Structural characterization and comparative analysis of polymorphic forms of psilocin (4-hy-droxy-N,N-di-methyl-tryptamine).

The title compound, C12H16N2O, is a hy-droxy-substituted mono-amine alkaloid, and the primary metabolite of the naturally occurring psychedelic compound psilocybin. Crystalline forms of psilocin are known, but their characterization by single-crystal structure analysis is limited. Herein, two anhydrous polymorphic forms (I and II) of psilocin are described. The crystal structure of polymorphic Form I, in space group P21/c, was first reported in 1974. Along with the redeterm-ination to modern standards and unambiguous location of the acidic H atom and variable-temperature single-crystal unit-cell determinations for Form I, the Form II polymorph of the title compound, which crystallizes in the monoclinic space group P21/n, is described for the first time. The psilocin mol-ecules are present in both forms in their phenol-amine tautomeric forms (not resolved in the 1974 report). The mol-ecules in Forms I and II, however, feature different conformations of their N,N-dimethyl ethyl-ene substituent, with the N-C-C-C link in Form I being trans and in Form II being gauche, allowing the latter to bend back to the hydroxyl group of the same mol-ecule, leading to the formation of a strong intra-molecular O-H⋯N hydrogen bond between the hydroxyl moiety and ethyl-amino-nitro-gen group. In the extended structure of Form II, the mol-ecules form one-dimensional strands through N-H⋯O hydrogen bonds from the indole group to the oxygen atom of the hydroxyl moiety of an adjacent mol-ecule. Form II exhibits whole-mol-ecule disorder due to a pseudo-mirror operation, with an occupancy ratio of 0.689 (5):0.311 (5) for the two components. In contrast, Form I does not feature intra-molecular hydrogen bonds but forms a layered structure through inter-molecular N-H⋯O and O-H⋯N hydrogen bonds.

An ortho-rhom-bic polymorph of 2-(1,3,5-di-thia-zinan-5-yl)ethanol or MEA-di-thia-zine.

Substituted triazines are a class of compounds utilized for scavenging and sequestering hydrogen sulfide in oil and gas production operations. The reaction of one of these triazines under field conditions resulted in the formation of the title compound, 2-(1,3,5-di-thia-zinan-5-yl)ethanol, C5H11NOS2, or MEA-di-thia-zine. Polymorphic form I, in space group I41/a, was first reported in 2004 and its extended structure displays one-dimensional, helical strands connected through O-H⋯O hydrogen bonds. We describe here the form II polymorph of the title compound, which crystallizes in the ortho-rhom-bic space group Pbca as centrosymmetric dimers through pairwise O-H⋯N hydrogen bonds from the hydroxyl moiety to the nitro-gen atom of an adjacent mol-ecule.

Nifedipine-pyrazine (2/1).

In the title compound, 2C(17)H(18)N(2)O(6)·C(4)H(4)N(2) [systematic name: 3,5-dimethyl 2,6-dimethyl-4-(2-nitro-phen-yl)-1,4-di-hydro-pyridine-3,5-dicarboxyl-ate-pyrazine (2/1)], the complete pyrazine molecule is generated by crystallographic inversion symmetry. The center of the pyrazine ring lies on an inversion center. The nifedipine mol-ecules are linked into chains along the c axis through N-H⋯O hydrogen bonds, while the pyrazine mol-ecules are organized in the structure through van der Waals inter-actions.

Three isostructural solvates of finasteride and their solid-state characterization.

Three crystalline hemi-hydrate, channel solvates (classified as solvates from here on) of finasteride (N-(1,1-di-methylethyl)-3-oxo-4-aza-5 alpha-androst-1-ene-17beta-carboxamide) have been obtained and fully characterized. The acetone, methyl ethyl ketone (MEK), and toluene solvates of finasteride, described herein, were found to be isostructural and belong as additional members to a family of previously reported finasteride solvates. Vacuum drying at 85 degrees C for 1 day produced the metastable, anhydrous Form II of finasteride from all three solvated materials.

Supramolecular chemistry of fluoroanions: selectivity in weak interactions.

Interactions of a chiral, calixarene-based cationic Pd(II) catalyst with [BF(4)](-) and [PF(6)](-) anions have very different consequences, association with the former giving rise to capsule formation.

Pharmaceutical Cocrystals and Their Physicochemical Properties.

This review article will highlight and discuss the advances made over the last 10 years pertaining to physical and chemical property improvements through pharmaceutical cocrystals and, hopefully, draw closer the fields of crystal engineering and pharmaceutical sciences.

Supramolecular synthesis based on a combination of hydrogen- and halogen bonds.

