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The title compound,[FeCl2(C18H25N3O2)], has a distorted tetra­hedral Cl2N2 coordination of the FeII atom as a result of the constraints imposed by the 2-[2,2-bis­(4,4-dimethyl-4,5-di­hydro-1,3-oxazol-2-yl)prop­yl]pyridine ligand. The pyridine ring is almost perpendicular to the six-membered chelated ring containing the metal atom [dihedral angle between their mean planes = 88.5 (1)°].

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The title compound, C14H10N2O3, is a π-conjugated mol­ecule containing a benzoxazole aromatic fused heterobicycle. The benzoxazole ring system is planar within 0.01 Å. The mol­ecule assumes an approximately flat conformation, the benzoxazole ring system forming dihedral angles of 6.52 (12) and 7.4 (3)° with the benzene ring and the nitro group, respectively. In the crystal, mol­ecules are connected by very weak C—H...O hydrogen inter­actions, forming chains running parallel to the a or c axes. The methyl H atoms are disordered over two sets of sites of equal occupancy rotated by 60°.

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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.

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The title compound, C31H48O7·0.04CH3COOH, is a polyoxy­genated steroid obtained by selective chemical oxidation of 7-de­hydro­cholesteryl acetate. The asymmetric unit comprises three mol­ecules of the steroid (Z′ = 3) and a mol­ecule of acetic acid which has occupancy factor 0.131 (5). The geometric parameters of the independent mol­ecules do not reveal significant differences. In one mol­ecule, the terminal isopropyl group is disordered over two sets of sites with occupancy ratio 0.869 (5):0.131 (5). The three mol­ecules reveal different hydrogen-bonding patterns. Each of them is involved in an intra­molecular S(6) hydrogen-bonding motif, involving hy­droxy groups as donor and acceptor. In the crystal, two independent mol­ecules form dimers through hydrogen bonding between an OH donor and an acetate carbonyl acceptor, giving rise to R22(16) ring patterns. A single hydrogen bond between the OH group and a ketone carbonyl group is observed between two symmetry-independent mol­ecules.

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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.

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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 di­aminona­phthalene mol­ecules are slightly twisted [dihedral angles = 4.2 (2) and 3.0 (2)°] because of the steric encumbrance of NH2 groups. The perimidine and di­aminona­phthalene mol­ecules are linked by N—H...N hydrogen bonds, forming an R44(12) graph-set motif across an inversion center. In the crystal, alternating layers of the perimidine and di­aminona­phthalene mol­ecules are formed along [100]. In the perimidine layer, mol­ecules are π–π stacked along the c-axis direction with an inter­plane separation of approximately 3.4 Å.

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The title compound, C20H18O6, prepared from D-mannitol by a two-step procedure, is a functionalized fused bis-tetra­hydro­furan. In the central fragment, consisting of two fused tetra­hydro­furan rings, one O atom and its two adjacent C atoms, a methyl­ene and a bridgehead C atom, are disordered over two sets of sites with an occupancy ratio of 0.735 (9):0.265 (9). In the major component, the ring containing the disordered O atom is a half-chair conformation with twisted methylene and benzoate-substituted C atoms, whereas the other ring has a half-chair or T-form conformation. In the minor component, the ring with the disordered O atom has an envelope conformation, with the O atom as the flap, and the other ring has a half-chair conformation, with the O atom and the other bridgehead CH atom being twisted. The two aromatic rings are inclined to one another by 20.00 (12)°. In the crystal, adjacent molecules are linked via C—H...π interactions, forming chains propagating along [010].

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The title compound, C20H16O7, contains a cis-fused γ-lactone tetra­hydro­furan ring system functionalized with two benzo­yloxy groups. Both rings adopt an envelope conformation. The mol­ecule assumes an elongated shape and exibits non-crystallographic C2 symmetry. The benzo­yloxy groups are almost planar [maximum deviations of 0.0491 (15) and 0.0336 (17) Å for the O atoms] and their mean planes are inclined to one another by 16.51 (4)°. The crystal packing features weak C—H...O inter­actions. The aryl groups of adjacent mol­ecules are parallel shifted with face-to-face contacts and a shortest inter­molecular C...C distance of 3.482 (4) Å.

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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.
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