A novel 1D zigzag chain organic–inorganic polymer with Dawson-type polyoxometalates as building blocks: synthesis and crystal structure of H1.5[Sm(H2O)8]0.5[Sm(DMF)6(H2O)(a-P2W18O62)]·DMF·3H2O

A novel 1D chain organic–inorganic polymer H1.5[Sm(H2O)8]0.5[Sm(DMF)6(H2O)(a-P2W18O62)]·DMF·3H2O with Dawson-type polyoxometalates as building blocks has been synthesized by reaction of SmCl3, DMF and a-H6P2W18O62·nH2O in the mixed solution of acetonitrile and water in the bulk ratio of 1:1 and characterized by IR, UV spectra, TG-DTA technique, electrochemical behavior and X-ray single-crystal diffraction. X-ray single-crystal structural analysis displays that the title compound crystallizes in an orthorhombic lattice, P21212 space group, with a ¼ 23:605ð5Þ; b ¼ 30:443ð6Þ; c ¼ 14:536ð3Þ A ° , a ¼ b ¼ g ¼ 908; V ¼ 10446(4) A ° 3, Z ¼ 4; R1 ¼ 0:0493; wR2 ¼ 0:0783: [Sm(1)(DMF)6(H2O)]3þ coordination cation is nine-coordinate with a distorted tricapped trigonal prismatic environment, which is bridged through W–O–Sm(1)–O–W linkages to build an unprecedented 1D zigzag linear chain structure by alternate polyoxometalate anions and metal coordination cations in the polymer, whereas [Sm(2)(H2O)8]3þ coordination ion is a discrete unit incorporated into the gaps of the polyoxoanions with an eight-coordinate square antiprismatic geometry. Cyclic voltammetry reveals that the pH of the supporting electrolytic solution has a marked effect on the electrochemical behaviors. q 2004 Elsevier B.V. All rights reserved.