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For the pharmaceutical industry, the preformulation screening of the compatibility of drug and polymeric excipients can often be time-consuming because of the use of trial-and-error approaches. This is also the case for selecting highly effective polymeric excipients for forming molecular dispersions in order to improve the dissolution and subsequent bio-availability of a poorly soluble drug. Previously, we developed a new thermal imaging-based rapid screening method, thermal analysis by structure characterization (TASC), which can rapidly detect the melting point depression of a crystalline drug in the presence of a polymeric material. In this study, we used melting point depression as an indicator of drug solubility in a polymer and further explored the potential of using the TASC method to rapidly screen and identify polymers in which a drug is likely to have high solubility. Here, we used a data bank of 5 model drugs and 10 different pharmaceutical grade polymers to validate the screening potential of TASC. The data indicated that TASC could provide significant improvement in the screening speed and reduce the materials used without compromising the sensitivity of detection. It should be highlighted that the current method is a screening method rather than a method that provides absolute measurement of the degree of solubility of a drug in a polymer. The results of this study confirmed that the TASC results of each drug-polymer pair could be used in data matrices to indicate the presence of significant interaction and solubility of the drug in the polymer. This forms the foundation for automating the screening process using artificial intelligence.

We demonstrate the combined use of NMR-enhanced crystallography and solvent-free synthesis by accelerated aging (AA), for the discovery and structural characterization of a novel cadmium-based open metal–organic framework (MOF) belonging to the class of zeolitic imidazolate frameworks (ZIFs). Although solid-state NMR spectroscopy has been used to assist in structural characterization of crystalline solids by powder X-ray diffraction (PXRD), typically through quantification of the contents of the asymmetric unit, this work highlights how it can take a more active role in guiding structure determination, by elucidating the coordination environment of the metal node in a novel MOFs. Exploration of AA reactions of cadmium oxide (CdO) and 2-methylimidazole (HMeIm) enabled the synthesis of not only the previously reported yqt1-topology framework but also a new material (1) exhibiting a Cd/MeIm ratio of 1:3, contrasting the 1:2 ratio expected for a ZIF. Structural characterization of 1 was enabled by using 111Cd solid-state nuclear magnetic resonance (SSNMR) to provide information on the coordination environment of the cadmium node. Specifically, 111Cd SSNMR experiments were conducted on a series of model compounds to correlate the cadmium coordination environment to the observed isotropic chemical shift, δiso(111Cd), followed by multinuclear SSNMR experiments on 1 to determine the nature of the metal coordination environment and the number of distinct chemical sites. This information was used in refinement of the molecular level structure from the available PXRD data, a technique termed NMR-enhanced crystallography, revealing that 1 is an open diamondoid (dia) topology Cd(MeIm)2 framework based on Cd2+ ions tetrahedrally coordinated with MeIm– ligands and additional HMeIm guest molecules within the framework pores. Although AA was initially devised as a clean, mild route for making MOFs, these results provide a proof-of-principle of how, by combining it with SSNMR spectroscopy as a means to overcome limitations of PXRD structure determination, it can be used to screen for new solid phases in the absence of solvents, high temperatures, or mechanical impact that are inherent to other thermally-, solution-, or mechanochemically-based techniques.

This study aimed to develop a rapid, simple and inexpensive screening method for selecting the best polymeric candidates possessing high active pharmaceutical ingredient (API) miscibility during the early stages of formulation development of solid dispersion based pharmaceutical products. A new thermal imaging based method, thermal analysis by structural characterization (TASC), was used as a thermoptometeric tool in conjunction with data analysis software to detect the melting point depression and post-melting dissolution of felodipine particles screened over thin spin-coated films of ten polymers commonly used in the pharmaceutical field. On the polymeric substrates the drug showed different degrees of melting point reduction, reflecting their different levels of polymer-drug miscibility. Using TASC to detect melting point depression is significantly (20-40 times) faster than the conventional DSC method without loss of the sensitivity of detection. The quantity of the material required for the screening is less than 1/1000th of the material used in conventional DSC tests which significantly reduce the material wastage. Isothermal TASC tests and IR imaging confirmed the occurrence of thermal dissolution of the drug in the polymer for more miscible pairs. The real-time stability tests validate the accuracy of the polymer-drug miscibility screening results. These results demonstrate TASC as a promising screening tool for rapidly selecting the polymeric excipients for pharmaceutical formulations development.

