Two Lanthanide-Substituted Polyoxometalates Featuring Novel Crescent-Shaped Ln5 Clusters: Structures, Ion Conductivities, and Magnetic Properties

By adopting trilacunary [A-α-GeW9O34]4– as precursor under hydrothermal conditions, two novel polyoxometalates (POMs) substituted by crescent-shaped Ln5 clusters, namely, Na4K4(H2pip)6(H2O)10{Ln10(μ3-OH)2(H2O)10[α(1,8)-GeW10O38]2[β(4,11)-GeW10O38]2}·29H2O (1-La for Ln = La, 1-Ce for Ln = Ce, pip = piperazine) were successfully synthesized. The one-dimensional chains of two lanthanide substituted POMs are constructed from edge-sharing of nanoclusters with size of 2.5 × 2.9 × 1.0 nm3, which contain two crescent-shaped five-nuclearity Ln5 clusters and two [β(4,11)-GeW10O38]12– polyanions. Furthermore, 1-La exhibits good ion-conducting performance with proton conduction activation energy of 0.49 eV, which follows vehicular mechanism. 1-Ce illustrates anti-ferromagnetic behavior, which can be attributed to spin–orbital coupling interactions within the crescent-shaped Ln5 clusters.