Never-Ending Story: New Cyclodextrin-Based Metal-Organic Framework Crystal Structures Obtained Using Different Crystallization Methods.

Six novel cyclodextrin (CD)-based metal-organic frameworks (MOFs) were synthesized using distinct crystallization methodologies. A modified vapor diffusion method is introduced for the first time, termed fast crystallization, which enables the rapid solid-state formation of MOF compounds. This innovative method yielded four of the newly synthesized MOFs. The crystal structures of five obtained frameworks were structurally characterized through single-crystal X-ray diffraction, while one, compound 5 (γ-CD-K-5), was additionally characterized as a bulk powder. Structural analysis revealed that two of the newly obtained MOFs, namely, compound 2 (α-CD-K-2) and compound 3 (α-CD-Rb-3), exhibited isostructural characteristics, forming a three-dimensional (3D) framework. Compound 1 (α-CD-K-1) shared the same space group as EVEGET (α-CD-K) and displayed the same framework type. Furthermore, the crystal packing of compound 4 (ß-CD-K-4) closely resembled that of compound 1 and EVEGET, with the only distinction lying in the type of CD employed. Notably, compound 6 (γ-CD-K-6) incorporated an iodine ion with an occupancy of 0.2. To discern the intermolecular interactions within the obtained MOFs, the Hirshfeld surface was calculated using Crystal Explorer software.

Crystal structure of a two-dimensional metal-organic framework assembled from lithium(I) and γ-cyclo-dextrin.

The crystal structure of the polymeric title compound, catena-poly[[[di-aqua-lithium]-µ-γ-cyclo-dextrin(1-)-[aqua-lithium]-µ-γ-cyclo-dextrin(1-)] pentadecahydrate], {[Li2(C48H79O40)2(H2O)3]·15H2O} n , consists of deprotonated γ-cyclo-dextrin (CD) mol-ecules assembled by lithium ions into metal-organic ribbons that are cross-linked by multiple O-H⋯O hydrogen bonds into sheets extending parallel to (01). Within a ribbon, one Li+ ion is coordinated by one deprotonated hydroxyl group of the first γ-CD torus and by one hydroxyl group of the second γ-CD torus as well as by two water mol-ecules. The other Li+ ion is coordinated by one deprotonated hydroxyl and by one hydroxyl group of the second γ-CD torus, by one hydroxyl group of the first γ-CD torus as well as by one water mol-ecule. The coordination spheres of both Li+ cations are distorted tetra-hedral. The packing of the structure constitute channels along the a axis. Parts of the hy-droxy-methyl groups in cyclo-dextrin molecules as well as water mol-ecules show two-component disorder. Electron density associated with additional disordered solvent mol-ecules inside the cavities was removed with the SQUEEZE [Spek (2015 ▸). Acta Cryst. C71, 9-18] routine in PLATON. These solvent mol-ecules are not considered in the given chemical formula and other crystal data. Five out of the sixteen hy-droxy-methyl groups and one water mol-ecule are disordered over two sets of sites.

The effect of excipients on the stability and phase transition rate of xylazine hydrochloride and zopiclone.

The compatibility of thermodynamically unstable polymorph of two active pharmaceutical compounds (xylazine hydrochloride form X and zopiclone form C) with different excipients was investigated. The effects of the excipient and its amount in the sample on the thermal properties and possible chemical interactions were studied. The most commonly used excipients in the pharmaceutical industry - calcium carbonate, lactose hydrate, cellulose, magnesium stearate hydrate and calcium stearate hydrate were selected for this study. The dependence of the phase transition rate from an unstable to a more stable polymorph on the excipients and their amounts in the initial sample was analysed at 80°C, and the corresponding phase transition rate constants were calculated.

Investigation of the phase transitions occurring during and after the dehydration of xylazine hydrochloride monohydrate.

This paper reports an investigation of a complex solid state phase transition where two inter-converting polymorphs (X and A) of the pharmaceutical molecule xylazine hydrochloride formed and transformed during and after the dehydration of its monohydrate (H). The crystal structures of all three forms were compared. During the investigation of this solid state phase transition it was determined that the dehydration of H produced either a pure X form, or a mixture of the X and A forms. The phase composition depended on the sample preparation procedure and the experimental conditions. It was found that grinding of the hydrate enhanced the formation of polymorph X as a product of dehydration, whereas higher humidity, temperature, or mechanical compression enhanced the formation of polymorph A. The transition mechanism of this complex process was analysed and explained by taking into account the crystal structures of these three forms.