Solid-state synthesis of embedded single-crystal metal oxide and phosphate nanoparticles and in situ crystallization

A new solid state organometallic route to embedded nanoparticle-containing inorganic materials is shown, through pyrolysis of metal-containing derivatives of cyclotriphosphazenes. Pyrolysis in air and at 800 °C of new molecular precursors gives individual single-crystal nanoparticles of SiP2O7, TiO2, P4O7, WP2O7 and SiO2, depending on the precursor used. High resolution transmission electron microscopy investigations reveal, in most cases, perfect single crystals of metal oxides and the first nanostructures of negative thermal expansion metal phosphates with diameters in the range 2–6 nm for all products. While all nanoparticles are new by this method, WP2O7 and SiP2O7 nanoparticles are reported for the first time. In situ recrystallization formation of nanocrystals of SiP2O7 was also observed due to electron beam induced reactions during measurements of the nanoparticulate pyrolytic products SiO2 and P4O7. The possible mechanism for the formation of the nanoparticles at much lower temperatures than their bulk counterparts in both cases is discussed. Degrees of stabilization from the formation of P4O7 affects the nanocrystalline products: nanoparticles are observed for WP2O7, with coalescing crystallization occurring for the amorphous host in which SiP2O7 crystals form as a solid within a solid. The approach allows the simple formation of multimetallic, monometallic, metal-oxide and metal phosphate nanocrystals embedded in an amorphous dielectric. The method and can be extended to nearly any metal capable of successful coordination as an organometallic to allow embedded nanoparticle layers and features to be deposited or written on surfaces for application as high mobility pyrophosphate lithium–ion cathode materials, catalysis and nanocrystal embedded dielectric layers.

Impurity profiling and synthesis of precursors to the hallucinogenic amphetamine DOB

DOB (4‐bromo‐2,5‐dimethoxyamphetamine) is a newly emerging hallucinogenic amphetamine that sparked serious health warnings in Ireland, following its first seizure back in 2003. Known more commonly as “snowball”, this drug is highly potent and may be used as a substitute to ecstasy (MDMA) and lysergic acid diethylamide (LSD). To date, the work carried out on the impurity profiling of DOB is limited in comparison to amphetamine, methamphetamine and MDMA. In this work, the impurity profile of 4‐bromo‐2,5‐dimethoxyphenyl‐2‐propanone (4‐Br‐2,5‐P2P) is explored. This ketone is a direct precursor to DOB. Its more versatile non‐bromo analogue, 2,5‐ dimethoxyphenyl‐2‐propanone (2,5‐P2P) is also examined, as in addition to DOB, it may be used in the synthesis of a range of several other hallucinogenic amphetamines. A number of different routes to both 2,5‐P2P and 4‐Br‐2,5‐P2P were investigated. For each of these routes, the impurities produced were carefully isolated. Following isolation, the impurities were fully characterised (by 1H‐NMR/13C‐NMR spectroscopy, IR, MS), in order to aid structure elucidation. Compounds not easily resolved by flash column chromatography were analysed by LC‐MS and/or independently synthesised for the purpose of attaining reference standards. Adaptation of the well‐known ‘phenylacetic acid route’ to synthesis of both 2,5‐P2P and 4‐Br‐2,5‐P2P, was found to provide low yields of the expected ketone products. Four impurities were isolated during the preparation of both ketones. The yield of one of these impurities (possessing a dibenzylketone core), was greatly influenced by the amount of acetic anhydride reagent used during the reaction. Having carried out the reaction with several different equivalents of acetic anhydride, it was found that formation of the ‘dibenzylketone’ could not be eliminated. This may increase its likelihood of being detected in the final drug product. The ‘Darzens route’, having very recently emerged as a synthetic route to amphetamine and MDMA precursors, was discovered to be a viable route for manufacture of 2,5‐P2P and 4‐Br‐2,5‐P2P. Despite execution of the reaction being more tedious, the route provides superior yields (≈50–60%) to those achieved using the ‘phenylacetic acid route’ (≈35–38%). Incorporation of a bromine atom (at the aromatic 4‐position) is required at some stage during synthesis of DOB. The bromination of many intermediates/starting materials was therefore also examined in detail. Bromination of the acid starting material 2,5‐dimethoxyphenylacetic acid (2,5‐PAA) was found to be clean and high yielding. This was in stark contrast to the bromination of the benzaldehyde starting material, the ketone precursor 2,5‐P2P and the dibenzylketone‐based impurity. Numerous brominated products were isolated from each of these reactions, many of which were novel compounds, and previously unreported as impurities in the literature. The unpredictable/nondescript nature of these brominations is likely to have a significant impact on the impurity profile of illicitly produced DOB.

Synthesis of indium nanoparticles at ambient temperature; simultaneous phase transfer and ripening

The synthesis of size-monodispersed indium nanoparticles via an innovative simultaneous phase transfer and ripening method is reported. The formation of nanoparticles occurs in a one-step process instead of well-known two-step phase transfer approaches. The synthesis involves the reduction of InCl3 with LiBH4 at ambient temperature and although the reduction occurs at room temperature, fine indium nanoparticles, with a mean diameter of 6.4 ± 0.4 nm, were obtained directly in non-polar n-dodecane. The direct synthesis of indium nanoparticles in n-dodecane facilitates their fast formation and enhances their size-monodispersity. In addition, the nanoparticles were highly stable for more than 2 months. The nanoparticles were characterised by dynamic light scattering (DLS), small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared (FT-IR) spectroscopy to determine their morphology, structure and phase purity.