Tetrahedral Polyoxometalate Nanoclusters with Tetrameric Rare-Earth Cores and Germanotungstate Vertexes

Two
novel 1D copper-bridged tetrahedral polyoxometalate nanoclusters
with tetrameric rare-earth cores and germanotungstate vertexes, Na3H7­[Cu­(en)2]5­[Cu­(en)2­(H2O)]2­[RE4Ge4­W46O164­(H2O)3]·nH2O (RE = GdIII, n = 25 for 1; RE = YIII, n = 23 for 2; en = ethylenediamine),
have been hydrothermally synthesized and structurally characterized
by elemental analyses, IR spectra, thermogravimetric analysis (TGA),
and single-crystal X-ray diffraction. The most prominent structural
feature of 1 and 2 consists of unprecedented
tetrahedral RE-substituted germanotungstate nanoclusters {[(α-Ge­W11O39­RE)2­(μ3-WO4)­(α-Ge­W11O39­RE­(H2O))]­(μ4-WO4)­[α-Ge­W11O39­RE­(H2O)2]}24–, in which four mono-REIII-substituted Keggin [α-Ge­W11O39­RE­(H2O)n]5– (n = 0, 1, 2) moieties are
combined together with the aid of two WO42– connectors. What’s more interesting is that adjacent tetrahedral
nanoclusters are interconnected with each other via [Cu­(en)2]2+ bridges, forming a 1D extended chain architecture.
To our knowledge, 1 and 2 are the first
polyoxometalate-based Cu–RE containing 1D chain constructed
from tetrahedral RE-substituted germanotungstate nanoclusters and
copper–organic bridges. Furthermore, the solid-state electrochemical
and electrocatalytic properties of 1 and 2 have been carried out in 0.5 mol·L–1 Na2SO4 + H2SO4 aqueous solution
by entrapping them in a carbon paste electrode. 1 and 2 display apparent electrocatalytic activities for the nitrite
and bromate reduction.