Classification of electrically conducting ‘electron-transfer’ compounds by crystal structure

Organic and metal-organic electron-transfer solids can be classified by crystal structure, those known to date being divided intohomosoric, in which identical molecules stack infinitely,heterosoric, in which different molecules stack alternately, andnonsoric, non-stacked types. Only homosoric solids have high electrical conductivity.     

Electrical characterization of ion conducting biopolymeric gel complexes

Gum Arabica is a naturally occurring conducting biomaterial biopolymer, its various aspects of electrical and structural characteristics have been investigated in our earlier works. In the present work the ionic gel formation of Gum Arabica and its electro-chemical application were experimentally investigated. Hot concentrated aqueous solution of Gum Arabica with phosphoric acid, minimum 16% of solute, was found to form ionic hydrogel on slow cooling. It consists of polyelectrolyte molecules cross-linked by phosphate ions by chemical bonds into an integrated spatial network in water solvent. The increase in surface to volume ratio shows a gel collapse to provide transparent solid material. Gel formation of Gum Arabica was also studied with chromium and molybdenum oxide as cross-linking agent. The various studies carried out on the mentioned materials to investigate its structural and electrical characteristics are XRD, DSC, SEM and impedance spectroscopy. The said gel was found to provide a good electro-chemical cell with suitable redox pair.     

The synthesis and crystal structures of new trinuclear and hexanuclear nickel complexes with metallodithiolate ligands

Two nickel complexes with metallodithiolate ligands, which can be regarded as the active site models of the acetyl coenzyme A synthase, were prepared and structurally characterized by X-ray crystallography. Reactions of Ni(PPh₃)₂Cl₂ with Ni(bme-dach) [bme-dach = N,N'-bis(mercaptoethyl)-1,4-diazacycloheptane] or Ni(bme-dach^*) [bme-dach^* = N,N'-bis(mercaptoethyl)-1,4-diazacyclohexane] in MeCN in the presence of NH₄PF₆ resulted in the formation of a trinuclear nickel complex {Ni[Ni(bme-dach)]₂}[PF_6-]₂ (1) and a hexanuclear nickel complex {Ni₂[Ni(bme-dach^*)]₄}[PF₆^?]₄ (2). The crystal structure of 1·2MeCN shows a square planar geometry of nickel atom that is coordinated by four sulfur atoms of the metallodithiolate ligands Ni(bme-dach). The crystal structure of 2·4MeCN reveals that each of the two nickel atoms is ligated by four sulfur atoms of the metallodithiolate ligands Ni(bme-dach^*) to form a square planar coordination sphere.     

Some recent new applications of glass technology

Currently, at Corning Glass Works we are involved in several new, interesting applications of glass technology, which have the potential of impacting a wide diversity of applications. Three such areas presently under investigation will be reviewed, viz., molded optics, dental restorative materials, and inorganic paper. The common denominator relating these three examples is the fact that each relies on a unique glass composition as the starting material.

The first development is a special area of glass composition capable of being molded directly into optical elements without grinding and polishing. The second involves a new castable micaceous ceramic dental material derived from special glass compositions for application in several phases of restorative dentistry. Finally, the third development relates to a ceramic paper based upon a mica-like crystal, which is precipitated from glass.

The current status of the technology will be discussed for each in the context of the potential applications.     

Synthesis and crystal structure of thiosemicarbazide complexes of nickel(II) and copper(II)

Thiosemicarbazide complexes of nickel(II) [Ni(TSC)₂](HSal)₂ (I) and copper(II) [Cu(TSC)₂](HSal)₂ (Ia) (TSC is thiosemicarbazide and HSal is a salycilate anion), as well as complexes [Ni(TSC)₂](SO₄) · 2H₂O (II) and [Ni(TSC)₃]Cl₂ · H₂O (III), are synthesized and characterized by IR spectroscopy and X-ray diffraction. Monoclinic crystals I and Ia are isostructural; space group P2₁/n, Z = 2. Crystals II are monoclinic, space group P2₁/m, Z = 2. Crystals III are orthorhombic, space group Pbca, Z = 8. In I and Ia, two planar salycilate anions sandwich a planar centrosymmetric [Ni(TSC)₂]²⁺ cation to form a supermolecule. The cation and anions are additionally bound by hydrogen bonds. Other hydrogen bonds connect supermolecules into planar layers. In structure II, centrosymmetric [Ni(TSC)₂]²⁺ cations are connected by ??-stacking interactions into supramolecular ensembles of a specific type. The ensembles, water molecules, and (SO₄)^2? anions are bound in the crystal via hydrogen bonds. In the [Ni(TSC)₃]²⁺ cation of structure III, ligands coordinate the Ni atom by the bidentate chelate pattern with the formation of five-membered metallocycles. These metallocycles have an envelope conformation unlike those in I and II, which are planar. In III (unlike in analogous complexes), a meridional isomer of the coordination octahedron of the Ni atom is formed. Together with Cl1^? and Cl2^? anions, cations form supermolecules, which are packed into planar layers with a square-cellular structure. The layers are linked by hydrogen bonds formed by crystallization water molecules that are located between the layers.     

