2-(4-Methyl-phen-yl)-6-nitro-1,3-benzoxazole

(E)-3-[4-(Benzo[d]oxazol-2-yl)styryl]-1-methylpyridin-1-ium trifluoroacetate

In the title molecular salt, C21H17N2O+·CF3CO2−, the dihedral angles between the benzene ring and pendant pyridyl and benzoxazole substituents of the cation are 15.35 (10) and 2.55 (9)°, respectively. In the crystal, the components are linked by weak C—H...O hydrogen bonds, C—F...π interactions and aromatic π–π stacking interactions. The F atoms of the anion are disordered over two set of sites in a 0.536 (6):0.464 (6) ratio.

Dipentyl 2,6-di-amino-benzo[1,2-b:4,5-b']di-furan-3,7-di-carboxyl-ate

The title compound, C₂₂H₂₈N₂O₆, crystallizes with one half-mol­ecule in the independent unit, the mol­ecule being located on an inversion centre. The penthyl groups are in the all-trans conformation and an almost planar conformation of the whole mol­ecule is observed [maximum deviation from the least-squares plane through all non-H atoms is 0.0229 (17) Å for an N atom]. The amino groups are involved in intra- and inter­molecular hydrogen bonds. Intra­molecular hydrogen bonding involving the amino group and ester carbonyl helps to lock the syn conformation of the ester with respect to the amino group. In the crystal, N—H⋯O hydrogen bonding involving the amino group and the furan and ester carbonyl O atoms self-assembles the mol­ecules into a two-dimensional hydrogen-bonded network parallel to (010) that displays inter­digital packing sustained by alk­yl–alkyl inter­actions.

3β,6α-Diacet-oxy-5,9α-dihy-droxy-5α-cholest-7-en-11-one

The title compound, C₃₁H₄₈O₇, a polyoxygenated steroid, was obtained by chemical oxidation of 7-de­hydro­cholesteryl acetate. The mol­ecular geometry features trans A/B and C/D junctions at the steroid core with the acetyl groups in the equatorial position and a fully extended conformation for the alkyl side chain. A chair conformation is observed for rings A and C while ring B adopts a half-chair conformation. The five-membered ring D has an envelope conformation, with the C atom bearing the methyl group at the flap. The terminal isopropyl group and one acetyl group are disordered over two sets of sites with 0.774 (8):0.226 (8) and 0.843 (7):0.157 (7) ratios, respectively. An intra­molecular S(6) O—H⋯O hydrogen-bonding motif involving a hy­droxy donor and acceptor is observed. In the crystal, chains of mol­ecules running along the b axis are formed via O—H⋯O hydrogen bonds between hy­droxy donors and carbonyl acceptors of the ordered acetyl group, giving rise to a C(14) motif. The chains are wrapped around the 2₁ screw axes.

N,N′-Dihydroxybenzene-1,2:4,5-tetracarboximide dihydrate

In the title compound, C₁₀H₄N₂O₆·2H₂O, the organic mol­ecule has crystallographically imposed inversion symmetry. The atoms of the three fused rings of the mol­ecule are coplanar within 0.0246 (8) Å, while the two hy­droxy O atoms are displaced from the mean plane of the mol­ecule by 0.127 (1) Å. In the crystal, infinite near-planar layers of close-packed mol­ecules are formed by hydrogen bonding between water O—H donor groups and carbonyl O-atom acceptors, and by weak inter­actions between C—H donor groups and water O-atom acceptors. The layers are parallel to the {102} family of planes. The stacked planes are held together by hydrogen bonding between N—OH donor groups and water O-atom acceptors.

