Two Novel Co-Crystals of Naproxen: Comparison of Stability, Solubility and Intermolecular Interaction

Two novel co-crystals of naproxen (NPX) were designed and prepared at a stoichiometric ratio of 1:1, namely, naproxen–caprolactam (NPX–CPL) and naproxen–oxymatrine (NPX–OMT). The characteristics of the co-crystals were evaluated in terms of stability and solubility studies. In terms of solubility, in four kinds of solvent systems with different pH, the solubility of NPX–OMT was significantly improved compared with that of NPX, whereas the NPX–CPL showed advantages in acidic solvent systems, indicating that the co-crystals can be applied to concoct preparations depending on therapeutic purposes. Furthermore, the experimental results of the thermal analysis showed that the co-crystal NPX–OMT had better thermal stability than the co-crystal NPX–CPL. Finally, as a complement to the single crystal X-ray diffraction (SC XRD) method, the theoretical calculation based on density functional theory (DFT) was also used to reveal the intermolecular interaction of the co-crystals at the molecular level and visually display the difference between them.

Exploring the molecular landscape of multicomponent crystals formed by naproxen drug and acridines

Three cocrystals were obtained by naproxen and acridines, optimizing the yield to more than 99% with LAG. The two structures by solution show a host-guest structure, while that by LAG a layered one, with no interconversion between parent structures.

A Novel Mechanism of Preferential Enrichment Phenomenon Observed for the Cocrystal of (RS)-2-{4-[(4-Chlorophenoxy)methyl]phenoxy}propionic Acid and Isonicotinamide

A new entry of chiral anti-hyperlipoproteinemia drug is reported, showing an excellent preferential enrichment (PE) phenomenon which is not caused by a polymorphic transition during crystallization, but is proposed to occur by a novel mechanism involving partially irregular stacking of R and S homochiral two-dimensional (2D) sheets with a large dipole moment, followed by selective redissolution of one homochiral 2D sheet into the mother liquor during crystallization. The cocrystal composed of (RS)-2-{4-[(4-chlorophenoxy)methyl]phenoxy}propionic acid (CPPPA) and achiral isonicotinamide exhibited a substantial enrichment in the mother liquor up to 93 % ee by simply repeating recrystallization under nonequilibrium conditions using high supersaturation. Furthermore, the deposited crystals with low ee values obtained at the end of PE experiment were second harmonic generation (SHG)-positive, indicating the formation of homochiral domains in the deposited crystals, which reflects the proposed mechanism of PE.

Stoichiometric and polymorphic salt of imidazolium picrate monohydrate

The asymmetric unit of the title co-crystal salt, 1H-imidazol-3-ium 2,4,6-tri-nitro-phenolate monohydrate, C4H7N2+·C6H2N3O7-·H2O, contains one imidazolium cation, one picrate anion and one solvent water mol-ecule of crystallization. The phenolic proton has been transferred to an imidazole N atom. In the crystal, the components are linked by N-H⋯O and O-H⋯O hydrogen bonds into a three-dimensional network which is further consolidated by weak C-H⋯O hydrogen bonds. In addition, π-π stacking inter-actions occur between pairs of imidazolium cations and picrate anions. If only the classical N-H⋯O and O-H⋯O hydrogen bonds are considered, the component ions are linked into a three-dimensional threefold inter-penetrating network of the topological type utp [or (10,3)-d]. Hirshfeld surface analysis indicates the crystal structure is mainly stabilized by H⋯·O contacts of the hydrogen bonds.

Structure and physicochemical characterization of a naproxen-picolinamide cocrystal

Naproxen (NPX) is a nonsteroidal anti-inflammatory drug with pain- and fever-relieving properties, currently marketed in the sodium salt form to overcome solubility problems; however, alternative solutions for improving its solubility across all pH values are desirable. NPX is suitable for cocrystal formation, with hydrogen-bonding possibilities via the COOH group. The crystal structure is presented of a 1:1 cocrystal of NPX with picolinamide as a coformer [systematic name: (S)-2-(6-methoxynaphthalen-2-yl)propanoic acid-pyridine-2-carboxamide (1/1), C14H14O3·C6H6N2O]. The pharmaceutically relevant physical properties were investigated and the intrinsic dissolution rate was found to be essentially the same as that of commercial naproxen. An NMR crystallography approach was used to investigate the H-atom positions in the two crystallographically unique COOH-CONH hydrogen-bonded dimers. 1H solid-state NMR distinguished the two carboxyl protons, despite the very similar crystallographic environments. The nature of the hydrogen bonding was confirmed by solid-state NMR and density functional theory calculations.

Hydrogen-bonded network in the salt 4-methyl-1H-imidazol-3-ium picrate

In the title molecular salt, C4H7N2 (+)·C6H2N3O7 (-), the phenolic proton of the starting picric acid has been transferred to the imidazole N atom. The nitro groups are twisted away from the benzene ring plane, making dihedral angles of 12.8 (2), 9.2 (4) and 29.3 (2)°. In the crystal, the component ions are linked into chains along [010] via N-H⋯O and bifurcated N-H⋯(O,O) hydrogen bonds. These chains are further linked by weak C-H⋯O hydrogen bonds into a three-dimensional network. The complex three-dimensional network can be topologically simplified into a 4-connected uninodal net with the point symbol {4.8(5)}.

Z′ = 2 crystallization of the three isomeric piridinoylhydrazone derivatives of isosteviol

Inclusion of an “extra” molecule in a unit cell as a “cost” of transferring a robust mirror-symmetrical H-bonding motif from a racemic environment into a homochiral one was presented.