Synthesis,spectroscopic characterization of thiosemicarbazone complexes of nickel(II) and X-ray structures of anisaldehyde thiosemicarbazone (ATSZH) and bis(tolualdehyde thiosemicarbazonato)nickel(II)

Complexes of nickel(II) with anisaldehyde (ATSZH), tolualdehyde (TTSZH), and vanillin (VTSZH) thiosemicarbazones have been synthesized and characterized by means of UV-Visible, I.R., Raman,¹H and¹³C NMR spectroscopy. The thiosemicarbazones have been found to exist in the thione form.¹H and¹³C NMR as well as electronic spectral data support a square planar structure for Ni(ATSZ)₂ and Ni(TTSZ)₂ complexes.¹H and¹³C NMR spectra indicate that the structure of Ni(VTSZ)₂ complex differs from the other two nickel(II) complexes and it may possibly consist of mixtures of isomers. The X-ray structures of Ni(TTSZ)₂ and ATSZH were determined: the nickel complex is monoclinic witha=26.412(6),b=12.135(3),c=6.888(1)Å,=95.41(5)°,Z=4,R=0.0647, space groupC2/c. The structure consists of discrete Ni(TTSZ)₂ molecules in which the metal, located on a symmetry centre, is N,S-chelated by two ligands forming two five-term chelate rings. The structure of ATSZH is also monoclinic:a=7.859(1),b=13.481(3),c=10.028(3) Å,=106.32(4)°,Z=4,R=0.0412, space groupP2₁/c. The molecules, connected by NO hydrogen bonds, reveal a considerable tilting of the aromatic ring in respect to the thiourea moiety if compared with the nickel structure.     

Some new bis-1,4 pentazadienes: synthesis and photochemical properties

Abstract

The synthesis of some new bis-1,4-pentazadienes and their photolytic decomposition are described. The uniformity of photolysis reactions is studied by the AD-diagram method. It was found that the photolysis on the later stages does not proceed by the first-order reaction kinetics.     

The conformation of pentaazamacrocyclics. I. Crystal structures of nickel (II) and copper (II) complexes of 1,4,7,11,14-pentaazacycloheptadecane

The crystal structures of [Ni(17-aneN₅)H₂O]Br₂·3H₂O (17-aneN₅=1,4,7,11,14-pentaazacycloheptadecane) and of [Cu(17-aneN₅)]CuBr₄ are reported. Diffraction data using MoK radiation were measured with a CAD-4 diffractometer and the structures refined by full-matrix least squares. The nickel compound has regular octahedral coordination with coordinated water completing the octahedron. The copper is approximately square-pyramidal with an apical Cu-N bond of 2.29(4) Å, compared to a mean bond length of 2.06(2) Å in the basal plane. As a result, the folding of the 17-membered macrocyclic rings is completely different in the two compounds.     

Synthesis and X-ray diffraction study of new uranyl malonate and oxalate complexes with carbamide

Two new malonate-containing uranyl complexes with carbamide of the formulas [UO₂(C₃H₂O₄)(Urea)₂] (I) and [UO₂(C₃H₂O₄)(Urea)₃] (II), where Urea is carbamide, and one uranyl oxalate complex of the formula [UO₂(C₂O₄)(Urea)₃] (III) were synthesized, and their crystals were studied by X-ray diffraction. The main structural units in crystals I are the electroneutral chains [UO₂(C₃H₂O₄)(Urea)₂]_∞ belonging to the crystal-chemical group AT¹¹M₂¹ (A = UO₂²⁺, T¹¹ = C₃H₂O₄^2-, M¹ = Urea) of uranyl complexes. Crystals II and III are composed of the molecular complexes [UO₂(L)(Urea)₃], where L = C₃H₂O₄^2- or C₂O₄^2-, belonging to the crystal-chemical group AB⁰¹M₃¹ (A = UO₂²⁺, B⁰¹ = C₃H₂O₄^2- or C₂O₄^2-, M¹ = Urea). The characteristic features of the packing of the uranium-containing complexes are discussed in terms of molecular Voronoi–Dirichlet polyhedra. The effect of the Urea: U ratio on the structure of uranium-containing structural units is considered.     