A family of supramolecular reagents containing two different binding sites, pyridine and amino-pyrimidine, were allowed to react with iodo- or bromo-substituted benzoic acids in order to assemble individual molecules into larger architectures with precise intermolecular interactions, using a combination of hydrogen- and halogen-bonds. The hydrogen-bond based amino-pyrimidine/carboxylic acid or amino-pyrimidinium/carboxylate synthons are responsible for the assembly of the primary structural motif in every case (7/7 times, 100% supramolecular yield), while Icdots, three dots, centeredN, Brcdots, three dots, centeredN, and Icdots, three dots, centeredO, halogen bonds play a structural supporting role by organizing these supermolecules into extended 1-D and 2-D architectures (5/7 times, 71% supramolecular yield). These results illustrate how two different non-covalent interactions can be employed side-by-side in the reliable construction of extended molecular solid-state networks with predictable connectivity and dimensionality.

C-pentyltetra(3-pyridyl)cavitand: a versatile building block for the directed assembly of hydrogen-bonded heterodimeric capsules.

Hydrogen-bond-directed assembly of heterodimeric cavitand-based capsules is of considerable interest. Herein, we report the synthesis and single-crystal X-ray structure determination of a pyridyl-functionalized cavitand that contains suitable hydrogen-bond acceptor moieties for the construction of asymmetric cavitand-based capsules. [structure: see text]

Directed supramolecular assembly of Cu(II)-based "paddlewheels" into infinite 1-D chains using structurally bifunctional ligands.

The construction of Cu(II)-containing supramolecular chains is achieved by combining suitable anionic ligands (for controlling the coordination geometry and for creating a neutral building block) with four new bifunctional ligands containing a metal-coordinating pyridyl site and a self-complementary hydrogen-bonding moiety. Seven crystal structures are presented and in each case, the copper(II) complex displays a "paddlewheel" arrangement, with four carboxylate ligands occupying the equatorial sites, leaving room for the bifunctional ligand to coordinate in the axial positions. The supramolecular chemistry, which organizes the coordination-complexes into the desired infinite 1-D chains, is driven by a combination of N-H...N and N-H...O hydrogen-bonds in five of the seven structures.

Directed supramolecular assembly of infinite 1-D M(II)-containing chains (M = Cu, Co, Ni) using structurally bifunctional ligands.

The directed assembly of six different M(II) complexes (M = Cu, Co, and Ni) into infinite chains has been achieved by combining anionic chelating ligands (for controlling the coordination geometry) with bifunctional ligands containing a metal-coordinating pyridyl moiety and a self-complementary hydrogen-bonding moiety. Six crystal structures are presented, and in each case, the chelating acac ligand occupies the four equatorial coordination sites leaving room for the bifunctional ligand to coordinate in the axial positions. The supramolecular chemistry, which organizes the coordination complexes into the desired infinite 1-D chains, is driven by a combination of N-H...N and N-H...O hydrogen bonds.

Anion control of the self-assembly of 2,3-diarylpyrazines with silver(I) salts.

The synthesis and characterization of three one-dimensional coordination polymers formed on self-assembly of 2,3-diarylpyrazines with silver(I) salts are presented. A linear double-stranded coordination polymer was formed on self-assembly of 2,3-bis(3'5'-dimethylphenyl)pyrazine with silver(I) tetrafluoroborate. An essentially linear double-strand coordination polymer was formed on self-assembly of 2,3-bis(3'5'-dimethylphenyl)pyrazine with silver(I) trifluoromethanesulfonate. In contrast a helical silver-pyrazine coordination polymer with extensive intrastrand pi-stacking was formed on self-assembly of 2,3-diphenylpyrazine with silver(I) trifluoroacetate.

Silver(I) coordination chemistry of 2,6-diarylpyrazines. Pi-stacking, anion coordination, and steric control.

The silver(I) coordination chemistry of 2,6-diarylpyrazines is reported. Discrete coordination complexes and two-dimensional coordination networks were characterized. The substitution pattern on the pendant aryl groups controlled the type of coordination chemistry involved. Thus, o-methyl-substituted aryl groups held the aryl groups orthogonal to the central pyrazine ring, opening the "hindered" nitrogen atoms to complexation, and polymeric networks were characterized. In the absence of the o-methyl groups, discrete coordination complexes were characterized. Thus, a dimeric 2:1 ligand-silver(I) complex was isolated and characterized on reaction of 2,6-bis(3',5'-dimethylphenyl)pyrazine with silver(I) trifluoroacetate in acetonitrile solvent, while a 2:2 complex was isolated from dichloromethane solvent. Two trifluoroacetate ligands bridge two silver cations in both complexes. Reaction of the same pyrazine ligand with silver(I) tetrafluoroborate yielded a discrete 2:1 complex. A 2:1 complex was isolated on reaction of 2,6-diphenylpyrazine with silver(I) nitrate. These complexes were interlinked by weakly coordinating nitrate anions to form interwoven one-dimensional ribbons. Two-dimensional networks were obtained on reaction of silver(I) trifluoroacetate with either 2,6-bis(2',6'-dimethylphenyl)pyrazine or 2-(2',6'-dimethylphenyl)-6-(3',5'-dimethylphenyl)pyrazine. The networks comprised pyrazine-silver(I) strands cross-linked with complex bridged silver(I) trifluoroacetates.