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Acyclovir, an antiviral purine derivative listed on the WHO's Model List of Essential Medicines, is commonly used in several different dosage forms from tablets to gels, oleogels and suspensions. Although temperature driven phase transitions of its commercially available 3 : 2 hydrate have been known since 2011, information on the solvent driven phase transitions of this drug has been limited. This study identifies the pathways of transformations of acyclovir forms I and V induced by organic solvents and water using the method of solution mediated phase transformation. The 3 : 2 hydrate, form V, undergoes dehydration to anhydrous form I in methanol, ethanol and N,N-dimethylformamide. Form I converts to anhydrous form II in dry methanol and N,N-dimethylformamide, while increased water content in the solvent prevents the transformation of form I to form II. Both forms I and V yield a gel-like material in dimethyl sulfoxide, composed of highly crystalline form II and reported here for the first time. Furthermore, significant differences in the thermal dehydration process of forms V and VI were observed using VT FTIR, including the first time report on a novel metastable ACV form VII formed upon dehydration of ACV dihydrate (form VI). High resolution solid-state NMR spectra of two anhydrous polymorphs (forms I and II) and two hydrates (forms V and VI) supported by DFT calculations using the CASTEP code are also presented.

Phenylalanine is an important amino acid both biologically, essential to human health, and industrially, as a building block of artificial sweeteners. Our interest in this particular amino acid and its derivatives lies with its ability to form gels in a number of solvents. We present here the studies of the influence of halogen addition to the aromatic ring on the gelation properties and we analyse the crystal structures of a number of these materials to elucidate the trends in their behaviour based on the halogen addition to the aromatic group and the interactions that result.

Microporous organic polymers (MOPs) have been prepared via one-pot polycondensation reactions between aldehydes and amines. Primary amines were reacted with imines to produce porous polymers from A2 + B2 monomer combinations. The resulting networks exhibit BET surface areas in the range 500–600 m2 g−1. This approach opens up the possibility of synthesising MOPs using readily-available and inexpensive precursors.

Mesostructured and mesoporous boroaluminophosphates (BAPO's) were synthesised using cationic templating in the presence of boric acid. The products were characterised by X-ray diffraction, 27Al, 31P and 11B solid-state NMR, thermal and elemental analysis, and nitrogen adsorption. Boron is incorporated into the structure, leading to a decrease in the degree of condensation of the inorganic component and to reduced thermal stability. Both tetrahedral and trigonal B is present in the structure of as-synthesised and calcined BAPO, but the B(4)–B(3) ratio is significantly reduced upon calcination. The kinetics of product formation were studied, and the likely mechanism of the synthesis is suggested, involving the formation of boroaluminophosphate oligomers which then react with the surfactant cations.

Mesostructured and mesoporous MgAPOs and MgAPSOs were synthesised using cationic templating in the presence of various relative amounts of Mg2+ and the silica source. The products were characterised by X-ray diffraction, 27Al, 31P and 29Si solid-state NMR, thermal and elemental analyses and nitrogen adsorption. Magnesium is incorporated into the structure substituting for either the Al3+ units or the surfactant cations, with a consequent decrease of mesoscopic ordering. Incorporation of large amounts of magnesium in either mesostructured AlPO or SAPO gives products with significantly larger pore diameters than those of MgAPO and MgAPSO with lower Mg content, or AlPO or SAPO made using the same P2O5:Al2O3 ratio. Introduction of Si into the framework leads to an increased degree of condensation of the inorganic framework, and improves the thermal stability of the products.

Solid-state NMR has been used to monitor the conformation and mobility of the organic surfactant occluded in aluminophosphate-based mesocomposites with hexagonal (Hex) and lamellar (L) structures. At ambient temperature hexagonal aluminophosphates (AlPO's) show predominant disordered gauche conformation of the aliphatic chains. On the other hand, in the mesolamellar L1 and L3 the surfactant is in the ordered all-trans conformation, while in L2 it is in the gauche conformation despite the well-defined mesolamellar structure. The temperature of the all-trans⇔gauche transition increases in the series: Hex-1, Hex-2

Mesostructured AlPO's with different structures synthesized ia the cationic templating pathway have been characterized using 1H–31P cross-polarization/magic angle spinning (CP/MAS) NMR. Hexagonal (Hex) materials have much faster CP kinetics than lamellar (L) materials, which is reflected in shorter cross-polarization times (TPH) and proton relaxation times in the rotating frame (T1ρH). TPH increases with the increasing degree of condensation of the inorganic component, which is consistent with the increased 1H–31P distance. The CP dynamics of P sites connected to the surfactant head groups are affected by the fast motions of the protons in the –N(CH3)3 group. Measurements of T1ρH indicate the microdomain structure of Hex-1, Hex-2 and L3, and two components with different proton relaxation rates have been identified. The fast relaxing component is attributed to protons within the inorganic network (mainly water molecules and OH groups coordinated to octahedral Al sites), while the component with the slower relaxation rate represents 1H atoms at the inorganic/organic interface and from the organic component. The slower CP kinetics in mesolamellar AlPO's are caused by the particular structure of the inorganic network, consisting of tetrahedral Al with only a few protons located mainly at the inorganic/organic interface, that participates in the polarization transfer.

