Diorganotin dications stabilized by neutral ligands in the solid state: [R2Sn(H2O)2(OPPh3)2](O3SCF3)2 (R = Me, Bu)

The synthesis of [R₂Sn(H₂O)₂(OPPh₃)₂](O₃SCF₃)₂ (R = Me (1), Bu (<b>2</b>)) by the consecutive reaction of R₂SnO (R = Me, Bu) with triflic acid and Ph₃PO is described. Compounds <b>1</b> and <b>2</b> feature dialkyltin(IV) dications [R₂Sn(H₂O)₂(OPPh₃)₂]^₂+ apparently stabilized by the neutral ligands in the solid state. Compounds <b>1</b> and <b>2</b> readily dehydrate upon heating at 105 and 86 &deg;C, respectively. The preparative dehydration of <b>1</b> afforded [Me₂Sn(OPPh₃)₂(O₃SCF₃)](O₃SCF₃) (<b>1a</b>), which features both bidentate and non-coordinating triflate anions. In compounds <b>1</b> and <b>2</b> the ligands Ph₃PO and H₂O are kinetically labile in solution and undergo reversible ligand exchange reactions. Compounds <b>1, 1a </b>and <b>2</b> were characterized by multinuclear solution and solid-state NMR spectroscopy, IR spectroscopy, electrospray mass spectrometry, conductivity measurements, thermogravimetry and X-ray crystallography.<br /><br /><br />

Oligomethylene-bridged dinuclear triorganotin triflates and diphenylphosphinates. Ion pairing in the solid state and electrolytic dissociation in solution of [Ph2Sn(CH2)nSnPh2X](O3SCF3) (X = OH, O2PPh2; n = 1-3)

The condensation of [Ph₂(OH)Sn(CH₂)<i>_n</i>Sn(OH)Ph₂] (<b>1-3</b>; <i>n</i> = 1-3) with HO₃SCF₃ and HO₂PPh₂ provided [Ph₂Sn(CH₂)_<i>n</i>SnPh₂(OH)](O₃SCF₃) (<b>4-6</b>; <i>n</i> = 1-3) and [Ph₂(O₂PPh₂)Sn(CH₂)_<i>n</i>Sn(O₂PPh₂)Ph₂] (<b>10-12</b>; <i>n</i> = 1-3), respectively. The reaction of [Ph₂Sn(CH₂)_<i>n</i>SnPh₂(OH)](O₃SCF₃) (<b>4-6</b>; <i>n</i> = 1-3) with HO₂PPh₂ and NaO₂PPh₂ gave rise to the formation of [Ph₂Sn(CH₂)_<i>n</i>SnPh₂(O₂PPh₂)](O₃SCF₃) (<b>7-9</b>; <i>n</i> = 1-3) and [Ph₂(OH)Sn(CH₂)_<i>n</i>Sn(O₂PPh₂)Ph₂] (<b>13-15</b>; _<i>n</i> = 1-3), respectively. In the solid state, compounds <b>4-9</b> comprise ion pairs of cationic cyclo-[Ph₂SnCH₂SnPh₂(OH)]₂²⁺, cyclo-[Ph₂Sn(CH₂)<i>_n</i>SnPh₂(OH)]⁺ (<i>n</i> = 2, 3), and cyclo-[Ph₂Sn(CH₂)_<i>n</i>SnPh₂(O₂PPh₂)]⁺ (<i>n</i> = 1-3) and triflate anions. In MeCN, the eight-membered-ring system cyclo-[Ph₂SnCH₂SnPh₂(OH)]₂²⁺ appears to be in equilibrium with the four-membered-ring system cyclo-[Ph₂SnCH₂SnPh₂(OH)]⁺. In contrast, compounds <b>10-15</b> show no ionic character. Compounds <b>1-15</b> were characterized by multinuclear NMR spectroscopy in solution and in the solid state, IR spectroscopy, conductivity measurements, electrospray mass spectrometry, osmometric molecular weight determinations, and X-ray crystallography (<b>4, 5, 7,</b> and <b>12</b>). <br /><br />

