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In hydrothermal synthesis of LiFePO4 a slower addition of Li+ to a mixture of Fe2+ + PO43- increased Fe2+ oxidation, defects within the LiFePO4 structure and iron impurities in the product. No link was seen between Li3PO4 formation and addition rate.

Equilibrium phases of the Bi2O3-WO3 system, synthesized using the citrate-gel method with slow cooling, have been systematically investigated for samples with 22–27 mol% WO3. Annealing temperature and content of WO3 were shown to play a significant role in the phases present. Both powder X-ray diffraction and Raman spectroscopy revealed that the room temperature equilibrium phases were 7Bi2O3-WO3 and 7Bi2O3-2WO3, with the latter being dominant. Variable temperature Raman spectroscopy showed that both these phases were present up to 850 °C, with the possible formation of a third unidentified phase at higher temperatures. The ionic conductivities of the mixed-phase materials were between that for the pure 7Bi2O3-WO3 and 7Bi2O3-2WO3 phases and at 700 °C was only about three times lower than that of the pure defect fluorite phase of the 22 mol% WO3 samples. The Arrhenius plots showed no sudden increase in conductivity between 300 and 750 °C providing evidence that no major phase change occurred in this temperature range.

A major noble way to realizing high-efficiency organic solar cell device is the use of ternary blends with non-fullerene acceptors. Although offset in the band gap (E-gap) of the donor/acceptor material is negligible, it still exhibits ultra-fast and efficient charge separation. Regardless of the progress made, device optimization and fundamental understanding of the role of structural configurations in charge transport mechanisms is still on the way. The performances and stability of such devices largely depend on the nanoscale solid-state interpenetrating morphology of their donor/acceptor components within the photoactive region. Here, we analyze the effects of the second acceptor material PC71BM which is fullerene derivative on the nano-morphology within the bulk-heterojunction active layer made of PBDB-T (as donor) and non-fullerene derivative ITIC-Th (as acceptor) as well as the photovoltaic performance. Upon varying the blend ratio, 2:1:1 ratio showed a remarkable performance with more photo-generated current resulting from the favorable nano-scaled interpenetrating network with less traps as can be visualized in Fig. 1.

Eu-doped ZnO (ZnO:Eu3+) thin films deposited by RF magnetron sputtering have been investigated to establish the effect of annealing on the red photoluminescence. PL spectra analysis reveal a correlation between the characteristics of the red photoluminescence and the annealing temperature, suggesting efficient energy transfer from the ZnO host to the Eu3+ ions as enhanced by the intrinsic defects levels. Five peaks corresponding to 5D0–7FJ transitions were observed and attributed to Eu3+ occupancy in the lattice sites of ZnO thin films. As a proof of concept a dye sensitized solar cell with ZnO:Eu3+ thin films of high optical transparency was fabricated and tested yielding a PCE of 1.33% compared to 1.19% obtained from dye sensitized solar cells (DSSC) with pristine ZnO without Eu produced indicating 11.1% efficiency enhancement which could be attributed to spectral conversion by the ZnO:Eu3+.

A series of spinel-type MnxNi1-xCo2O4 (x = 0, 0.3, 0.5, 0.7, 1) oxides were synthesized by using a citrate sol-gel technique. The structural, magnetic and electronic properties of the oxides with different Mn content were investigated using X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). The XRD and FTIR studies revealed that MnxNi1-xCo2O4 formed in a cubic structure for all the compositions synthesized. Transmission electron microscopy (TEM) studies show cubic nano-plates for x = 0 and on increasing Mn concentration, agglomerated nanoparticles with sphere-like shape are observed with a particle size in the range of 11.7 nm–22.1 nm. This is in close agreement with the results of XRD analysis. The Mn 2p, Ni 2p, and Co 2p XPS spectra reveal the coexistence of Mn2+, Mn3+, Ni2+, Ni3+, Co2+, and Co3+ species on the surface of MnxNi1-xCo2O4 samples in differing proportions. The measurements of magnetic properties at room temperature show that the samples have some ferromagnetic behaviour. The saturation magnetization, remnant magnetization, and coercivity of the nanoparticles vary significantly with a concentration of Mn, which tends to be distributed in both tetrahedral and octahedral positions of the spinel lattice.

