Building solids inside nano-space: from confined amorphous through confined solvate to confined ‘metastable’ polymorph

The nanocrystallisation of complex molecules inside mesoporous hosts and control over the resulting structure is a significant challenge. To date the largest organic molecule crystallised inside the nano-pores is a known pharmaceutical intermediate – ROY (259.3 g mol1). In this work we demonstrate smart manipulation of the phase of a larger confined pharmaceutical – indomethacin (IMC, 357.8 g mol1), a substance with known conformational flexibility and complex polymorphic behaviour. We show the detailed structural analysis and the control of solid state transformations of encapsulated molecules inside the pores of mesoscopic cellular foam (MCF, pore size ca. 29 nm) and controlled pore glass (CPG, pore size ca. 55 nm). Starting from confined amorphous IMC we drive crystallisation into a confined methanol solvate, which upon vacuum drying leads to the stabilised rare form V of IMC inside the MCF host. In contrast to the pure form, encapsulated form V does not transform into a more stable polymorph upon heating. The size of the constraining pores and the drug concentration within the pores determine whether the amorphous state of the drug is stabilised or it recrystallises into confined nanocrystals. The work presents, in a critical manner, an application of complementary techniques (DSC, PXRD, solid-state NMR, N2 adsorption) to confirm unambiguously the phase transitions under confinement and offers a comprehensive strategy towards the formation and control of nano-crystalline encapsulated organic solids

A novel one-dimensional coordination polymer with Cd2+ and diethylene-triaminepentaacetic acid

catena-Poly[[[bis[diaqua(4,4′-bipyridine)cadmium(II)]-bis[μ -(N″-carboxymethyldiethylenetriamine-N,N,N′, N″-tetraacetato) cadmium(II)]]-μ-4,4′-bipyridine] tetradecahydrate], [Cd4(C14H19N3 O10)2(C10 H8N2)3 (H2O)4]· 14H2O or [Cd4(HDTPA)2(BPY)3 (H2O)4]·14H2O, where BPY is 4, 4′bipyridine and HDTPA4- is N″-carboxymethyldiethylenetriamine-N,N,-N′,N″-tetraacetate, consists of a one-dimensional coordination polymer formed from a secondary building unit which comprises four Cd centres. The chain structure of the title compound was obtained by the use of a multidentate organic ligand. N,N,N′,N″,N″-diethylenetriaminepentaacetic acid (H5DTPA), which forms multiple chelate rings with the Cd metal centres. An extended network is formed via hydrogen bonds

Synthesis of hierarchically porous silica and metal oxide beads using emulsion-templated polymer scaffolds

Uniform, hierarchically porous inorganic beads (SiO2, A1 2O3, TiO2, and ZrO2) have been produced using emulsion-templated polymer beads as templates. The polymer scaffolds were prepared by oil-in-water-in-oil (O/W/O) sedimentation polymerization (Zhang, H.; Cooper, A. I. Chem. Mater. 2002, 14, 4017). The inorganic beads were prepared by simply immersing the polymer scaffold beads in a range of inorganic precursor solutions, followed by sol-gel condensation in air and subsequent calcination of the polymer phase. The hierarchical structures are composed of mesopores (diameters 2-5 nm), micropores (in the case of silica beads), and large emulsion-templated macropores of around 5-10 μm. All of the pores are highly interconnected. The inorganic beads exhibit high macropore volumes as characterized by mercury intrusion porosimetry. Polymer-silica composite beads with micropores and high macropore volumes were also produced. These large inorganic beads (diameters 1.0-1.5 mm) are easily handled and separated and may be useful in applications such as catalysis and separation, especially for macromolecules or viscous systems where large pores are needed to improve mass transport into the pore structure

Initial stages of propane activation over Zn/MFI catalyst studied by in situ NMR and IR spectroscopic techniques

The early stages of propane activation over Zn-modified H-MFI catalysts were studied by in situ 13C MAS NMR and IR spectroscopic techniques. Propane 2-13C, propane 1-13C, deuterated propane, and deuterated dihydrogen were used as labelled reactants. Both techniques pointed to the formation of zinc propyl species at the onset of propane conversion. Moreover, formation of ZnOH groups simultaneously to zinc propyl species was evidenced by IR spectroscopic techniques. The results point to the propane activation through dissociative adsorption over zinc oxide species, followed by propene evolution and recombinative desorption of dihydrogen. Propene further oligomerizes over acidic sites, while dihydrogen either evolves as a final product or participates in propane hydrogenolysis into ethane and methane. At low partial pressure of reactants, H2 recombinative desorption and hydrogen evolution are favoured, whereas at high pressures, the hydrogenolysis route is preferable

Tuning of gallery heights in a crystalline 2D carbon nitride network

Poly(triazine imide) - a 2D layered network - can be obtained as an intercalation compound with halides from the ionothermal condensation of dicyandiamide in a eutectic salt melt. The gallery height of the intercalated material can be tuned via the composition of the eutectic melt and by post-synthetic modification. Here, we report the synthesis of poly(triazine imide) with intercalated bromide ions (PTI/Br) from a lithium bromide and potassium bromide salt melt. PTI/Br has a hexagonal unit-cell (P63cm (no. 185); a = 8.500390(68) Å, c = 7.04483(17) Å) that contains two layers of imide-bridged triazine (C3N3) units stacked in an AB-fashion as corroborated by solid-state NMR, FTIR spectroscopy and high-resolution TEM. By comparison with a recently reported material PTI/Li +Cl-, prepared from a LiCl/KCl eutectic, the layer-stacking distance in the analogous bromide material was expanded from 3.38 Å to 3.52 Å-an exceptionally large spacing for an aromatic, discotic system (cf. graphite 3.35 Å). Subsequent treatment of PTI/Br with concentrated ammonium fluoride yields poly(triazine imide) with intercalated fluoride ions (PTI/F) (P63/m (no. 176); a = 8.4212(4) Å, c = 6.6381(5) Å) as a statistical phase mix with PTI/Br. Fluoride intercalation leads to a contraction of the gallery height to 3.32 Å, demonstrating that the gallery height is synthetically tuneable in these materials