Crystal structures of pyridinemonocarboxylic acid peroxosolvates

Polymorphism in the 1/1 Pterostilbene/Picolinic Acid Cocrystal

The crystal structures of two new polymorphs of the 1/1 pterostilbene/picolinic acid cocrystal have been analyzed by single-crystal X-ray diffraction and studied by means of DFT calculations and a set of computational tools (QTAIM, NCIplot, MEP). The observation of a new R2 2(10) synthon in each of the two polymorphs has been analyzed energetically, characterized using the topology of the electron density, and rationalized using the MEP surfaces. The exceptional bioavailability of the cocrystal is explained on the basis of BFDH morphology calculations, and the study is complemented by a deep analysis of the supramolecular synthons formed by both neutral and zwitterionic forms of picolinic acid, a versatile coformer for crystal engineering.

Crystalline Peroxosolvates: Nature of the Coformer, Hydrogen-Bonded Networks and Clusters, Intermolecular Interactions

Despite the technological importance of urea perhydrate (percarbamide) and sodium percarbonate, and the growing technological attention to solid forms of peroxide, fewer than 45 peroxosolvates were known by 2000. However, recent advances in X-ray diffractometers more than tripled the number of structurally characterized peroxosolvates over the last 20 years, and even more so, allowed energetic interpretation and gleaning deeper insight into peroxosolvate stability. To date, 134 crystalline peroxosolvates have been structurally resolved providing sufficient insight to justify a first review article on the subject. In the first chapter of the review, a comprehensive analysis of the structural databases is carried out revealing the nature of the co-former in crystalline peroxosolvates. In the majority of cases, the coformers can be classified into three groups: (1) salts of inorganic and carboxylic acids; (2) amino acids, peptides, and related zwitterions; and (3) molecular compounds with a lone electron pair on nitrogen and/or oxygen atoms. The second chapter of the review is devoted to H-bonding in peroxosolvates. The database search and energy statistics revealed the importance of intermolecular hydrogen bonds (H-bonds) which play a structure-directing role in the considered crystals. H2O2 always forms two H-bonds as a proton donor, the energy of which is higher than the energy of analogous H-bonds existing in isostructural crystalline hydrates. This phenomenon is due to the higher acidity of H2O2 compared to water and the conformational mobility of H2O2. The dihedral angle H-O-O-H varies from 20 to 180° in crystalline peroxosolvates. As a result, infinite H-bonded 1D chain clusters are formed, consisting of H2O2 molecules, H2O2 and water molecules, and H2O2 and halogen anions. H2O2 can form up to four H-bonds as a proton acceptor. The third chapter of the review is devoted to energetic computations and in particular density functional theory with periodic boundary conditions. The approaches are considered in detail, allowing one to obtain the H-bond energies in crystals. DFT computations provide deeper insight into the stability of peroxosolvates and explain why percarbamide and sodium percarbonate are stable to H2O2/H2O isomorphic transformations. The review ends with a description of the main modern trends in the synthesis of crystalline peroxosolvates, in particular, the production of peroxosolvates of high-energy compounds and mixed pharmaceutical forms with antiseptic and analgesic effects.

The crystal structure of 5-(tri-fluoro-meth-yl)picolinic acid monohydrate reveals a water-bridged hydrogen-bonding network

The title compound [systematic name: 5-(tri-fluoro-meth-yl)pyridine-2-carb-oxy-lic acid monohydrate], C7H4F3NO2·H2O, is the acid hydrate of a pyridine with a carb-oxy-lic acid group and a tri-fluoro-methyl substituent situated para to one another on the aromatic ring. The mol-ecule forms a centrosymmetric water-bridged hydrogen-bonding dimer with graph-set notation R 4 4 (12). Hydrogen-bonding distances of 2.5219 (11) and 2.8213 (11) Å are observed between the donor carb-oxy-lic acid and the bridging water acceptor, and the donor water and carbonyl oxygen acceptor, respectively. The dimers are further linked into a two-dimensional sheet via two longer inter-molecular hydrogen-bonding inter-actions between the second hydrogen atom on the bridging water mol-ecule and both a pyridine nitro-gen atom and carbonyl oxygen with distances of 3.1769 (11) and 2.8455 (11) Å, respectively. The tri-fluoro-methyl groups extend out the faces of the sheet providing for F⋯F and C-H⋯F contacts between the sheets, completing the three-dimensional packing.

Intermolecular Interactions in Functional Crystalline Materials: From Data to Knowledge

Intermolecular interactions of organic, inorganic, and organometallic compounds are the key to many composition–structure and structure–property networks. In this review, some of these relations and the tools developed by the Cambridge Crystallographic Data Center (CCDC) to analyze them and design solid forms with desired properties are described. The potential of studies supported by the Cambridge Structural Database (CSD)-Materials tools for investigation of dynamic processes in crystals, for analysis of biologically active, high energy, optical, (electro)conductive, and other functional crystalline materials, and for the prediction of novel solid forms (polymorphs, co-crystals, solvates) are discussed. Besides, some unusual applications, the potential for further development and limitations of the CCDC software are reported.

The applicability of the dimeric heterosynthon concept to molecules with equivalent binding sites. A DFT study of crystalline urea–H2O2

The limited applicability of the dimeric heterosynthon concept to a two-component urea–H₂O₂crystal is reported.