Two crown-ether-coordinated caesium halogen salts.

The crystal structures of two crown-ether-coordinated caesium halogen salt hydrates, namely di-µ-bromido-bis[aqua(1,4,7,10,13,16-hexaoxacyclooctadecane)caesium(I)] dihydrate, [Cs2Br2(C12H24O6)2(H2O)2]·2H2O, (I), and poly[[diaquadi-µ-chlorido-µ-(1,4,7,10,13,16-hexaoxacyclooctadecane)dicaesium(I)] dihydrate], {[Cs2Cl2(C12H24O6)(H2O)2]·2H2O}n, (II), are reported. In (I), all atoms are located on general positions. In (II), the Cs(+) cation is located on a mirror plane perpendicular to the a axis, the chloride anion is located on a mirror plane perpendicular to the c axis and the crown-ether ring is located around a special position with site symmetry 2/m, with two opposite O atoms exactly on the mirror plane perpendicular to the a axis; of one water molecule, only the O atom is located on a mirror plane perpendicular on the a axis, while the other water molecule is completely located on a mirror plane perpendicular to the c axis. Whereas in (I), hydrogen bonds between bromide ligands and water molecules lead to one-dimensional chains running along the b axis, in (II) two-dimensional sheets of water molecules and chloride ligands are formed which combine with the polymeric caesium-crown polymer to give a three-dimensional network. Although both compounds have a similar composition, i.e. a Cs(+) cation with a halogen, an 18-crown-6 ether and a water ligand, the crystal structures are rather different. On the other hand, it is remarkable that (I) is isomorphous with the already published iodide compound.

Mono-, di-, and oligonuclear complexes of Cu(II) ions and p-hydroquinone ligands: syntheses, electrochemical properties, and magnetic behavior.

Four highly soluble square-planar Cu(II) and Ni(II) complexes of siloxy-salens (2SiCu, 2SiNi) and hydroxy-salens (2Cu, 2Ni) have been synthesized. An X-ray crystal structure analysis was performed on 2SiCu, 2SiNi, and 2Ni. The compounds have been investigated by cyclic voltammetry, UV-vis-NIR spectroelectrochemistry, and EPR spectroscopy. According to these results, the monooxidized species [2SiCu]+ and [2SiNi]+ are to be classified as Robin-Day class II and III systems, respectively. Magnetic measurements on the dinuclear (PMDTA)Cu(II) complex 1Cu2 x (PF6)2 with deprotonated 1,4-dihydroxy-2,5-bis(pyrazol-1-yl)-benzene (1) linker revealed antiferromagnetic coupling between the two Cu(II) ions thereby resulting in an isolated dimer compound. Coordination polymers [1Cu]n(H2O)(2n) of Cu(II) ions and bridging p-hydroquinone linkers were obtained from CuSO4 x 5 H2O and 1,4-dihydroxy-2,5-bis(pyrazol-1-yl)benzene. X-ray crystallography revealed linear chains running along the crystallographic a-direction and stacked along the b-axis. Within these chains, the Cu(II) ions are coordinated by two pyrazolyl nitrogen atoms and two p-hydroquinone oxygen atoms in a square-planar fashion.

Synchrotron-radiation study of the two-leg spin-ladder (VO)2P2O7 at 120 K.

The crystal structure of the ambient-pressure phase of vanadyl pyrophosphate, (VO)2P2O7, has been precisely determined at 120 K from synchrotron X-ray diffraction data measured on a high-quality single crystal. The structure refinement unambiguously establishes the orthorhombic space group Pca2(1) as the true crystallographic symmetry. Moreover, it improves the accuracy of previously published atomic coordinates by one order of magnitude, and provides reliable anisotropic displacement parameters for all atoms. Along the a axis, the structure consists of infinite two-leg ladders of vanadyl cations, (VO)2+, which are separated by pyrophosphate anions, (P2O7)4-. Parallel to the c axis, the unit cell comprises two alternating crystallographically inequivalent chains of edge-sharing VO5 square pyramids bridged by PO4 double tetrahedra. No structural phase transition has been observed in the temperature range between 300 and 120 K.