Synthesis, characterization and crystal structure of a novel 2D network structure based on hexacopper(II) substituted tungstoantimonate

The dimeric, hexacopper(II) substituted tungstoantimonate NaK6[Cu6Cl(SbW9O33)2] · 14H2O (1a) has been synthesized in good yield using a one-pot procedure by reaction of Cu2+ ions with the trilacunary precursor salt Na9[α-B-SbW9O33] and characterized by IR spectroscopy, UV electronic spectroscopy, cyclic voltammetry and single-crystal X-ray diffraction. The title polyanion represents the first tungstoantimonate substituted by six copper centers and the polyanion as basic building unit is assembled into a two-dimensional network-like complex by Cu–Odouble bond; length as m-dashW bonds. The electrochemical behavior of 1a was investigated in buffer solution (pH 3.0) by cyclic voltammetry. In the potential range between −0.7 and 0.6 V, the compound exhibits the successive redox processes of the addenda atoms (W) followed by the redox reaction originating from the substituted CuII, which revealed the stepwise reduction of Cu2+ centers within the polyanion 1 before deposition of Cu0 on the glassy carbon electrode surface. The compound 1a is shown to have electrocatalytic properties towards the reductions of nitrate and nitrite.