An organic-inorganic polymer with Dawson-type polyoxometalates as building blocks: synthesis, characterization and crystal structure of [{Pr(DMF)6} {Pr(DMF)7}(P2W18O62)] n

Abstrtact  An organic-inorganic polymer of Pr(DMF)₆Pr(DMF)₇(P₂W₁₈O₆₂)] _n has been synthesized in acetonitrile-water (5 : 2, volume ratio) mixed solvent. Single-crystal X-ray structural analysis indicates that the title compound crystallizes in a monoclinic lattice, P2₁/C, with a = 1.8574(4), b=2.3907(5), c=2.4222(5) nm, β=99.48(3)°, Z = 4, ∨=10.609(4) nm³, D _c =3.501 Mg/m³, F(000)=9972, R₁=0.0654 and wR ₂= 0.1098. The result of crystal structure analysis reveals that Pr³⁺(1) complex ion is eight-coordinated with a distorted bicapped trigonal prismatic environment, which is combined with the heteropolyanion by terminal oxygen atom, whereas Pr³⁺(2) complex ion is also eight-coordinated with a distorted square antiprismatic environment, which is linked to the heteropolyanion by terminal oxygen atom. Adjacent structure units of Pr(DMF)₆Pr(DMF)₇(P₂W₁₈O₆₂)] are bridged through W-O-Pr1-O-W links to form an unprecedented one-dimensional zigzag linear chain by alternate polyanions and cationic units in the polymer. Thermal analysis reveals that the framework of the title polyanion decomposes at 613.8°C.