One of the pathways responsible for the deactivation of Fischer-Tropsch catalysts is the loss of active metal surface area due to nanoparticle agglomeration. To combat this effect efforts have been made to increase the interaction between the metal nanoparticles and the support using materials like silica. In this study, the supported metal particles were covered with a highly porous layer of silica to stabilize the Co nanoparticles on a titania support both during reduction and under reaction conditions. Co3O4 nanoparticles (size range: 8–12 nm) supported on titania were stabilized by coating them with a thin layer of mesoporous silica ( ∼ 4 nm) to make Fischer-Tropsch catalysts that are less prone to sintering (Co/TiO2@mSiO2). To mitigate the strong metal support interactions brought about by the titania and silica a Ru promoter was loaded together with the cobalt nanoparticles onto the titania (CoRu/TiO2@mSiO2). Temperature programmed XRD studies on the evolution of the Co metal nanoparticles showed that there was no significant particle size growth under reduction conditions in the temperature range from 30 to 600 °C. Chemisorption studies following reduction under hydrogen at 350 °C and 450 °C gave results consistent with the in situ XRD data when compared to the Co/TiO2. Fischer-Tropsch synthesis on the Co/TiO2@mSiO2 and CoRu/TiO2@mSiO2 catalysts encapsulated inside the mesoporous silica shell exhibited good catalytic performance without any display of significant mass transport limitations that might arise due to a silica shell coating of the active sites. For these two catalysts the Fischer-Tropsch activity increased with reduction temperature without any significant negative changes in their selectivity due to sintering, while the activity on Co/TiO2 decreased due to Co nanoparticle sintering.

Down conversion has been applied to minimize thermalization losses in photovoltaic devices. In this study, terbium-doped ZnO (ZnO:Tb3+) thin films were deposited on ITO-coated glass, quartz and silicon substrates using the RF magnetron sputtering technique fitted with a high-purity (99.99%) Tb3+-doped ZnO target (97% ZnO, 3% Tb) for use in organic solar cells as a bi-functional layer. A systematic study of the film crystallization dynamics was carried out through elevated temperature annealing in Ar ambient. The films were characterized using grazing incidence (XRD), Rutherford backscattering spectrometry (RBS), atomic force microscopy, and UV-visible transmittance and photoluminescence measurements at an excitation wavelength of 244 nm. The tunability of size and bandgap of ZnO:Tb3+ nanocrystals with annealing exhibited quantum confinement effects, which enabled the control of emission characteristics in ZnO:Tb3+. Energy transfer of ZnO → Tb3+ (5D3–7F5) was also observed from the photoluminescence (PL) spectra. At an inter-band resonance excitation of around 300–400 nm, a typical emission band from Tb3+ was obtained. The ZnO:Tb3+ materials grown on ITO-coated glass were then used as bi-functional layers in an organic solar cell based on P3HT:PCBM blend, serving as active layers in an inverted device structure. Energy transfer through down conversion between ZnO and Tb3+ led to enhanced absorption in P3HT:PCBM in the 300–400 nm range and subsequently augmented Jsc of a Tb3+-based device by 17%.

Mn substituted MnxZn1−xCo2O4 (x = 0, 0.3, 0.5, 0.7, 1) oxides were synthesized by a facile co-precipitation method followed by calcination at 600 °C. The presence of manganese ions causes appreciable changes in the structural and magnetic properties of the Mn-substituted ZnCo2O4. The morphologies, structures, and electronic properties of Mn–Zn–Co oxide microspheres were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The X-ray diffraction and Fourier transform infrared spectroscopy results confirmed the formation of spinel MnxZn1−xCo2O4. It was shown that the Mn–Zn–Co oxide microspheres increase in size and become regular in shape with increasing Mn concentration with the crystal size lying in the range from 19.1 nm to 51.3 nm. Magnetization measurements were carried out using a vibrating sample magnetometer at room temperature and 10 K. The saturation magnetization is observed to increase with increasing Mn concentration from x = 0 to x = 1.

Pyrochlore and defect fluorite structured materials with A23+B24+O7 stoichiometry have a wide variety of potential commercial applications, from solid oxide fuel cell electrolytes to thermal barriers and radioactive nuclei immobilisation matrixes. Previous reported synthetic methodologies for the preparation of these materials that are based on Pb(IV) use high pressures and temperatures which are not repeatable with the infrastructure available within typical laboratories. Additionally, commonly used sol gel techniques are ineffective in producing the desired materials due to the oxidative power of lead(IV) compounds. Developing a milder synthetic approach (which can lend itself to bulk production) to obtain these compounds is therefore important if they are to achieve any commercial importance due to inherent properties. Herein we describe a mild synthetic approach whereby existing and new lead(IV) based defect fluorite structured materials have been prepared. Evidence for their structure, nano-...

Eu-doped ZnO (ZnO:Eu3+) thin films deposited by RF magnetron sputtering have been investigated to establish the effect of annealing on the red photoluminescence. PL spectra analysis reveal a correlation between the characteristics of the red photoluminescence and the annealing temperature, suggesting efficient energy transfer from the ZnO host to the Eu3+ ions as enhanced by the intrinsic defects levels. Five peaks corresponding to 5D0–7FJ transitions were observed and attributed to Eu3+ occupancy in the lattice sites of ZnO thin films. As a proof of concept a dye sensitized solar cell with ZnO:Eu3+ thin films of high optical transparency was fabricated and tested yielding a PCE of 1.33% compared to 1.19% obtained from dye sensitized solar cells (DSSC) with pristine ZnO without Eu produced indicating 11.1% efficiency enhancement which could be attributed to spectral conversion by the ZnO:Eu3+.

