Synthesis, crystal structure and property of a novel Nickel-containing tungstophosphate [Na3(H2O)8{Ni3(H2O)(B-α-PW9O34)(B-β-PW8 O31)}2]21−

A novel 6-Nickel-substituted tungstophosphate Na21[Na3(H2O)8{Ni3(H2O)(B-α-PW9O34)(B-β-PW8O31)}2]·36H2O(1) has been successfully synthesized in aqueous solution and structurally characterized by single-crystal X-ray diffraction, elemental analysis, TG and IR. Polyanion [Na3(H2O)8{Ni3(H2O)(B-α-PW9O34)(B-β-PW8O31)}2]21− is composed of two {Ni3(H2O)(B-α-PW9O34)(B-β-PW8O31)}12− subunits linked by three Na+ ions. And each {Ni3(H2O)(B-α-PW9O34)(B-β-PW8O31)}12− subunit is composed of two nonequivalent Keggin fragments, [B-β-PW8O31]9− and [B-α-PW9O34]9− held together via three Ni2+ ions. A new 1D network architecture is built up of the adjacent sandwich polyanions [Na3(H2O)8{Ni3(H2O)(B-α-PW9O34) (B-β-PW8O31)}2]21− through two Na+ ions. The electrochemical behavior is elucidated in the pH = 5 (0.2 M Na2HPO4+ NaH2PO4) buffer solution employing cyclic voltammetry. Two reversible redox peaks correspond to the redox of the WVI. An investigation of the magnetic property indicates that the six nickel centers exhibit dominantly ferromagnetic exchange interaction.

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