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A new polymorph (denoted polymorph II) of 3-acetyl-4-hydroxy-2H-chromen-2-one, C11H8O4, was obtained unexpectedly during an attempt to recrystallize the compound from salt-melted ice, and the structure is compared with that of the original polymorph (denoted polymorph I) [Lyssenko & Antipin (2001). Russ. Chem. Bull. 50, 418-431]. Strong intramolecular O-H...O hydrogen bonds are observed equally in the two polymorphs [O...O = 2.4263 (13) Å in polymorph II and 2.442 (1) Å in polymorph I], with a slight delocalization of the hydroxy H atom towards the ketonic O atom in polymorph II [H...O = 1.32 (2) Å in polymorph II and 1.45 (3) Å in polymorph I]. In both crystal structures, the packing of the molecules is dominated and stabilized by weak intermolecular C-H...O hydrogen bonds. Additional π-π stacking interactions between the keto-enol hydrogen-bonded rings stabilize polymorph I [the centres are separated by 3.28 (1) Å], while polymorph II is stabilized by interactions between α-pyrone rings, which are parallel to one another and separated by 3.670 (5) Å.

Whereas several studies have been made in the solid state on complexes between antimony(III) and bromide or iodide, only few complexes of antimony(III) chlorides with organic cations have been investigated. In these compounds the metal shows a tendency towards distorted octahedral coordination with some rather long Sb-Cl bonds, which is attributed to the crystalpacking forces, e.g. hydrogen bonds rather than by lone electron-pair repulsion. These compounds are interesting because they exhibit phase transitions (ferro-paraelectric) related to motions of the ammonium cations. Here, we describe the crystal structure of (4-dimethylaminopyridinium) tetrachloroanti monate(III).The complex crystals were obtained by dissolving in a concentrated HCl solution a stoichiometric mixture of 4-dimethylaminopyridine and trichloride antimony(III); the resulting aqueous solution was then kept at room temperature. After several weeks of evaporation, pseudohexagonal prismshaped monocrystals of (4-dimethylaminopyridinium)tetrachloroantimonate(III) appeared in the solution. Chemical analyses of antimony atoms and chloride anions were carried out. 5 The experimental conditions used for single-crystal data collections are reported in Table 1. The positional parameters for the antimony atoms were obtained from a three-dimensional Patterson map, while the remaining atoms were found from a successive difference Fourier map. After introducing anisotropic thermal displacement parameters for the non-hydrogen atoms, the hydrogen atoms were localized and optimized to fixed positions. Their contributions were isotropically introduced into the calculation, but not refined. The final atomic coordinates are given in Table S1 (supporting information).The final anisotropic full-matrix least squares resulted in a convergence of the R factor to 0.0316, incorporating the weighting scheme w = 1/[s 2 (Fo 2 ) + (0.0746P) 2 ] + 0.8242P], where P = (Fo 2 + 2Fc 2 )/3.The molecular structure of the (4-dimethylaminopyridinium)-tetrachoroantimonate is shown in Fig. 1. The crystal structure consists of 4-dimethylaminopyridinium cations and polynuclear anions in which distorted SbCl6 octahedron sharing cis edges are interconnected into chains (Fig. 2). The [SbCl4] -anions share two cis edges with two other neighboring octahedra, and a skew infinite chain is formed parallel to the c axis at x = 0, y = 0 and x = 0.5, y = 0.5. Each Sb atom is surrounded by six Cl atoms, forming a distorted octahedral configuration with Cl-Sb-Cl X-ray Structure Analysis Online Synthesis and Crystal Structure of (4-Dimethylaminopyridinium)-tetrachoroantimoniateAfef GHOUILI, Najla CHAARI, † and Fatma ZOUARI Laboratoire des Sciences des Matériaux et d'Environnement, Faculté des Sciences de Sfax, BP 802, 3018 Sfax, TunisiaThe salt tris(4-dimethylaminopyridinium)tetrachoroantimonate C7H11Cl4N2Sb crystallizes at room temperature in the monoclinic system with space group C2/c. The unit-cell dimensions are: a = 13.6692 (5)

In the title mol­ecule, C18H12O4, the phenyl ring is twisted by 23.2 (1)° from the mean plane of the chromene system. In the crystal, weak inter­molecular C—H⋯O hydrogen bonds link mol­ecules into zigzag chains extending in the [010] direction. An intra­molecular O—H⋯O hydrogen bond is also present.

4-hydroxy-3-methoxyphenyl-4-hydroxycoumarin chalcone (C19H14O6) was synthesized by the Claisen–Schmidt reaction with the condensation of 3-acetyl-4-hydroxycoumarin with 4-hydroxy-3-methoxybenzaldehyde (vanillin). The new compound was characterized by Fourier transform infrared microscopy, UV–vis 1H, and 13C NMR spectroscopy and its crystal structure was ab initio determined from laboratory X-ray powder diffraction data. The crystal structure is monoclinic with unit-cell parameters a = 14.3181(4), b = 8.040 71(9), c = 13.5524(3), β = 100.3559(13)°, V = 1534.84(6) Å3, and space group P21/c.