We report an investigation on the effect of oxygen flow rate on the structural and optical properties of zinc oxide thin films prepared by RF magnetron sputtering. The structural measurements were carried using grazing incidence X-ray diffraction, atomic force microscopy and Raman spectroscopy. The role of oxygen partial pressure on the crystallinity, the surface morphology and vibrational modes has been established. The optical properties of the films were investigated using FR-Basic-VIS/NIR fitted with FR-Monitor software for film thickness, refractive index and color determination. The film thickness is observed to increase when oxygen is introduced at 4 sccm but eventual decrease with increase in the flow rate an indication of initial increase in rate of deposition followed by reduction. Elaborate explanations of these trends are provided.

The thermal production of 4PbO·PbSO4 was comprehensively studied and characterized for two syntheses routes, i.e. either heating 3PbO·PbSO4·H2O, or a mixture of 4PbO:PbSO4, in air to about 700 °C. In the 3PbO·PbSO4·H2O approach, the formation of an intermediate amorphous phase occurred at around 210 °C with the loss of H2O from the hydrated structure. Formation of 4PbO·PbSO4 initiated at around 270 °C with predominantly 4PbO·PbSO4 and 13% residual PbO·PbSO4 existing at 700 °C. With the synthesis route of mixing a stoichiometric ratio of 4PbO with PbSO4, an intermediate phase of PbO·PbSO4 formed at around 300 °C, before the 4PbO·PbSO4 phase started to form at around 500 °C. Upon further heating, 4PbO·PbSO4 was the predominant phase with 8% of PbO·PbSO4 remaining. Both samples decomposed upon further heating to 850 °C. Powder neutron diffraction studies of the final 4PbO·PbSO4 products from the two different synthesis routes showed similar crystallographic unit cell lattice parameters with slight differences in the PbO:PbSO4 contents. This could possibly be linked to differences observed in the microscopic crystallite shapes from the two synthesis routes.

Mesoporous hollow carbon spheres (MHCSs) were synthesized (d = 290 nm; carbon shell 20–35 nm), and their hollow morphology was exploited to study the influence of Ru nanoparticle location relative to Co3O4 nanoparticles on the reduction behavior and activity of Co Fischer–Tropsch catalysts. Ru nanoparticles were loaded both inside and outside the MHCS, while Co3O4 particles (ca. Co 15 wt % loading) were loaded on the outside of the MHCS. The use of in situ powder X-ray diffraction (PXRD) and temperature-programmed reduction studies on the catalysts indicated the effect of Ru location on the Co3O4 reduction pathways. A secondary hydrogen spillover effect was invoked to explain a complete reduction of the Co3O4 on Ru@MHCS@Co at 450 °C. Secondary hydrogen spillover enhanced the CoO to Co transformation by lowering the reduction temperature when compared to the unpromoted catalyst. Primary hydrogen spillover was inferred to explain the complete reduction of Co3O4 to Co metal on CoRu/MHCS at 300 °C. After catalyst activation at 350 °C, the primary spillover process yielded a catalyst with higher Fischer–Tropsch activity (ca. 2×) than the unpromoted catalyst and the catalysts where Ru and Co were separated by the mesoporous carbon shell. This was partially related to the Co phases that formed on the carbon support during reduction and the catalyst degree of reduction that was reliant on the type of hydrogen spillover process.

We evaluated the chemical sequestration of carbon dioxide into the phosphogypsum from the Lowveld region of South Africa. The phosphogypsum was converted to saleable ammonium sulphate and precipitated calcium carbonate in a modified Merseburg process. The heat from the ammonium carbonate formation exothermicity increased the temperature in the gypsum conversion reactor contents by 35 K, significantly reducing the heating requirements to achieve the reaction temperature of 343 K. The modified process will lower capital layout but no fundamental energy superiority or inferiority to the original Merseburg process. The gypsum conversion efficiency of 95 % was achieved. The purity of the ammonium sulphate produced is comparable to the chemical grade, commercially available in South Africa. The calcium carbonate precipitated as calcitic scalenohedral polymorphs with a mean size of 3.4 μm in diameter. The economic feasibility study must be done to determine the cost implication of the omission of the carbon dioxide scrubbing towers in the modified Merseburg process.