4,5-Diamino-3-[(E,E)-4-(4,5-diamino-4H-1,2,4-triazol-3-yl)buta-1,3-dienyl]-4H-1,2,4-triazol-1-ium chloride

The title compound, C₈H₁₃N₁₀⁺·Cl⁻, is the monochlorhydrate salt of an aromatic bis­(di­amino­triazole). The cation is centrosymmetric, lying about an inversion centre (C_i symmetry) because the acidic H atom is disordered over two centrosymmetrically related ring N atoms, with equal multiplicity. It is noteworthy that protonation occurs at an N atom of the ring, instead of at the C—NH₂ or N—NH₂ amino groups. The chloride anions are also in special positions, as they lie on binary axes, and so the crystallographically independent unit contains half of a formula unit. The N atom of the C—NH₂ group is sp²-hybridized and the amino group is coplanar with the triazole ring [dihedral angle = 5 (3)°], while the N atom of the N—NH₂ amino group is pyramidal. The C=C bonds are in E conformations and the cation is flat because the conformation of the carbon chain is fully extended. The chloride anions are hexa­coordinated, in a distorted trigonal–prismatic geometry, and they are involved, as acceptors, in six hydrogen bonds. Chains of hydrogen-bonded cations, running along c and a + c, are generated by c-glide and C₂ rotation, respectively. This combination of N—H⋯Cl and N—H⋯N hydrogen bonds leads to the formation of a three-dimensional network.

Naphthalene-1,8-di-amine-2-(pyrimidin-2-yl)-1H-perimidine (2/1)

In the title adduct, C15H10N4·2C10H10N2, the pyrimidine ring is nearly co-planar with the heteroatomic perimidine ring, as indicated dihedral angle between their mean planes of 3.21 (11)°. The di-aminona-phthalene mol-ecules are slightly twisted [dihedral angles = 4.2 (2) and 3.0 (2)°] because of the steric encumbrance of NH2 groups. The perimidine and di-aminona-phthalene mol-ecules are linked by N-H⋯N hydrogen bonds, forming an R (4) 4(12) graph-set motif across an inversion center. In the crystal, alternating layers of the perimidine and di-aminona-phthalene mol-ecules are formed along [100]. In the perimidine layer, mol-ecules are π-π stacked along the c-axis direction with an inter-plane separation of approximately 3.4 Å.

3β,6β-Diacet-oxy-5,9α-dihy-droxy-5α-cholest-7-en-11-one acetic acid 0.04-solvate

The title compound, C31H48O7·0.04CH3COOH, is a polyoxy-genated steroid obtained by selective chemical oxidation of 7-de-hydro-cholesteryl acetate. The asymmetric unit comprises three mol-ecules of the steroid (Z' = 3) and a mol-ecule of acetic acid which has occupancy factor 0.131 (5). The geometric parameters of the independent mol-ecules do not reveal significant differences. In one mol-ecule, the terminal isopropyl group is disordered over two sets of sites with occupancy ratio 0.869 (5):0.131 (5). The three mol-ecules reveal different hydrogen-bonding patterns. Each of them is involved in an intra-molecular S(6) hydrogen-bonding motif, involving hy-droxy groups as donor and acceptor. In the crystal, two independent mol-ecules form dimers through hydrogen bonding between an OH donor and an acetate carbonyl acceptor, giving rise to R 2 (2)(16) ring patterns. A single hydrogen bond between the OH group and a ketone carbonyl group is observed between two symmetry-independent mol-ecules.

3,3'-({4-[(4,5-Di-cyano-1H-imidazol-2-yl)diazen-yl]phen-yl}imino)-dipropionic acid

The title compound, C₁₇H₁₅N₇O₄, is a push–pull non-linear optical chromophore containing a di­alkyl­amino donor group and the di­cyano­imidazolyl acceptor separated by a π-conjugated path. The benzene and imidazole rings are not coplanar, making a dihedral angle of 10.0 (2)°. In the crystal, mol­ecules are linked by an extended set of hydrogen bonds and several motifs are recognized. Pairs of mol­ecules are held together by hydrogen bonding between carb­oxy O—H donor groups and diazenyl N-atom acceptors, forming R₂²(24) ring patterns across inversion centres. Four-mol­ecule R₄⁴(28) ring motifs are formed, again across inversion centres, through hydrogen bonding involving carb­oxy O—H donor groups and diazenyl and imidazole N-atom acceptors. Four-mol­ecule R₄⁴(42) patterns are formed among mol­ecules related by translation and involve carb­oxy O—H and imidazole N—H donor groups with carbonyl O-atom and imidazole N-atom acceptors.