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The two-component compound formed by codeine and cyclopentobarbital was produced using grinding techniques and through evaporation from alcoholic solutions. The cocrystal nature of this phase was established unequivocally through single crystal X-ray structure determination. The asymmetric unit contains one formula unit. In the cyclopentobarbital molecule, the cyclopentenyl ring is disordered over two positions related by a rotation of approximately 180° about its C—C bond to the pyrimidine ring. The two NH groups of the cyclopentobarbital molecule form N—H⋯N and N—H⋯O bonds to piperidine and hydroxyl groups, respectively, belonging to different codeine molecules. In addition, the hydroxyl and methoxy groups of neighboring codeine molecules are linked by O—H⋯O interactions, resulting in a H-bonded framework structure of codeine and cyclopentobarbital molecules. The cocrystal was also characterized using thermal analysis, X-ray powder diffraction and IR spectroscopy. [ABSTRACT FROM AUTHOR]

In the isoxaflutole molecule {systematic name: (5-cyclopropyl-1,2-oxazol-4- yl)[2-(methylsulfonyl)-4- (trifluoromethyl)phenyl] methanone; C15H12F3NO4S}, the 1,2-oxazole and methanone fragments form an almost coplanar unit, whereas the methanone and phenyl mean planes are inclined by an angle of more than 60°. This conformation differs fundamentally from all other known examples of the 1,2-oxazol-4-yl(phenyl)methanone fragment and is ascribed to the presence of the bulky methylsulfonyl para substituent at the phenyl ring. PIXEL calculations reveal that the largest contributions to the stabilization of the crystal persist within a columnar arrangement of molecules along the twofold screw axis and in interactions between adjacent columns related by an inversion operation. Both these intra-column and inter-column motifs are dominated by the dispersion energy term but also display additional significant stabilization effects as a result of three short intermolecular C--H--O contacts involving the methanesulfonyl-O atoms. [ABSTRACT FROM AUTHOR]

The NMR spectra of polymorphs I, II, and III of the pharmaceutical drug compound phenobarbital are discussed in relation to the crystal structures. Whilst some features can be explained by inspection of the structures, others require more detailed work. In this paper, shielding computations for the [sup.13]C, [sup.15]N, and ¹H nuclei using crystallographic repetition (with optimization of the positions of all atoms) are presented. These have enabled the majority of the signals to be assigned with some confidence and several features of NMR crystallography are illuminated. In particular, resonances have been attributed separately for the three independent molecules of form I (and also for form II). Moreover, the chemically equivalent but crystallographically distinct nuclei forming the two halves of the phenyl ring (and likewise of the heteronuclear ring) have been distinguished and a structural conformational motif attached to the [sup.15]N chemical shifts revealed. The small differences between the spectra of forms I and II (which have very closely related crystal structures) are well-reproduced. The value of computations for establishing precise assignments of signals to crystallographic sites of atoms is emphasised. Conversely, the work provides a good test of the accuracy of computations for crystalline materials. Key words: NMR crystallography, phenobarbital, polymorphism, shielding computation, assignment of signals. Resume : On discute des spectres RMN des polymorphes I, II et III du phenobarbital, un compose medicamenteux, en relation avec leurs structures cristallines. Alors que certaines caracteristiques peuvent etre expliquees par l'examen des structures, d'autres demandent un travail plus detaille. Dans ce travail, on rapporte des calculs de blindage des noyaux [sup.13]C, [sup.15]N et ¹ H a l'aide de repetitions cristallographiques (avec optimisation des positions de tous les atomes). Ces resultats ont permis d'attribue pratiquement tous les signaux avec un certain degre de confiance et plusieurs caracteristiques de la cristallographie par RMN sont mis en lumiere. En particulier, les resonances ont pu etre attribuees separement pour les molecules independantes de la forme I (ainsi que de la forme II). De plus, on a pu etablir une distinction entre les noyaux chimiquement equivalents, mais distincts d'un point de vue cristallographique, des deux moities du noyau phenyle (de meme que pour le noyau heteronucleaire) et mettre en evidence un motif conformationnel attache aux deplacements chimiques du [sup.15]N. Les petites differences entre les spectres des formes I et II (dont les structures cristallines sont tres semblables) sont bien reproduites. On met en relief la valeur des calculs dans l'etablissement d'attributions precises de signaux a des sites cristallographiques d'atomes. Et en consequence, ce travail fournit un bon test de la precision des calculs pour des materiaux cristallins. Mots-cles : cristallographie par RMN, phenobarbital, polymorphisme, calcul de blindage, attribution de signaux. [Traduit par la Redaction], Introduction Phenobarbital (5-ethyl-5-phenyl-2,4,6(1H,3H,5H)-pyrimidinetrione), [C.sub.12][H.sub.12][N.sub.2][O.sub.3], is a well-known barbiturate drug, which is still in clinical use nearly a century after first being put on the market. It has the molecular structure [...]

The acid-base reaction of solid-state forms of the nonsteroidal antiinflammatory drug indomethacin with ammonia gas is studied. The extent of this reaction and the lattice changes of the crystal forms are studied by X-ray powder diffraction, optical microscopy, gravimetry and spectroscopic methods.

The X-ray structure determination of two single crystals of octamethylferrocenium tetrafluoroborate [OMFc(super +)BF(sub 4)(-)] revealed conformational polymorphism with ligand twist angles of 180 degrees and 108 degrees respectively. Temperature-dependent Moessbauer spectroscopy of (super 57)Fe-labeled [OMFc(super +)BF(sub 4)(-)] over the range 90 < T < 370 K did not show the anomalous sudden increase in the motion of the metal atom as observed in neutral OMFc.