Mn substituted Mn

Down conversion has been applied to minimize thermalization losses in photovoltaic devices. In this study, terbium-doped ZnO (ZnO:Tb

In the gold mining Witwatersrand Basin of South Africa, efflorescent mineral crusts are a common occurrence on and nearby tailings dumps during the dry season. The crusts are readily soluble and generate acidic, metal- and sulphate-rich solutions on dissolution. In this study, the metal content of efflorescent crusts at an abandoned gold mine tailings dump was used to characterise surface and groundwater discharges from the site. Geochemical modelling of the pH of the solution resulting from the dissolution of the crusts was used to better understand the crusts' potential impact on water chemistry. The study involved two approaches: (i) conducting leaching experiments on oxidised and unoxidised tailings using artificial rainwater and dilute sulphuric acid and correlating the composition of crusts to these leachates and (ii) modelling the dissolution of the crusts in order to gain insight into their mineralogy and their potential impact on receiving waters. The findings suggested that there were two chemically distinct discharges from the site, namely an aluminium- and magnesium-rich surface water plume and an iron-rich groundwater plume. The first plume was observed to originate from the oxidised tailings following leaching with rainwater while the second plume originated from the underlying unoxidised tailings with leaching by sulphuric acid. Both groups of minerals forming from the respective plumes were found to significantly lower the pH of the receiving water with simulations of their dissolution found to be within 0.2 pH units of experimental values. It was observed that metals in a low abundance within the crust (for example, iron) had a stronger influence on the pH of the resulting solutions than metals in a greater abundance (aluminium or magnesium). Techniques such as powder X-ray diffraction (PXRD) and in situ mineral determination techniques such as remote sensing can effectively determine the dominant mineralogy. However, the minerals or metals incorporated through solid solution into bulk mineralogy that dominates the chemistry of the solutions upon their dissolution may occur in minor quantities that can only be predicted using chemical analysis. Their mineralogy can be predicted using geochemical modelling and can provide a set of hypothetical minerals that upon dissolution yield a solution similar to that of the actual crusts. This realisation has a bearing on decision-making such as in risk assessment and designing pollutant mitigation strategies.

Carbon spheres (CSs) synthesised by the hydrothermal approach were explored as a model support material for a bimetallic Fe–Co Fischer–Tropsch (FT) catalyst. The CSs were characterised by N2 adsorption–desorption, thermogravimetric analysis, FTIR spectroscopy and powder XRD. If annealed at 900 °C for 4 h, the CSs exhibited an improved surface area, thermal stability and crystallinity. A series of Fe–Co bimetallic FT catalysts supported on the annealed CSs were prepared by co‐precipitation. A variety of Fe‐to‐Co ratios were used with the total metal loadings maintained at 10 %. Catalyst reducibility studies were performed by H2 temperature‐programmed reduction and in situ powder XRD. Catalysts with a Fe/Co ratio of 5:5 (w/w) showed Co–Fe alloy formation upon reduction at >450 °C. Interestingly, the presence of this alloy did not correlate with high C5+ selectivities during FT synthesis; rather the Co‐rich/Fe‐poor catalyst gave the best selectivity. The CSs allowed the metal–metal interactions in the bimetallic systems to be monitored because of the weak interaction of the metals with the support. ePDFPDF PDF Tools Share Abstract Carbon spheres (CSs) synthesised by the hydrothermal approach were explored as a model support material for a bimetallic Fe–Co Fischer–Tropsch (FT) catalyst. The CSs were characterised by N2 adsorption–desorption, thermogravimetric analysis, FTIR spectroscopy and powder XRD. If annealed at 900 °C for 4 h, the CSs exhibited an improved surface area, thermal stability and crystallinity. A series of Fe–Co bimetallic FT catalysts supported on the annealed CSs were prepared by co‐precipitation. A variety of Fe‐to‐Co ratios were used with the total metal loadings maintained at 10 %. Catalyst reducibility studies were performed by H2 temperature‐programmed reduction and in situ powder XRD. Catalysts with a Fe/Co ratio of 5:5 (w/w) showed Co–Fe alloy formation upon reduction at >450 °C. Interestingly, the presence of this alloy did not correlate with high C5+ selectivities during FT synthesis; rather the Co‐rich/Fe‐poor catalyst gave the best selectivity. The CSs allowed the metal–metal interactions in the bimetallic systems to be monitored because of the weak interaction of the metals with the support.

The phase behaviour of Fe and Co particles, supported on CaCO3 was studied using mainly in situ PXRD and Mossbauer spectroscopy. This is of interest as these systems can be used as catalysts to produce multi-walled carbon nanotubes (MWCNTs) following appropriate heat treatment and reduction. The Fe–Co/CaCO3 samples were prepared by deposition of the metallic particles from solution onto the support. The study indicated that the CaCO3 support reacted in air or N2 with the iron and cobalt present in all three samples studied (10% Fe/CaCO3, 10% Co/CaCO3 and 10% Fe–Co/CaCO3) to give a brownmillerite structure with the general formula Ca2M2O5 (M = Fe, Co or Fe + Co). Reduction of the bimetallic catalyst gave Fe2Co alloy and Co. This confirms earlier reports by other authors that implicated this alloy as the active phase in the synthesis of the MWCNTs. The bimetallic catalyst was easier to reduce than the mono-metallic catalysts.

