Liana Orola

Nicotinamide fumaric acid supramolecular cocrystals: diversity of stoichiometry

Synthesis of nicotinamide and fumaric acid supramolecular cocrystals with 1 : 1 and 2 : 1 amide to acid stoichiometries results in the formation of an amide–acid heterosynthon (1 : 1 stoichiometry) and an amide–amide homosynthon (2 : 1 stoichiometry) and different conformations of the fumaric acid moieties.

Protonation effects on the UV/Vis absorption spectra of imatinib: A theoretical and experimental study

An experimental and theoretical investigation of protonation effects on the UV/Vis absorption spectra of imatinib showed systematic changes of absorption depending on the pH, and a new absorption band appeared below pH 2. These changes in the UV/Vis absorption spectra were interpreted using quantum chemical calculations. The geometry of various imatinib cations in the gas phase and in ethanol solution was optimized with the DFT/B3LYP method. The resultant geometries were compared to the experimentally determined crystal structures of imatinib salts. The semi-empirical ZINDO-CI method was employed to calculate the absorption lines and electronic transitions. Our study suggests that the formation of the extra near-UV absorption band resulted from an increase of imatinib trication concentration in the solution, while the rapid increase of the first absorption maximum could be attributed to both the formation of imatinib trication and tetracation.

Spontaneous cocrystal hydrate formation in the solid state: crystal structure aspects and kinetics

Kinetics of anhydrous cocrystal hydration and that of cocrystal monohydrate formation from starting compounds in the solid state are studied as a function of RH and time. The propensity of the anhydrate to hydration is related to the crystal structures of anhydrous and hydrated forms.

The effect of pH on polymorph formation of the pharmaceutically active compound tianeptine

The anti-depressant pharmaceutical tianeptine has been investigated to determine the dynamics of polymorph formation under various pH conditions. By varying the pH two crystalline polymorphs were isolated. The molecular and crystal structures have been determined to identify the two polymorphs. One polymorph is an amino carboxylic acid and the other polymorph is a zwitterion. In the solid state the tianeptine moieties are bonded through hydrogen bonds. The zwitterion was found to be less stable and transformed to the acid form. During this investigation an amorphous form was identified.

N-(2,6-Dimethyl­anilino)-5,6-dihydro-4H-1,3-thia­zin-3-ium chloride monohydrate

In the title compound, alternatively called xylazine hydrochloride monohydrate, C12H17N2S+·Cl−·H2O, the six-membered thiazine ring is in a half-chair conformation. In the crystal structure, six component centrosymmetric clusters are formed via intermolecular O—H⋯Cl, N—H⋯O and N—H⋯Cl hydrogen bonds involving xylazine cations, chloride anions and water molecules.

The conformation of pyrogallol as a result of cocrystallization with N-heterocyclic bases

Structural analysis of the supramolecular cocrystals formed by pyrogallol with acridine, 4,4′-bipyridine, and 1,10-phenanthroline shows that the studied cocrystals are assembled via the hydroxyl–pyridine heterosynthon. In the crystal and molecular structures of these cocrystals in order to form the maximum number of hydrogen bonds, taking into consideration steric effects, the pyrogallol moiety in the supramolecular arrangement has the following conformations: with acridine - syn1, 4,4′-bipyridine - anti, and 1,10-phenanthroline - syn2. Discrete supramolecular complexes are formed by acridine–pyrogallol and the 1,10-phenanthroline–pyrogallol polymorph I. The 1,10-phenanthroline–pyrogallol polymorph II and the 4,4′-bipyridine–pyrogallol trihydrate form extended hydrogen bonded chains.

Bis(N,N′-diphenyl­benzamidinium) fumarate

The crystal structure of the title compound, 2C19H17N2 +·C4H2O4 2−, consists of centrosymmetric trimers built up of two crystallographically independent N,N′-diphenylbenzamidinium cations and one fumarate dianion, which is located on a centre of inversion. The components of the trimers are linked by N—H⋯O hydrogen bonding. In the cation, the outer rings make dihedral angles of 53.66 (5) and 78.38 (5)° with the central ring. The two outer rings make a dihdral angle of 81.49 (5)°.

Dipotassium 4,4'-(hexane-3,4-di-yl)bis-(benzene-sulfonate) dihydrate.

The anion of the title compound, also called sygethin dihydrate, 2K+·C18H20O6S2 2−·2H2O, has crystallographic inversion symmetry. The K+ cation is surrounded by eight O atoms in a distorted cubic coordination geometry, forming extended K—O—S networks. There are also O—H⋯O hydrogen bonds.