Encapsulation of pharmaceuticals inside nanoporous materials is of increasing interest due to their possible applications as new generation therapeutics, theranostic platforms, or smart devices. Mesoporous silicas are leading materials to be used as nanohosts for pharmaceuticals. Further development of new generation of nanoscale therapeutics requires complete understanding of the complex host-guest interactions of organic molecules confined in nanosized chambers at different length scales. In this context, we present results showing control over formation and phase transition of nanosize crystals of model flexible pharmaceutical molecule tolbutamide confined inside 3.2 nm pores of the MCM-41 host. Using low loading levels (up to 30 wt %), we were able to stabilize the drug in highly dynamic amorphous/disordered state or direct the crystallization of the drug into highly metastable nanocrystalline form V of tolbutamide (at loading levels of 40 and 50 wt %), providing first experimental evidence for crystallization of pharmaceuticals inside the pores as narrow as 3.2 nm.

Understanding the fine details of self-assembly of building blocks into complex hierarchical structures represents a major challenge en route to the design and preparation of soft matter materials with specific properties. Enzymatically-synthesised cellodextrins are known to have limited water solubility beyond DP9, a point at which they self-assemble into particles resembling the anti-parallel cellulose II crystalline packing. We have prepared and characterized a series of site-selectively fluorinated cellodextrins of different degrees of fluorination and substitution patterns by chemoenzymatic synthesis. The structural characterization of these materials at different length scales, combining advanced NMR and microscopy methods, showed that multiply 6-fluorinated cellodextrin chains assembled into particles presenting morphological and crystallinity features that are unprecedented for cellulose-like materials. In contrast, the introduction of a single fluorine atom per cellodextrin chain had a minor impact on materials structure. Our work emphasizes the strength of combining chemoenzymatic synthesis, fluorinated building blocks and advanced NMR and microscopy methods for the thorough characterization of hierarchical structures, leading to the controlled design of new biomaterials with specific properties.

NMR-enhanced crystallography enables the characterization of a novel cadmium-based, open metal-organic framework (MOF) from a solvent-free "accelerated aging" process. Whereas accelerated aging was devised as a clean, mild route for making MOFs, these results highlight how it application in materials discovery and characterization is aided by a combination of X-ray diffraction and solid-state NMR spectroscopy.

Novel, knowledge based models for the prediction of hydrate and solvate formation are introduced, which require only the molecular formula as input. A data set of more than 19 000 organic, nonionic, and nonpolymeric molecules was extracted from the Cambridge Structural Database. Molecules that formed solvates were compared with those that did not using molecular descriptors and statistical methods, which allowed the identification of chemical properties that contribute to solvate formation. The study was conducted for five types of solvates: ethanol, methanol, dichloromethane, chloroform, and water solvates. The identified properties were all related to the size and branching of the molecules and to the hydrogen bonding ability of the molecules. The corresponding molecular descriptors were used to fit logistic regression models to predict the probability of any given molecule to form a solvate. The established models were able to predict the behavior of ∼80% of the data correctly using only two descriptors in the predictive model.

Fenofibrate is one of the most commonly prescribed hyperlipidemia agents. Despite its high lipophilicity and ultralow aqueous solubility, most commercially available formulations use micronized crystalline fenofibrate form I, which has a low dissolution rate and poor oral bioavailability. Little is known about the crystallization of other polymorphs from supercooled amorphous fenofibrate. This study reports a new fenofibrate polymorph (form III) obtained via a controlled heterogeneous nucleation method using low quantity (1% w/w) of the generally recognized as safe (GRAS) oral pharmaceutical excipient talc. Form III has a low melting point of 50 °C, and crystallization of form I immediately occurs after the melting of form III. The microscopic, thermal, and spectroscopic characterizations of form III confirmed the distinct molecular packing difference between the new form and other known forms. The discovery of this new form will enrich the understanding of the molecular behavior of fenofibrate and bring useful insights into the role pharmaceutical excipients in selective crystallization of pharmaceutical active ingredients.