Hexagonal (Hex-1, Hex-2 and Hex-3) and lamellar (L1 and L3) mesostructured aluminophosphates have been prepared at room temperature in the presence of a cationic surfactant. Transitions between different structures can be directed by modifying the behaviour of the surfactant and the degree of condensation of the inorganic component. The products differ in Al:P ratios, relative contents of 4- and 6-coordinate Al, degrees of condensation, template contents and thermal stabilities. The inorganic component in hexagonal and L3 products is less condensed than in L1 and L2 (previously synthesised at hydrothermal conditions) as evidenced by the predominant 6-coordination of Al and the low-field 31P NMR chemical shifts. Upon calcination, Hex-1 and Hex-2 give thermally stable mesoporous solids with a tubular pore arrangement. The pore diameter of the calcined hexagonal AlPO increases with the increased Al:P ratio.

Mesoporous silicates have been prepared from synthesis mixtures with different acid contents using Triton XN surfactants with short poly(ethylene oxide) (PEO) chains. At very high acid contents, even Triton X45 (nEO = 5.0) with a very low cloud point, gives mesoporous solids. Triton X114 (nEO = 8.0) and Triton X100 (nEO = 10.0) give high quality (HQ) products within a well-defined range of acid contents. HQ products give sharper XRD peaks and narrower pore size distributions than low quality (LQ) products. We attribute the formation of the HQ products to the altered organisation of the surfactant and the formation of hydrogen-bonded adducts with the PEO chains. The N2 adsorption–desorption parameters of the solids obtained by calcining silica–Triton XN mesophases are governed by the hydrophilicity of the surfactant, which in turn depends on the length of the PEO chains and on the acid content. Increased hydrophilicity leads to a decrease in the surface area, adsorption volume and pore diameter of the products.

High surface area porous poly(phenylene butadiynylene) networks were obtained (BET surface area up to 842 m(2) g(-1)) by the palladium-catalyzed homocoupling of 1,3,5-triethynylbenzene and 1,4-diethynylbenzene.

Two mesolamellar aluminophosphates, designated L1 and L2, were synthesised by supramolecular templating from solutions containing a cationic surfactant. Optimal synthesis conditions have been established. XRD diffraction, solid-state NMR, FTIR, thermogravimetry and SEM reveal structural differences between the two materials. The synthesis of L2 requires higher temperatures than for L1 and involves an induction period.

The hydrothermal reaction between 1,3,5-benzenetricarboxylic acid (trimesic acid, H3BTC) and 1,2-bis(4-pyridyl)ethane (BPE), in the presence of cadmium(II) ions, results in the formation of a novel layered salt, in which the organic cations and water molecules occupy spaces between anionic layers of trimesic acid.

Microporous organic polymers have been synthesised from aniline using Friedel–Crafts alkylation. Networks synthesised solely from aniline were non-porous to nitrogen. However, co-polymerisation with benzene resulted in networks with apparent Brunauaer-Emmett-Teller (BET) surface areas up to 1100 m2 g−1. Increased aniline content in the hyper-crosslinked networks led to improved CO2/N2 selectivity, suggesting a strategy for the design of materials for post-combustion carbon capture.

Conjugated microporous polymers (CMPs) based on the electron-withdrawing 1,3,5-triazine node (TCMPs) were synthesized by palladium-catalyzed Sonogashira-Hagihara cross-coupling. The porosity in these polymers was found to be comparable to the analogous 1,3,5-connected benzene CMP systems that we reported previously, demonstrating that nodes can be substituted in these amorphous materials in a rational manner, much as for certain crystalline porous metal–organic frameworks. The CO2 adsorption properties of the TCMPs were measured and compared with the corresponding CMPs, and it was found that the TCMP networks adsorbed more CO2 than CMP analogues with comparable BET surface areas. Network TNCMP-2 showed the highest surface area (995 m2 g−1) and a CO2 uptake of 1.45 mmol g−1 at 1 bar at 298 K. The band gap in these triazine-based CMPs could also be engineered through copolymerization with other functional monomers.

A homochiral three-dimensional zinc aspartate has been synthesised via reflux and solvothermal methods, which due to the coordinative flexibility of zinc displays three distinct coordination geometries and three coordination modes of aspartic acid to zinc.

Post-synthetic derivatisation of a porous material produces a functionalized material that binds the metal complex V(O)acac2, in contrast to the unfunctionalized precursor, which is inactive for complex binding.

The cyclotriphosphazene P(3)N(3)Cl(6) reacts with six equivalents of DMAP (4-(dimethylamino)pyridine) in superheated chloroform to form crystals of composition [P(3)N(3)(DMAP)(6)]Cl(6).19CHCl(3) comprising [P(3)N(3)(DMAP)(6)](6+) ions, which host five chloride ions in basket-type cavities on either side of the ring and at equatorial positions via tetradentate ortho-H-donor arrangements.

Periodic mesoporous organosilicas with –CH2–CH2– bridges and different amounts of aluminium have been synthesised using a one-step templating method with cationic surfactants. The retention of aluminium in the hybrid organosilica framework was ensured by the template removal procedure with much lower concentrations of HCl in ethanol in comparision with typically used methods. The template-extracted solids display large surface area (above 800 m2 g−1) and pore volume (above 1.13 cm3 g−1) and aluminium in predominantly tetrahedral coordination. The coupling of Al(4) with –CH2–CH2– bridges on the pore surface might offer new prospects for the application of periodic mesoporous organosilicas in catalysis.