) 2, where w = 0.7 for IFol 50.0 and w = 1.0 otherwise. The R value (R = Y wllFol IFcll/~ wlFol) was 0.045. The atomic coordinates are listed in Table 1. The sandwich structure of (CI2H2406)2.K2Mo6019 is shown in Fig. 1. A view of the crystal structure along the b axis is shown in Fig. 2.* * Lists of structure factors, anisotropic thermal parameters and H-atom coordinates have been deposited with the British Library Lending Division as Supplementary Publication No. SUP 34515 (27 pp.). Copies may be obtained through The Executive Secretary, International Union of Crystallography, 5 Abbey Square, Chester CH 1 2HU, England. la0~,,-60~ v~0132la-c,~-6(2) Fig. 1. The sandwich structure of (CI2H2406)2.K2Mo6OIg. The vibration ellipsoids are drawn at the 30% probability level (Johnson, 1965). Aq I is related to Aq by the symmetry of the twofold screw axis parallel to the c axis.