Prevalence of the thioamide {···H-N-C=S}2 synthon-solid-state (X-ray crystallography), solution (NMR) and gas-phase (theoretical) structures of O-methyl-N-aryl-thiocarbamides

Structural investigations, <i>i.e.</i> solid-state (X-ray), solution (¹H NMR) and gas-phase (theoretical), on molecules with the general formula MeOC(S)N(H)C₆H₄-4-Y: Y = H (<b>1</b>), NO₂ (<b>2</b>), C(O)Me (<b>3</b>), Cl (<b>4</b>) have shown a general preference for the adoption of an <i>E</i>-conformation about the central C&ndash;N bond. Such a conformation allows for the formation of a dimeric hydrogen-bonded {H&ndash;N&ndash;C=S}₂ synthon as the building block. In the cases of<b> 1&ndash;3</b>, additional C&ndash;H^...O interactions give rise to the formation of tapes of varying topology. A theoretical analysis shows that the preference for the <i>E</i>-conformation is about the same as the crystal packing stabilisation energy and consistent with this, the compound with Y = C(O)OMe, (<b>5</b>), adopts a Z-conformation in the solid-state that facilitates the formation of N&ndash;H^...O, C&ndash;H^...O and C&ndash;H^...S interactions, leading to a layer structure. Global crystal packing considerations are shown to be imperative in dictating the conformational form of molecules <b>1&ndash;5</b>.<br />

Optical and photocatalytic properties of nanocrystalline TiO2 synthesised by solid-state chemical reaction

Nanoparticulate TiO₂is of interest for a variety of technological applications, including optically transparent UV-filters and photocatalysts for the destruction of chemical waste. The successful use of nanoparticulate TiO₂in such applications requires an understanding of how the synthesis conditions effect the optical and photocatalytic properties. In this study, we have investigated the effect of heat treatment temperature on the properties of nanoparticulate TiO₂powders that were synthesised by solid-state chemical reaction of anhydrous TiOSO₄ with Na₂CO₃. It was found that the photocatalytic activity increased with the heat treatment temperature up to a maximum at 600 &deg;C and thereafter declined. In contrast, the optical transparency decreased monotonically with the heat treatment temperature. These results indicate that solid-state chemical reaction can be used to prepare powders of nanoparticulate TiO₂ with properties that are optimised for use as either optically transparent UV-filters or photocatalysts.<br />

Solid state recycling of 5083 Al alloy by hot extrusion

The machined chips of 5083 Al alloy were recycled by hot extrusion at 723 K with an extrusion ratio of 44:1 in air. Corrosion and mechanical properties of the recycled specimens have been compared with those of a virgin extrusion which was processed from the ingot block. As a result of salt immersion tests, mass loss of the recycled specimen was not less than twice of that of the virgin extrusion. The deterioration in corrosion properties for the recycled specimen was attributed to the excessive contamination of Fe which promoted galvanic corrosion. As a result of tensile tests, the recycled specimen exhibited a good combination of high strength and high elongation to failure at room temperature. The excellent mechanical properties for the recycled specimen were attributed to the refined microstructure. However, the elongation to failure of the recycled specimen at elevated temperatures more than 573 K was lower than that of the virgin extrusion. The contamination of oxide particles is likely to be responsible for the lower elongation in the solid recycled specimen. <br />

Cation dynamics in dimethyl-pyrrolidinium-based solid-state ion conductors

Dimethyl-pyrrolidinum-based salts have been investigated by means of DSC, conductivity, NMR and Raman spectroscopy. The investigation aims to study the effect of the anion on the behaviour of the salt, in terms of plastic properties as well as rotational degrees of freedom of the cation. The materials range from the non-plastic iodide salt to the highly plastic BF₄ salt, which flows under its own weight at elevated temperatures. The different rotational and translational motions of the cations, and the difference between rotator and plastic phases are discussed.<br />