The vibrational mode for the cubic symmetry of boron nitride (BN) has been produced by boron ion implantation of hexagonal boron nitride (h-BN). The optimum fluence at 150 keV was found to be 5 × 1014 ions/cm2. The presence of the c-BN phase was inferred using glancing incidence XRD (GIXRD) and Fourier Transform Infrared Spectroscopy (FTIR). After implantation, Fourier Transform Infrared Spectroscopy indicated a peak at 1092 cm−1 which corresponds to the vibrational mode for nanocrystalline BN (nc-BN). The glancing angle XRD pattern after implantation exhibited c-BN diffraction peaks relative to the implantation depth of 0.4 μm.

C.G. and J.A.S. would like to thank the UK EPSRC for funding their Ph.D. studentships via the Centre for Doctoral Training in “New and Sustainable Photovoltaics” (EP/L01551X/1). The authors also thank the UK STFC and EPSRC for part‐funding this work via grants ST/R002754/1 “Synchrotron Techniques for African Research and Technology” and “Hybrid Polaritonics” (EP/M025330/1). A.S. hereby acknowledges the financial assistance of the South Africa National Research Foundation (NRF), University of the Witwatersrand – Material and Energy Research Group (MERG) and DST‐NRF Centre of Excellence in Strong Materials (CoE‐SM) toward this research. Mixed cation perovskites currently achieve very promising efficiency and operational stability when used as the active semiconductor in thin‐film photovoltaic devices. However, an in‐depth understanding of the structural and photophysical properties that drive this enhanced performance is still lacking. Here the prototypical mixed‐cation mixed‐halide perovskite (FAPbI3)0.85(MAPbBr3)0.15 is explored, and temperature‐dependent X‐ray diffraction measurements that are correlated with steady state and time‐resolved photoluminescence data are presented. The measurements indicate that this material adopts a pseudocubic perovskite α phase at room temperature, with a transition to a pseudotetragonal β phase occurring at ≈260 K. It is found that the temperature dependence of the radiative recombination rates correlates with temperature‐dependent changes in the structural configuration, and observed phase transitions also mark changes in the gradient of the optical bandgap. The work illustrates that temperature‐dependent changes in the perovskite crystal structure alter the charge carrier recombination processes and photoluminescence properties within such hybrid organic–inorganic materials. The findings have significant implications for photovoltaic performance at different operating temperatures, as well as providing new insight on the effect of alloying cations and halides on the phase behavior of hybrid perovskite materials. Postprint

The synthesis and thermoresponsive behaviour of high purity CuTi2(PO4)3 (CTP) was examined while heating in air and nitrogen at atmospheric pressure. It is known that a spontaneous redox reaction involving the Cu+ cations that are contained in the Ti2(PO4)3− crystal structure converts the CTP phase to the related Cu0.5Ti2(PO4)3 (CTP2) phase when heated in air. However, the extent of this reaction and the effect that it has on the CTP crystal structure has not been established. Using in situ powder X-ray diffraction it was found that during heating in air, the migration of Cu+ cations out of the Ti2(PO4)3− crystal lattice results in the growth of a CuO phase. To quantify the extent of the migration of the Cu+ cations out of the Ti2(PO4)3− crystal lattice, quantitative phase analysis was used to show that the redox reaction converts the CTP phase to the CTP2 phase in the temperature region from 450 to 530 °C. When increasing the temperature above 530 °C it was found that the CTP phase was spontaneously regenerated forming a high temperature form of the parent CTP phase. Previously heat-treated CTP samples were subjected to further heat treatments and produced different quantitative phase behaviour when compared to a fresh CTP sample. Most significantly it was found that the CTP2 phase was prevalent over a broader temperature range. Comparison of the high temperature and parent CTP phases showed differences between the Cu+ site occupancies. Further heat treatment under nitrogen suppressed the redox reaction and stabilized the CTP phase. This allowed the calculation of the coefficients of thermal expansion (CTE) of CTP across a broad temperature range (30–900 °C). Analysis of the CTP lattice constants via Parametric Rietveld refinement showed that the compound exhibited moderate thermal expansion up to 900 °C.

