The bond distances in the mol­ecule of the title compound, C₁₉H₁₄N₂O₄, provide evidence for electronic polarization in the amino­aryl­propenone fragment and for bond fixation in the quinolinone unit. Mol­ecules are linked by N-HO and C-HO hydrogen bonds into chains in which centrosymmetric rings of R₂²(8) and R₂²(18) types alternate, and these chains are linked into sheets by a single aromatic - stacking inter­action.

4-Hydr­oxy-2-vinyl-2,3,4,5-tetra­hydro-1-benzazepine, C₁₂H₁₅NO, (I), and its 7-fluoro and 7-chloro analogues, namely 7-fluoro-4-hydr­oxy-2-vinyl-2,3,4,5-tetra­hydro-1-benzazepine, C₁₂H₁₄FNO, (II), and 7-chloro-4-hydr­oxy-2-vinyl-2,3,4,5-tetra­hydro-1-benz­azepine, C₁₂H₁₄ClNO, (III), are isomorphous, but with variations in the unit-cell dimensions which preclude in compound (III) one of the weaker inter­molecular inter­actions found in compounds (I) and (II). Thus the compounds are not strictly isostructural in terms of the structurally significant inter­molecular inter­actions, although the corresponding atomic coordinates are very similar. The azepine rings adopt chair conformations. The mol­ecules are linked by a combination of N—HO and O—HN hydrogen bonds into chains of edge-fused R³₃(10) rings, which in compounds (I) and (II) are further linked into sheets by a single C—Hπ(arene) hydrogen bond. The significance of this study lies in its observation of isomorphism in compounds (I)–(III), and its observation of a sufficient variation in one of the cell dimensions effectively to alter the range of significant hydrogen bonds present in the crystal structures.

The title compound, C₁₈H₁₂S, comprises five fused rings forming an essentially planar mol­ecule, with a total puckering amplitude (Q) of 0.032 Å and a maximum deviation from the mean plane of 0.014 (4) Å for the C atoms of the methyl­ene groups. A crystallographic mirror plane orthogonal to the mol­ecular plane passes through the S atom and the midpoint of the opposite C—C bond within the central five-membered ring. The mol­ecules lie in layers, forming edge-to-face C—Hπ inter­actions, with a separation of 2.66 Å between one H atom of the methyl­ene group and the centroid of an adjacent indene ring.

The crystal structures of the title compounds, [Ru(C₇H₉Si)₂(C₂₆H₂₄P₂)₂] and [Ru(C₄H)₂(C₂₆H₂₄P₂)₂], are described. The metal centre in both complexes has an octahedral coordination geometry, with mutually trans buta-1,3-diynyl ligands form­ing pseudo-linear ruthenium-centred polyyne chains.

The title compound, C₃₆H₃₀NP₂⁺·I^-, was obtained accidently from crystallization of a reaction mixture containing [(Ph₃P)₂N]OH and B(OH)₃, which was contaminated with MeI. There are two independent [(Ph₃P)₂N]⁺ cations and two I^- anions within the asymmetric unit. The central PNP angles are non-linear [137.6 (2) and 134.4 (2)°] and the phenyl substituents on P centres adopt different conformations within these two cations.

The structure of the title salt, C₂₄H₂₀P⁺·H₈B₃^-, at 120 (2) K has triclinic (P1) symmetry with an unusual Z = 5, although there is pseudosymmetry observed with the tetraphenylphosphonium cations exhibiting I symmetry. One of the anions is disordered over two sets of sites with refined occupancies of 0.478 (11) and 0.522 (11).

The crystal structure determination of the title compound, C₁₃H₁₅IO₄, has allowed the relative stereochemistry between the tetrasubstituted C atoms on the tetra­hydro­furan moiety to be confirmed. The title compound is a precursor of the ionophoric antibiotic Aplasmomycin. The compound is involved in both intra- and intermolecular hydrogen bonding, the latter link the mol­ecules into chains running along the b axis.

4,4′-(Phenyl­methyl­ene)bis­(6-allyl-3-chloro-2-methyl­aniline), C₂₇H₂₈Cl₂N₂, (I), and 4,4′-(2-thienylmethyl­ene)bis­(6-allyl-3-chloro-2-methyl­aniline), C₂₅H₂₆Cl₂N₂S, (II), adopt similar mol­ecular conformations, although the thienyl group in (II) exhibits orientational disorder over two sets of sites with occupancies of 0.614 (3) and 0.386 (3). The amino groups in both compounds are pyramidal. A single N—HN hydrogen bond links the mol­ecules of (I) into cyclic centrosymmetric dimers. Mol­ecules of (II) are linked by an ordered C—Hπ(arene) hydrogen bond to form cyclic centrosymmetric dimers, and these dimers are linked into statistically inter­rupted chains by a second C—Hπ(arene) hydrogen bond involving a donor in the minor component of the disordered thienyl unit.

A new crystal form of 2-methyl-6-nitro­aniline, C₇H₈N₂O₂, crystallizing with Z′ = 2 in the space group P2₁/c, has been identified during screening for salts and cocrystals. The different N—HO hydrogen-bonding synthons result in linear V-shaped chains in the new polymorph, rather than the helical chain arrangement seen in the known form where Z′ = 1. The presence of a second component during crystallization appears to have determined the resultant crystal form of 2-methyl-6-nitro­aniline.

The title compound, C₁₆H₃₆N⁺·C₂₈H₃₆N₄·F^-·CH₂Cl₂, is a calix­[4]­pyrrole macrocycle acting as a fluoride receptor by means of hydrogen bonding. Geometric comparisons with the previously published non-isostructural chloride-bound analogue are presented.

The title compound, C₄₄H₅₂N₄·C₂H₅OH, is a calix­[4]­pyrrole-type macrocycle acting as a receptor, by means of hydrogen-bond interactions to an ethanol solvent. The pyrrole groups are arranged in a 1,3-alternate conformation which gives rise to disorder in the ethanol guest, due to its ability to coordinate both above and below the plane of the macrocycle.