CeIII-Functionalized Polyoxotungstates: Discrete vs Extended Architectures

Abstract

Four polyoxotungstate solid state structures comprising discrete and polymeric architectures based on CeIII complexes of monolacunary Wells-Dawson-type anions [α2-PV2WVI17O61]10–, isolated as [NMe4]7Li4K3[{Ce(H2O)3(α2-P2W17O61)}2]·35H2O (KLT-1), [NMe4]8Na2[Ce(H2O)7]2[{Ce(CH3COO)(H2O)4(α2-P2W17O61)}2]·32.5H2O (NT-2), [NMe4]8K0.5Na1.5[Ce(H2O)7]2[{Ce(H2O)1.5(CH3COO)(α2-P2W17O61)}2]·22H2O (KNT-3), and [NMe4]3Li[Ce(H2O)7][Ce(H2O)4(α2-P2W17O61)]·15H2O (LT-4), illustrate the structural flexibility of CeIII ions, here imparted by their variable coordination numbers, with respect to their incorporation into polyoxometalate clusters versus their role in intercluster bridging in the solid state. While KLT-1 comprises discrete dimeric {CeP2W17}2 clusters, NT-2 and KNT-3 represent coordination polymers of linear {(Ce)(CeP2W17)}n strands, every two of which are paired via acetate bridges to yield a ladder-like topology. Finally, LT-4 features the same {(Ce)(CeP2W17)}n strands but in alternating orientation, enabling the formation of a 2D net. The title compounds have been isolated and fully characterized via single-crystal and powder X-ray diffraction, elemental and thermogravimetric analyses, IR spectroscopy, and SQUID magnetometry. The discrete polyanion [{Ce(H2O)3(α2-P2W17O61)}2]14– (1) exhibits considerable stability in aqueous medium and interesting electrochemical behavior associated with redox transitions of its CeIII and WVI centers.