Contributions of secondary alcohol-ketone O-H...O=C and furan-acetate Csp2-H...OOC synthons to the supramolecular packings of two bioactive molecules.

The crystal structures of rubescin D (1, C26H30O5) and monadelphin A (2, C30H36O11), bioactive molecules of the vilasinin and gedunin classes of limonoids, respectively, are reported for the first time and the synthons affecting their crystal packings are analyzed on the basis of their occurrences in molecules in the Cambridge Structural Database that share the same moieties. Rubescin D, 1, crystallizes in the space group P21 and its molecular structure consists of three six-membered rings A, C and D having, respectively, envelope, twist-boat and half-chair conformations, and three five-membered rings with half-chair (B and E) and planar conformations (F). Many synthons found in the crystal packing of 1 are in agreement with expectations derived from molecules displaying the same moieties. However, the secondary alcohol-ketone O-H...O=C synthon, which has a low occurrence (2.9%), contributes much to the layered packing, while the furan-ketone Csp2-H...O=C and secondary alcohol-epoxide O-H...OC2 synthons usually found in these compounds (occurrences of 20.6 and 17.6%, respectively) are missing. The packing of 1 is close to that of ceramicine B (3), but is completely different from that of TS3 (4), suggesting that the absence of the epoxide group in 3 would have favoured the furan-secondary alcohol Csp2-H...OH synthon and that the missing hydroxy group in 4, a strong hydrogen-bond donor, would have favoured the involvement of water molecules in the crystal packing. The molecular structure of monadelphin A, 2, consists of four six-membered fused rings (A, B, C and D) and one five-membered ring (E); they have twist-boat (A and C), chair (B), screw-boat (D) and planar (E) conformations. The molecule crystallizes in the space group P212121 with the contribution of many synthons usually found in compounds having the same moieties. However, the secondary alcohol-acetate O-H...OOC and secondary alcohol-ketone O-H...O=C synthons (occurrences of 16.7% each in these compounds) are missing. The furan-acetate Csp2-H...OOC synthon not observed in these compounds greatly contributes to the layered packing of 2. The layered packing is very close to those of 7-oxogedunin (5) and 6-dehydro-7-deacetoxy-7-oxogedunin (6), which both crystallize in the space group P21.

Crystal structure of di-ammonium bis-[tris-(oxamide dioxime-κ2 N,N')nickel(II)] bis-[tris-(oxalato-κ2 O,O')chromate(III)] 6.76-hydrate.

The asymmetric unit of the title compound, (NH4)2[Ni(C2H6N4O2)3]2[Cr(C2O4)3]2·6.76H2O, comprises two NH4 + cations, two [Ni(C2H6N4O2)3]2+ cations and two [Cr(C2O4)3]3- anions, as well as eight water mol-ecules of crystallization of which only one is fully occupied. In the cationic and anionic complexes, the central atoms (NiII and CrIII) are each surrounded by three bidentate ligands (N-chelating oxamide dioxime and O-chelating oxalate, respectively), resulting in distorted octa-hedral coordination spheres. In the crystal, O-H⋯O hydrogen bonds between the oxamide dioxime ligands as donor groups and the oxalate ligands as acceptor groups alternately connect the cationic and anionic complexes into infinite pillars extending parallel to [100]. Moreover, N-H⋯O hydrogen bonds between the same ligands connect neighboring pillars, thus delineating channels that accommodate the charge-balancing NH4 + cations as well as the water mol-ecules of crystallization. Although the H atoms could not be localized for these two species, the corresponding N⋯O and O⋯O distances indicate hydrogen bonds of medium strength.

Hexa-aqua-nickel(II) bis-[tri-aqua-µ3-oxalato-di-µ-oxalato-bariumchromate(III)] tetra-hydrate.

The title compound, [Ni(H2O)6][BaCr(C2O4)3(H2O)3]2·4H2O, was obtained in the form of single crystals from the slow evaporation of an aqueous mixture of {Ba6(H2O)17[Cr(C2O4)3]4}·7H2O and NiSO4·6H2O in the molar ratio 1:4. Its structure is made up of corrugated anionic (101) layers of formula [BaCr(C2O4)3(H2O)3] n n - that leave voids accommodating the charge-compensating cations, [Ni(H2O)6]2+ (point group symmetry ), as well as the water mol-ecules of crystallization. The anionic layers are built from the connection of barium and chromium atoms through bridging oxalate ligands. The CrIII atom is hexa-coordinated by O atoms of three oxalate ligands while the BaII atom is tenfold coordinated by three O atoms of water mol-ecules and seven O atoms of four oxalate ligands. Each NiII atom sits on an inversion center and is coordinated by six water mol-ecules. One of the uncoordinated water mol-ecules is disordered over two sites, with a refined occupancy ratio of 0.51 (5):0.49 (5). In the crystal, extensive O-H⋯O hydrogen-bonding inter-actions link the anionic layers, the charge-balancing cations as well as the water mol-ecules of crystallization into a three-dimensional supra-molecular network.