organic compounds
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The title compound, C16H14O5·2H2O [systematic name: 5-hydroxy-2-(4-hydroxyphenyl)-7-methoxychroman-4-one dihydrate], is a natural phytoalexin flavone isolated from the native chilean species Heliotropium taltalense and crystallizes with an organic molecule and two water molecules in the asymmetric unit. The 5-hydroxy group forms a strong intramolecular hydrogen bond with the carbonyl group, resulting in a six-membered ring. In the crystal, the components are linked by O—HO hydrogen bonds, forming a three-dimensional network. The 4-hydroxyphenyl benzene ring is bonded equatorially to the pyrone ring, which adopts a slightly distorted sofa conformation. The title compound is the hydrated form of a previously reported structure [Shoja (1990). Acta Cryst. C46, 1969–1971]. There are only slight variations in the molecular geometry between the two compounds.
metal-organic compounds
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The title compound, [Cu(C5H3N2O2)0.88(C6H4NO2)1.12]n, is characterized by disorder of the anion, resulting from a statistical occupation in a 0.44 (3):0.56 (3) ratio of pyrazine-2-carboxylate and pyridine-2-carboxylate. The compound was isolated during attempts to synthesize a mixed-ligand coordination polymer by solvothermal reaction between copper(II) nitrate and equimolar mixtures of pyrazine-2-carboxylic acid and pyridine-2-carboxylic acid in a mixture of water and EtOH. The difference in the two components of the compound is due to substitutional disorder of a CH group for one of the N atoms of the pyrazine ring which share the same site in the structure. In the crystal structure, the CuII atom lies on an inversion centre and is six-coordinated in a distorted N2O4 geometry. The carboxylate group carbonyl O atoms are weakly coordinated to an equivalent CuII atom that is translated one unit cell in the a-axis direction, thus forming a polymeric chain through carboxylate bridges.
organic compounds
Open access
In the title compound, C13H13N3O, the NNCO unit forms dihedral angles of 35.8 (1) and 84.0 (1)° with the benzene and phenyl rings, respectively. The dihedral angles between the aromatic rings is 61.2 (1)°. An intramolecular N—HO hydrogen bond occurs. In the crystal, molecules are linked by weak N—HO hydrogen bonds into C(4) chains parallel to the c axis. Neighbouring chains are linked by weak N—HN hydrogen bonds, forming R44(20) rings, and resulting in the formation of a two-dimensional network lying parallel to (010). The packing also features π–π stacking interactions between phenyl rings [centroid–centroid distance = 3.803 (2) Å].