Synthesis, crystal structure and property of a novel Nickel-containing tungstophosphate [Na_3(H_2O)_8{Ni_3(H_2O)(B-α-PW_9O_(34))(B-β-PW_8O_(31))}_2]~(21-)

摘要

A novel 6-Nickel-substituted tungstophosphate Na_(21)[Na_3(H_2O)_8{Ni_3(H_2O)(B-α-PW_9O_(34))(B-β-PW_8O_(31))}_2]-36H_2O(1) has been successfully synthesized in aqueous solution and structurally characterized by single-crystal X-ray diffraction, elemental analysis, TG and IR. Polyanion [Na_3(H_2O)_8{Ni_3(H_2O)(B-α-PW_9O_(34))(B-β-PW_8O_(31))}_2]~(21-) is composed of two {Ni_3(H_2O)(B-α-PW_9O_(34))(B-β-PW_8O_(31))}~(12-) subunits linked by three Na~+ ions. And each {Ni_3(H2O)(B-α-PW_9O_(34))(B-β-PW_8O_(31))}~(12-) subunit is composed of two nonequivalent Keggin fragments, [B-β-PW_8O_(31)]~(9-) and [B-α-PW_9O_(34)]~(9-) held together via three Ni~(2+) ions. Anew 1D network architecture is built up of the adjacent sandwich polyanions [Na_3(H_2O)_8{Ni_3(H_2O)(B-α-PW_9O_(34)) (B-β-PW_8O_(31))}_2]~(21-) through two Na~+ ions. The electrochemical behavior is elucidated in the pH = 5 (0.2 M Na_2HPO_4+ NaH_2PO_4) buffer solution employing cyclic voltammetry. Two reversible redox peaks correspond to the redox of the W~(VI). An investigation of the magnetic property indicates that the six nickel centers exhibit dominantly ferromagnetic exchange interaction.