Synthetic and structural studies of the trans bis(2-N-H-pyrrolylcarbaldimine) complexes of nickel(II) and palladium(II)

The molecular bis(2-N-H-pyrrolylcarbaldimine)nickel(II) and palladium(II) complexes are isolated in moderate yield (30–35%) from in situ assembly of the Schiff base with metal(II) salt, base, and pyrrole-2-carbaldehyde in aqueous ammonia solution. The nickel(II) complex, 1, is monoclinic, space group P2₁/c, with a=11.289(6) ?, b=5.611(3) ?, c=8.287(5) ?, β=111.620(6)°, and V=488.0(5) ?³ with Z=2, for d _calc=1.667 Mg/m³. The palladium analog, 2, is isomorphous, space group P2₁/c, with a=11.481(3) ?, b=5.5738(10) ?, c=8.276(2) ?, β=110.923(12)°, and V=494.7(2) ?³ with Z=2, for d _calc=1.965 Mg/m³. In both crystal structures, the metal resides on an inversion center. In the IR spectra, ν(C=N) appears at 1561 cm⁻¹ in 1, and 1557 cm⁻¹ in 2, while ν(N–H) shows at 3345 cm⁻¹ and 3335 cm⁻¹, respectively. The ¹H-nmr spectra reveal the C–H and N–H protons of the imine group as sharp and broad doublets, respectively, at 7.62 and 8.38 δ in 1 and at 7.92 and 9.73 δ in 2.     

On Some Transition Metal Complexes Having Orientational Properties(II). Copper(II) complexes

Alignment layers containing copper(II) complexes with acrylic acid or polyvinylpyrrolidone show homeotropic orientational properties. This behaviour is supposed to be due to the particular structure of the complex copper(II) ions. We give spectroscopic arguments to support the anchoring of liquid crystal (LC) molecules by coordination to the copper ion within the alignment layer.     

Preparation of nickel oxide– and nickel–silica nanocomposites by spray pyrolysis

Nickel oxide–silica and nickel–silica nanocomposites were prepared by spray pyrolysis of aqueous sols of silica nanoparticles containing nickel nitrate hexahydrate, without and with ethanol, respectively. During pyrolysis, the silica nanoparticles were restructured, losing their identities, while the nickel oxide or nickel particles in the composites grew by coalescence and sintering. Compactness of the composites, higher in nickel–silica composites than their counterpart nickel oxide, increased with the temperature of preparation and the concentration of nickel nitrate. Nickel always formed larger crystallites than its counterpart nickel oxide, due to its higher sintering rate. At 500 °C, the crystallite growths of nickel oxide and nickel were inhibited by the low sintering rate and the formation of nickel intermediates, respectively, while at 1000 °C their phase-pure crystallites continuously grew with the increase in the nitrate concentration.     

Electronic state of sulfide-based lithium ion conducting glasses

Electronic states of the sulfide-based lithium ion conducting glasses were calculated by the DV-Xα cluster method. The cluster models were constructed by the coordination number reported by experimental methods and the bond length estimated from the ionic radii of each ion. The movement of the Li ion was simulated by several model clusters with different positions of the moving ion. The relationship between ionic conductivity and the differential total bond overlap population (DBOP) was discussed for the sulfide-based glasses in the systems Li₂S–SiS₂–Al₂S₃ and Li₂S–SiS₂–P₂S₅. In these glasses, the DBOP with the movement of the lithium ion had good negative correlations with the ionic conductivities and positive correlations with the activation energies obtained by the experimental measurements. In any cases, the smaller change of the total bond overlap population of the moving cations played an important role for the fast ion movement in the superionic conducting glasses. This bonding state of the moving cations is one of the characteristics of the electronic state in the sulfide-based lithium ion conducting glasses.     

Colour bands of oxidized nickel dioximes

Strong colour bands are observed in the mull absorption spectra of the oxidized nickel chain dioximes bis (1,2-benzoquinonedioximato) Ni.I_0.5 and bis (diphenylglyoximato) Ni^IIIBr in the long wavelength region of the optical spectrum which are ascribed to the reduced metal-metal distance due to oxidation. The uv-visible spectra of bis (dimethylglyoximato) Ni^II and bis (diphenylglyoximato) Ni^II have also been studied in the present comparative study. All the bands in the uv-visible range are assigned. The transitions and the effects of partial oxidation on the electronic transitions are discussed.     

Eutectic crystallization of aluminium nickel alloys

The directional crystallization of eutectic Al Ni alloys was studied. Variations of the growth rate caused significant change of the microstructure and mechanical behaviour of eutectic alloys. On the base of a Tiller's analysis involving the voluminal ratio of the two phases the interphase boundary energy σ_αβ is obtained.