Paroxetine HCl can exist as a non-stoichiometric hydrate (Form II) or as a stoichiometric hemihydrate (Form I); the latter is considered to be the stable form and its structure is well-known. However, little work has been performed to investigate its dehydration behavior, hence the generation of the anhydrous form via dehydration of Form I was investigated. A combination of thermal (differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)) and diffraction (variable temperature X-ray powder diffraction (VT-XRPD)) techniques were used. Dehydrated Form I was prepared using ultra-dry conditions and the resulting product compared to dehydrated Form II. DSC indicated that the two dehydrated forms of Form I and II had distinct melting points. TGA experiments allowed the calculation of the activation energy for the dehydration of Form I, which varies between 86?114 kJ/mol. Pawley refinement of the VT-XRPD data suggested that Form I dehydrates to an isostructural anhydrate, since the unit cell parameters of this new form were very similar to those of Form I with only a smaller volume as consequence of dehydration. Comparison with dehydrated Form II indicated that these two forms represent different crystal entities, hence a new anhydrous form of paroxetine HCl has been identified. Paroxetine HCl can exist as a non-stoichiometric hydrate (Form II) or as a stoichiometric hemihydrate (Form I); the latter is considered to be the stable form and its structure is well-known. However, little work has been performed to investigate its dehydration behavior, hence the generation of the anhydrous form via dehydration of Form I was investigated. A combination of thermal (differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)) and diffraction (variable temperature X-ray powder diffraction (VT-XRPD)) techniques were used. Dehydrated Form I was prepared using ultra-dry conditions and the resulting product compared to dehydrated Form II. DSC indicated that the two dehydrated forms of Form I and II had distinct melting points. TGA experiments allowed the calculation of the activation energy for the dehydration of Form I, which varies between 86?114 kJ/mol. Pawley refinement of the VT-XRPD data suggested that Form I dehydrates to an isostructural anhydrate, since the unit cell parameters of this new form were very similar to those of Form I with only a smaller volume as consequence of dehydration. Comparison with dehydrated Form II indicated that these two forms represent different crystal entities, hence a new anhydrous form of paroxetine HCl has been identified.

Paroxetine hydrochloride (HCl) is an antidepressant drug, reported to exist in the anhydrous form (form II) and as a stable hemihydrate (form I). In this study, we investigate the hydration behavior of paroxetine HCl form II with a view to understanding both the nature of the interaction with water and the interchange between forms II and I as a function of both temperature and water content. In particular, we present new evidence for both the structure and the interconversion process to be more complex than previously recognized. A combination of characterization techniques was used, including thermal (differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)), spectroscopic (attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR)), dynamic vapor sorption (DVS) and X-ray powder diffraction (XRPD) with variable humidity, along with computational molecular modeling of the crystal structures. The total amount of water present in form II was surprisingly high (3.8% w/w, 0.8 mol of water/mol of drug), with conversion to the hemihydrate noted on heating in hermetically sealed DSC pans. XRPD, supported by ATR-FTIR and DVS, indicated changes in the unit cell dimensions as a function of water content, with clear evidence for reversible expansion and contraction as a function of relative humidity (RH). Based on these data, we suggest that paroxetine HCl form II is not an anhydrate but rather a nonstoichiometric hydrate. However, no continuous channels are present and, according to molecular modeling simulation, the water is moderately strongly bonded to the crystal, which is in itself an uncommon feature when referring to nonstoichiometric hydrates. Overall, therefore, we suggest that the anhydrous form of paroxetine HCl is not only a nonstoichiometric hydrate but also one that shows highly unusual characteristics in terms of gradual unit cell expansion and contraction despite the absence of continuous channels. These structural features in turn influence the tendency of this drug to convert to the more stable hemihydrate. The study has implications for the recognition and understanding of the behavior of pharmaceutical nonstoichiometric hydrates.

A set of complete, reliable cocrystal structures was extracted from the Cambridge Structural Database, and molecular descriptors, usually used in quantitative structure-activity relationship studies, were calculated for each molecule. The resulting database describes pairs of molecules that form cocrystals with each other in terms of their calculated molecular properties. Statistical analysis of the data was performed to identify properties that tend to be similar or complementary for such pairs of molecules. The strongest descriptor correlations found relate to the shape and polarity of cocrystal formers. Hydrogen bond donor and acceptor counts of cocrystal formers, on the other hand, show no obvious statistical relationship.

The crystal structures of four homologous cis-alicyclic β-amino acids present a new recurring layer pattern of hydrogen bonds. This pattern was derived from two one-dimensional patterns observed in related alicyclic 2-hydroxycarboxylic acid structures. Its robustness is demonstrated by the isostructurality of the four crystals. The hydrogen bonds arrange the molecules in bilayers in the solid phase. The pattern was stressed by variations of the molecules, i.e., by the introduction of a double bond, by the change between stereoisomers, and by the replacement of the simple alicyclic ring with a bicyclic one. These variations gradually weaken the correspondence of the actual structure to the original design.

2-Arylsulfanyl and 2-benzylsulfanylpyridinium N-arylimides (2) easily prepared from 3-aryltetrazolopyridinium salts (1) with aryl and benzylthiolates, respectively, reacted with various dipolarophiles yielding cycloadducts that underwent transformation to give tetrahydropyrrolo[3,2-b]pyridines (5, 6, and 8) in good yields. A similar rearrangement (formation of 15) was also observed in the case of parent derivatives being unsubstituted in position 2 (12). The abscence of any significant solvent effect, comparison of the sulfur and non-sulfur analogues, as well as the stereoselective nature of the observed ring transformation seem to support a sigmatropic mechanism. Structure elucidation of the products has been carried out by single-crystal X-ray diffraction and (1)H NMR experiments.