Au nanoparticles isolated on the tips of a thermally stable, radially aligned nano-structure providing a highly sinter-resistant catalyst., When Au is subdivided to the nanoscale its reactivity changes from an inert nature to one of incredible reactivity which is not replicated by other catalysts. When dispersed onto metal oxides such as TiO2, nano-Au has shown high reactivities for a multitude of reduction and oxidation reactions of industrial importance with potential and current uses such as, CO oxidation, NOx reduction, purification of hydrogen for fuel cells, water gas shift reactions, abatement of volatile organic compounds (VOC's) as well as pollution and emission control systems such as autocatalysts. However, many industrially important reactions and applications operate under harsh conditions where the catalyst is exposed to high temperatures and further needs to operate for extended periods of time. These conditions cause Au nanoparticle sintering whereby small, highly active clusters form large clusters which are catalytically inactive. For this reason, research into stabilizing Au nanoparticles has abounded with a goal of producing durable, thermally stable catalysts for industrial applications. Here we show a durable, thermally stable Au–TiO2 catalyst which has been developed by rational design. The catalyst exhibits a 3-dimensional, radially aligned nanorod structure, already locked into the thermodynamically stable polymorph, via a scalable and facile synthesis, with Au nanoparticles isolated on the support structure. As the Au nanoparticles are highly stable the new catalyst is able to maintain light-off for CO oxidation below 115 °C even after multiple cycles at 800 °C. This ability of the catalyst to resist multiple thermal cycles to high temperature while remaining active at low temperatures shows promise for various industrial applications. The thermal stability of the catalyst is investigated and characterized through morphological and structural studies.

High pressure–temperature (P–T) phases of the ZrxHf1−xO2 (x = 0.5) solid-solution have been stabilised in a CO2 laser heated diamond anvil cell. At room-temperature the monoclinic to orthorhombic-I structural transformation is initiated at 5–8 GPa. The X-ray diffraction (XRD) studies show these two phases coexist to above ∼15 GPa. A progressive increase in the orthorhombic-I phase abundance occurs, to culminate in full conversion at ∼20 GPa. At this lower threshold of ∼20 GPa transformation to the orthorhombic-II (cotunnite) structure can be initiated by heating in the range of 600–1200 °C. Substantial conversion to the cotunnite phase occurs in the same temperature range at 25–30 GPa. Raman signatures have been assigned to the two orthorhombic high-pressure phases, aided by the qualitative assessment of the complementary XRD data. Decompression experiments show that phase mixture composites of these high pressure structures, possibly with enhanced tribological properties, can be recovered to ambient conditions.

Vanadium phosphate oxide (VPO) catalysts derived from VOHPO4·0.5H2O and VO(H2PO4)2 precursors showed improved rates in the catalysed liquid phase oxidation of p-cymene. Both catalysts showed high performance with conversions of up to 30% achieved within 3 h with a selectivity towards the tertiary cymene hydroperoxide (TCHP) of 75–80% when compared to lower conversions and poorer TCHP selectivity in the non-catalysed industrial oxidation processes that takes about 8–12 h reaction time. The temperature dependent structural changes during activation within the catalysts were studied by in situ XRD and TGA-MS. The in situ XRD showed that the VO(H2PO4)2 form mainly an amorphous phase at temperature up to 600 °C while above 650–750 °C a stable VO(PO3)2 phase was obtained. The in situ XRD studies of the (VO)2P2O7 phase derived from VOHPO4·0.5H2O showed to became more crystalline with increasing temperature from 400 to 750 °C. No formation of VOPO4 phases were observed in the activated (VO)2P2O7 catalyst even at high temperature under the in situ XRD conditions. VPO catalysts derived from VOHPO4·0.5H2O and VO(H2PO4)2 precursors improve oxidation rates and improved tert-cymene hydroperoxide selectivity during the liquid-phase oxidation of p-cymene compared to non-catalyzed oxidations.

Ten inorganic–organic hybrids have been synthesized and characterized by single crystal X-ray diffraction experiments. The inorganic component is based on lead(II) iodide units and four different types of alkylammonium cations. The structural motif adopted by the inorganic component has 2-D layers of corner-sharing PbI6 octahedra, which are closely related to the K2NiF4 and RbAlF4 structure types. This motif is observed in hybrids containing alkylammonium cations (ZCnH2nNH3) that contain three different heteroatoms: [(HOC2H4NH3)2PbI4] and [(HOC3H6NH3)2PbI4], [(BrC2H4NH3)2PbI4] and [(ICnH2nNH3)2PbI4] (n = 2–6). Additionally the hybrids [(H3NC2H4S2C2H4NH3)PbI4] and [(NH3C2H4S2C2H4NH3)2PbI5·I] crystallized from a single solution and have two distinct inorganic motifs, the former has 2-D layers of corner-sharing octahedra and the latter has 1-D chains of corner-sharing octahedra. The identity of the heteroatom and the chain length have an effect on the overall packing exhibited by the hybrid structures.