High mobility I− / I3− redox couple in a molecular plastic crystal: A potential new generation of electrolyte for solid-state photoelectrochemical cells

A series of new electrolyte materials based on a molecular plastic crystal doped by different iodide salts together with iodine have been prepared and characterized by thermal analysis, ionic conductivity, electrochemical and solid-state NMR diffusion measurements. In these materials, the plastic crystal phase of succinonitrile acts as a good matrix for the quaternary ammonium based iodides and iodine and appears to act in some cases as a solid-state &ldquo;solvent&rdquo; for the binary dopants. The materials were prepared by mixing the components in the molten state with subsequent cooling into the plastic crystalline state. This resulted in waxy-solid electrolytes in the temperature range from &minus; 40 to 60 &deg;C. The combination of structural variation of the cations, and fast redox couple diffusion (comparable with liquid-based electrolytes), as well as a high ionic conductivity of up to 3 &times; 10^{&minus; 3} S cm^{&minus; 1} at ambient temperature, make these materials very attractive for potential use in solid-state photoelectrochemical cells.<br />

Rapid I−/I3− diffusion in a molecular-plastic-crystal electrolyte for potential application in solid-state photoelectrochemical cells

High current-carrying capacity and rapid, liquidlike diffusion were achieved in a dye-sensitized solar cell (DSSC) based on the plastic-crystalline electrolyte succinonitrile and the I^&minus;/I₃^&minus; redox couple (see diagram). This could lead to the development of true solid-state DSSCs without conventional organic-liquid electrolytes, which can cause problems with long-term device stability.<br />

Solid state ion transport and phase behaviour in composites of N,N-methyl propylpyrrolidinium tetrafluoroborate and amorphous polyethylene oxide

The binary and ternary addition of 2 wt.% LiBF₄ and 2 wt.% amorphous polyethylene oxide (aPEO) respectively to the plastic crystal forming salt P₁₃BF₄ (where P₁₃⁺=methylpropyl pyrrolidinium cation) was investigated with specific focus on the phase behaviour and evaluation of transport characteristics. Differential scanning calorimetry (DSC), optical thermomicroscopy, solid state nuclear magnetic resonance (NMR), and AC impedance spectroscopy were used to develop an understanding of the conduction process in the pure and mixed systems. The morphology of the ternary compound appeared as hexagonal spherulites upon solidification. Multinuclear NMR Pulsed Field Gradient measurements (¹H,¹⁹F,⁷Li) to probe both cation and anion diffusion coefficients are reported. The anion is shown to be the most diffusive (at 320 K:¹⁹F=2.5&times;10^&minus;11 m² s^&minus;1; 1H: 1.8&times;10^&minus;11 m² s^&minus;1; ⁷Li: 1.1&times;10^&minus;11 m² s^&minus;1) in the ternary compound, with enhanced conductivity (2.7&times;10^&minus;5 S cm^&minus;1 at 310 K) just below the melt.<br />

Solid state NMR characterization of polyrrole : the nature of the dopant in PF6− doped films

³¹P and ¹⁹F solid state NMR have been used to study the nature of the PF₆&minus; anion in polypyrrole films at various levels of oxidation. It appears that the symmetric PF₆&minus; unit remains undistorted and unchanged throughout, suggesting that it is predominantly acting only as a counterion and not as a true &lsquo;dopant&rsquo;, since any distortion in the phosphorous environments would result at the very least in chemical shift anisotropy of the ³¹P nucleus. A second set of phosphorous and fluorine resonances, which are consistent with a difluoride phosphorous compound, appeared in the films. Upon electrochemical reduction of the polymer, the undistorted PF₆&minus; anion leaves the film whereas the second phosphorous species remains. Re-oxidation of the polymer reverses the processes observed during reduction.<br />