Cryst.Growth Des. (2010), 10, 2465

​S. Long, T. Li, Cryst. Growth Des., 10, 2465-2469, 2010.
​Two different hydrogen-bonding synthons (acid-acid and acid-pyridine) are present in the crystal structures of 2-(phenylamino)nicotinic acid. The intermolecular hydrogen-bonding motifs are determined by molecular conformation and conformational energy. The authors found that by producing derivatives with electron-withdrawing groups on the phenyl ring, it is possible to strengthen the molecule’s global π-conjugation and thus engineer only the acid-acid homosynthon to be present in the crystal packing.

Cryst.Growth Des. (2010), 10, 2571

​S. Varughese, S.M. Draper, Cryst. Growth Des., 10, 2571-2580, 2010.
​A series of mono-, 1,4-di-, and 1,3,5-tripyridylpyridazines have been synthesized and analyzed. With increasing aromatic substitution and thereby steric hindrance, a systematic transition has been observed from close-packed to porous solvated assemblies. Distinct morphologies of the organic nano/microparticles, obtained by the precipitation method, indicate that the molecules interact with the solvent system in different ways.

CrystEngComm (2010), 12, 1186

​R. Centore, A. Carella, A. Tuzi, A. Capobianco, A. Peluso, CrystEngComm, 12, 1186-1193, 2010.
​A theoretical, statistical and crystallographic analysis of the H-bonding patterns in organic monohydrazides is presented. Essentially, four intermolecular H-bonding patterns are suggested to be feasible based on the most favourable conformation - two forming chains, C(4) and C22(8), and two forming rings, R22(10) or R22(6). The frequency of occurrence of the four patterns in the set of crystal structures of hydrazides retrieved from CSD was evaluated. The crystal structures of four new benzohydrazides having additional H-bonding donor or acceptor groups in the para position are presented and discussed with reference to the H-bonding patterns.

CrystEngComm (2010), 12, 64

​J.-B. Arlin, A. Johnston, G. J. Miller, A. R. Kennedy, S. L. Price, A. J. Florence, CrystEngComm, 12, 64–66, 2010.
​10,11-Dihydrocarbamazepine (DHC) is a close structural analogue to carbamazepine (CBZ), a drug used in the treatment of epilepsy. It is also known that DHC occurs as an impurity in samples of carbamazepine (CBZ). As part of a wide-ranging study combining experimental studies and crystal structure prediction, DHC was predicted to exhibit multiple different stable forms based on hydrogen-bonded dimers and hydrogen-bonded chains. After 170 automated and manual solution recrystallisations, three pure forms of DHC (forms I, II and III) had been found as well as six solvates, but only the DMSO solvate contained the dimeric motif. Singles crystals of a fourth form were finally obtained by crystallisation from the vapour phase via sublimation. The structure of form IV, reported here, is shown to match a dimer-based predicted structure from the CSP search.

Cryst.Growth Des. (2010), 10, 394

​M. L. Cheney, N. Shan, E. R. Healey, M. Hanna, L. Wojtas, M. J. Zaworotko, V. Sava, S. Song, J. R. Sanchez-Ramos, Cryst. Growth Des., 10, 394-405, 2010.
​This study is focussed on the discovery of novel crystal forms for lamotrigine, an antiepileptic drug. The pure crystalline form of lamotrigine is known to have poor solubility and dissolution rate, but is thought to be amenable to crystal engineering studies to find a multi-component form with enhanced physical properties. In this work, the authors describe the use of the supramolecular synthon approach to find ten new crystal forms of the API compound. At least one of these new forms showed promising results in subsequent pharmacokinetic studies.

Cryst.Growth Des. (2010), 10, 2229

​S. Aitipamula, P. S. Chow, R. B. H. Tan, Cryst. Growth Des., 10, 2229-2238, 2010.
​A 1:1 cocrystal involving an analgesic drug, ethenzamide (EA), and 3,5-dinitrobenzoic acid is observed to exist in two polymorphs and also forms a series of solvates. Structural analyses and desolvation information are presented for these multi-component solid forms of EA. The ability of EA cocrystals to form polymorphs and solvates is compared with general statistics extracted from the CSD on the prevalence of polymorphic and solvated cocrystals. It was found that the number of polymorphic cocrystals being added to the database is increasing, and the tendency of solvate/hydrate formation is significantly higher for cocrystals compared to single component solids.

CrystEngComm (2010), 12, 2436

​N. Schultheiss, S. Bethune, J.-O. Henck, CrystEngComm, 12, 2436-2442, 2010.
​The authors have investigated the nutraceutical compound pterostilbene for its propensity to form cocrystalline materials with active pharmaceutical ingredients. Three cocrystals of a 1 : 1 stoichiometric molar ratio of pterostilbene with caffeine (two polymorphs, Form I and Form II) and carbamazepine were prepared and characterized by crystallographic (XRPD, single-crystal) and thermoanalytical (TGA, DSC) techniques. Both of the studied cocrystals displayed enhanced stability, with respect to increasing RH, in comparison to either caffeine or carbamazepine. Additionally, the authors were able to measure the aqueous solution concentration or solubility of two cocrystals.

CrystEngComm (2010), 12, 2354

​F. P. A. Fabbiani, D. C. Levendis, G. Buth, W. F. Kuhs, N. Shankland, H. Sowa, CrystEngComm, 12, 2354-2360, 2010.
​Investigation of the crystallisation at high pressure of the gamma-amino acid drug compound gabapentin (marketed by Pfizer under the brand name Neurontin) resulted in the formation of a previously unknown heptahydrate form. This new form, the structure of which is determined by single-crystal x-ray diffraction, is determined to be reproducible at pressure but when decompressed the form dissolves. Such a highly hydrated form is suggested to be useful as a \"snapshot\" of solution behaviour at the atomic level.

Chem.Commun. (2009), , 773

​T. Friscic, L. R. MacGillivray, Chem. Commun., 773-775, 2009.
​Pseudoseeding involves templating a specific crystal structure architecture for a compound by seeding with crystals of a structurally-related, or homologous, system. In this study, the authors demonstrate the use of pseudoseeding to engineer a cocrystal with a 1D hydrogen bonded chain when otherwise the components would form a photoactive 0D hydrogen bonded assembly. The technique could potentially be used to dictate topologies of other co-crystals, thus significantly expanding the possibilites for co-crystal design.

CrystEngComm (2009), 11, 1396

​F. P. A. Fabbiani, B. Dittrich, A. J. Florence, T. Gelbrich, M. B. Hursthouse, W. F. Kuhs, N. Shankland, H. Sowa, CrystEngComm, 11, 1396-1406, 2009.
​The authors describe an study based on two goals; attempting to expand the search space for crystallisation of novel forms of a compound and tuning a specific process to achieve a desired physical form outcome. Using high pressure, new polymorphs of ciprofloxacin hemi Na salt pentahydrate and ciprofloxacin Na salt pentahydrate were obtained, some of which could be recovered to ambient pressure successfully. A previously unknown structure of anhydrous ciprofloxacin was also determined from powder diffraction data in a parallel study. Packing analyses of all the new forms obtained were peformed showing a high degree of similarity between the forms.