The novel crystal structures of seven compounds which combine 2-phenylethylammonium cations and perhalometallate anions, all with the general formula (C 8
Pharmaceutical co-crystallisation is emerging as a possible alternative to polymorphs, salts and solvates in the modification of an active pharmaceutical ingredient (API) during dosage form. It may alter the physico-chemical properties of the API (e.g. melting point and solubility), and also have intellectual property implications.Traditionally, co-crystallisation research has involved robust synthons with strong interactions and rarely involved pharmaceutically acceptable co-crystallising agents and conditions. Our current work has focused on the co-crystallisation of sulfathiazole with sugar excipients, [1], where moderate to weak interactions were expected to dominate.Co-crystallisation was investigated by solution and solid-state methods (including solvent mediated grinding). Co-crystallisation of sulfathiazole with lactose, mannitol and sorbitol was unsuccessful from solution or the solid-state. However, sulfathiazole-glucose cocrystals were produced from ethanol and propanol solutions.[1] Gavan P.T., Blagden N., Seaton C.C., Grimsey, I.M., Marshall, P., What is most likely going to happen when a homogeneous solution containing two different molecular solutes is allowed to evaporate to dryness? Unless a chemical reaction driven by the formation of covalent bonds takes place between the two solutes one would, as a rule, expect the appearance of two separate molecular solids. This is a manifestation of the inherent structural selfishness of molecules, something that is relied upon every time recrystallization is employed as a method of purification. Recrystallization processes are essential in most covalent synthetic procedures and are performed on a regular basis in every synthetic laboratory. In the supramolecular laboratory, however, the very same process also provides an opportunity to move in the opposite direction -a co-crystallization is a deliberate attempt at bringing together different molecular species in one crystalline lattice without making or breaking covalent bonds. Recrystallization and co-crystallization processes are, in essence, only distinguishable by their intents. The goal of the former is a homomeric product, the goal of the latter is a heteromeric product. Since the odds are stacked firmly in favor of a homomeric product, how do we go about developing reliable and versatile synthetic methods for the directed assembly of co-crystals? This presentation will attempt to answer the question by outlining several modular hydrogen-bond driven strategies for the design and synthesis of binary and ternary supermolecules and co-crystals. The ultimate aim of crystal engineering is the design of crystal structures, and as a result, materials with desired properties. A fundamental requirement of crystal engineering is the understanding of the role of non-covalent interactions occurring in the solid-state structure.A number of crystal engineering studies have focused on the identification of interaction synthons in compounds of the type LMX 4 where L is the 4,4'-bipyridinium cation [1] or the pyrid...
The aim of crystal engineering is the design of crystal structures, and as a result, materials with desired properties. A fundamental requirement of crystal engineering is the understanding of the role of non-covalent interactions present in the solidstate structure. This study focuses on the identification of non-covalent interactions in a family of 2-phenylethylammonium perhalometallate compounds, containing the metals Zn, Cd and Hg. A number of novel crystal structures, some isostructural, will be reported. In the compounds investigated, each ammonium group possesses three hydrogen atoms, all participating in hydrogen bonding. The hydrogen bonding-and aromatic interactions present in these crystal structures will be highlighted, and their influence on the molecular geometry and packing illustrated. Crystal engineering synthons will be identified, and compared to synthons identified in related structures.
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