Three inorganic–organic layered perovskite-type hybrids of the general formula [(C n H2n + 1NH3)2PbI4], n = 4, 5 and 6, display a number of reversible first-order phase transitions in the temperature range from 256 to 393 K. [(C4H9NH3)2PbI4] has a single phase transition, [(C5H11NH3)2PbI4] has two phase transitions and [(C6H13NH3)2PbI4] has three phase transitions. In all three cases, the lowest-temperature phase transition is thermochromic and the crystals change colour from yellow in their lowest-temperature phase to orange in their higher-temperature phase for [(C4H9NH3)2PbI4] and [(C6H13NH3)2PbI4], and from orange to red for [(C5H11NH3)2PbI4]. The structural details associated with this phase transition have been investigated via single-crystal X-ray diffraction, SC-XRD, for all three compounds.

The crystal structures of the two organic-inorganic hybrids bis(4-aminopyridinium) hexachloridostannate(IV), (C(5)H(7)N(2))(2)[SnCl(6)], and bis(p-toluidinium) hexachloridostannate(IV), (C(7)H(10)N)(2)[SnCl(6)], differ in the way their cations pack in the layered structures. The Sn atom in the 4-aminopyridinium compound lies on an inversion centre.

The complex trans-[Rh(P(3-py)3)2(CO)Cl], 1 ,w as synthesised in our laboratories from the reaction of [Rh(CO)2Cl]2 and 4.2 equivalents of P(3-py)3 in dichloromethane at r.t.. Yellow crystals were obtained via slow diffusion of pentane into the reaction solution after removal of a part of the solvent in vacuo. The reaction with P(4-py)3, however, gave a yellow powder very insoluble in dimethyl sulfoxide (DMSO) or acetone, and we suspect the formation of oligomers by binding of the well-accessible nitrogen atoms to other rhodium centres. The chemical shift of the coordinated ligand in the 31 P NMR spectrum as well as the frequency of the CO stretching vibration are shown in Table 1n ext to those values of the previous report where 1 was obtained in absolute ethanol from [Rh(CO)2Cl]2 and P(3-py)3 [15]. The new cationic complexes trans-[Rh(P(3-pyH)3)2(CO) Cl][CF3SO3]6, 3 ,a ndtrans-[Rh(P(4-pyH)3)2(CO)Cl] [CF3SO3]6, 4, (Table 1) can be obtained via reaction of [Rh(CO)2Cl]2 with the protonated tri(3-pyridyl)phosphineligandas the tris(trifluoromethanesulfonate) salt [P(3-pyH)3]3[CF3SO3]3 or its 4-pyridyl analogue

The crystal structures of the two isomers bis(1-phenylethylammonium) hexachloridostannate(IV) and bis(2-phenylethylammonium) hexachloridostannate(IV), both (C(8)H(12)N)(2)[SnCl(6)], exhibit alternating organic and inorganic layers, which interact via N-H...Cl hydrogen bonding. The inorganic layer contains an extended two-dimensional hydrogen-bonded sheet. The Sn atom in the 1-phenylethylammonium salt lies on an inversion centre.

The three isostructural compounds butyl­ammonium hexa­chlorido­tin(IV), pentyl­ammonium hexa­chlorido­tin(IV) and hexyl­ammonium hexa­chlorido­tin(IV), (CnH2n+1NH3)2[SnCl6], with n = 4, 5 and 6, respectively, crystallize as inorganic–organic hybrids. As such, the structures consist of layers of [SnCl6]2− octa­hedra, separated by hydro­carbon layers of inter­digitated butyl­ammonium, pentyl­ammonium or hexyl­ammonium cations. Corrugated layers of cations alternate with tin(IV) chloride layers. The asymmetric unit in each compound consists of an anionic component comprising one Sn and two Cl atoms on a mirror plane, and two Cl atoms in general positions; the two cations lie on another mirror plane. Application of the mirror symmetry generates octa­hedral coordination around the Sn atom. All compounds exhibit bifurcated and simple hydrogen-bonding inter­actions between the ammonium groups and the Cl atoms, with little variation in the hydrogen-bonding geometries.

Six inorganic–organic hybrids have been synthesized and characterised by single-crystal X-ray diffraction experiments. The inorganic component is based on lead(II) iodide units and the organic component various cyclic hydrocarbons with only a primary ammonium group as a ring substituent. If the organic component is cyclopropylammonium, cyclobutylammonium, cyclopentylammonium and cyclohexylammonium, the inorganic motif observed is based on the cubic perovskite structure type and consists of 2-D layers of corner-sharing octahedra, in the ratio of 1∶2 inorganic–organic. lead(II) iodide and cycloheptylammonium combined to give 1-D chains of corner-sharing lead iodide octahedra and similarly, lead(II) iodide and cyclooctylammonium gave 1-D chains of face-sharing octahedra. A quantitative measure of the steric effects of the size of the cyclic rings on the tilting of the inorganic layers is proposed.

Distorted square pyramidal complexes of molybdenum (η 5 -C 5 H 4 Me)Mo(CO) 2 (PR 3 )I (R 3 = PhMe 2 ( 2a ); PhEt 2 ( 3a ) and Et 3 ( 4a )) have been synthesized and the structures of the lateral ( cis ) isomers have been determined by X-ray diffraction. The cone ( Θ ) and solid ( Ω ) angles as well as the angular profiles of the phosphine ligands in the complexes have been computed using the program steric . Values for the crystallographic cone and solid angles calculated for 2a , 3a and 4a are Θ (129°, 135° and 139°) and Ω (2.73, 2.99 and 2.93 sr), respectively. A search of the Cambridge Structural Database (CSD) was made for piano stool, 5- and 6-coordinate complexes containing the title phosphine ligands. Results from this study show a wide range of sizes for each of the ligands and even the seemingly simple PPhMe 2 ligand exhibited a wide range of values for the cone (113–137°) and solid (2.49–3.07 sr) angles. These observations have been rationalized and related to the possible group conformations from the crystallographic data.

In this paper we report the synthesis and the crystal structure of inorganic–organic hybrids containing various lead halides as the inorganic motif and a primary amine as the organic constituent. The organic molecule investigated is (C6H5C*H(CH3)NH2) and both the R and S as well as the racemic (±) forms were used. Within the structures obtained, three different inorganic motifs are displayed by the lead halide octahedra: 1-D polymeric face-sharing chains of formula PbCl3((R)–C6H5CH(CH3)NH3), PbBr3((R)–C6H5CH(CH3)NH3), PbI3((R)–C6H5CH(CH3)NH3) and PbI3((S)–C6H5CH(CH3)NH3); 1-D polymeric corner-sharing chains of formula PbCl5((±)–C6H5CH(CH3)NH3)3 and PbBr5((±)–C6H5CH(CH3)NH3)3; and 2-D corner-sharing layers of formula PbI4((S)–C6H5CH(CH3)NH3)2 and PbI4((R)–C6H5CH(CH3)NH3)2. The changes in geometry and intermolecular interactions such as hydrogen bonding and pi stacking are discussed and compared between the eight structures.

The crystal structure of complex 3, a Ni(II)(dppe) ligated in a square planar arrangement by a novel S, N-ligand, has been determined at 123 K. The neutral and air stable complex is of interest as it shows an apparently zwitterionic structure, one counter-anion to the Ni(II) being delocalised into the backbone of the ligand. Support for this conclusion comes from an analysis of bond lengths in the complex 3, the crystal structure of which is presented and the result of a density functional calculation performed on the complex. A discussion of the mechanism leading to the observed product is presented.

The cis and trans monosubstituted cyclopentadienyl tungsten and molybdenum complexes (η 5 -C 5 H 4 R)M(CO) 2 (L)I ( 1 ) (M=W, R=Me, t Bu, L=P(O i Pr) 3 , PPh 3 ; M=Mo, R=Me, L=PPh 3 ) have been synthesised and fully characterised by elemental analysis and IR and NMR spectroscopy. It was found that 1 underwent a thermal solid-state ligand isomerisation reaction and that the favoured direction of the isomerisation reaction is related to the melting points of the cis and trans isomers, i.e., with intermolecular forces in the solid state. No obvious relationship between the melting point and the metal, the ring-substituent or the ligand was observed. Crystal structure determinations of the cis and trans isomers of (η 5 -C 5 H 4 Me)W(CO) 2 (PPh 3 )I reveal that a limited amount of isomer conversion can be accommodated in the unit cell of the trans isomer, prior to crystal fragmentation. The rearrangement of the molecules within the unit cell, during isomerisation, also leads to disorder in the crystal.

[reaction: see text] N-Phenylsulfonylpyrrole 1 is magnesiated by treatment with isopropylmagnesium chloride and catalytic diisopropylamine. Reaction with various electrophiles, including palladium-catalyzed aryl- and heteroaryl cross-coupling, provides 2-substituted phenylsulfonylpyrroles in moderate to good yields.

The isomerisation of ttt -RuCl 2 (RNC) 2 (PPh 3 ) 2 (R=2,6-xylyl, t Bu, i Pr, benzyl, 2-OMe-4-Clphenyl) to cct -RuCl 2 (RNC) 2 (PPh 3 ) 2 has been carried out in the solid state. The reaction is first order and kinetic measurements have yielded activation energies of 210 kJ mol −1 (R= t Bu) and 221 kJ mol −1 (R=benzyl) for reactions performed between 160 and 180 °C. XRD analysis of the solid state reaction of ttt -RuCl 2 ( t BuNC) 2 (PPh 3 ) 2 has revealed that the cct -isomer produced is a polymorph of that produced by recrystallisation of the pure cct -RuCl 2 ( t BuNC) 2 (PPh 3 ) 2 isomer. A possible mechanism for the isomerisation reaction involving rotation of the two small groups (Cl, RNC) is proposed.