Organoamine-Directed Assembly of 5p–4f Heterometallic Cluster Substituted Polyoxometalates: Luminescence and Proton Conduction Properties

The assembly of heterometallic cluster substituted polyoxometalates (POMs) remains a great challenge for inorganic synthetic chemistry up to now. Herein, a series of 5p–4f heterometallic cluster substituted POMs were successfully isolated by a facile one-step hydrothermal reaction method, namely H17(H2en)3[SbIII9SbVLn3O14(H2O)3][(SbW9O33)3(PW9O34)]·28H2O(1-Ln, Ln = Ce, Sm, Eu, Gd, Tb, Dy) (en = ethylenediamine). Interestingly, by replacing en with imidazole, another series of 5p–4f heterometallic cluster substituted POMs H13(HIm)4K2Na4(H2O)9[SbIII9SbVLn3O14(H2O)3][(SbW9O33)3(PW9O34)]·26H2O (2-Ln, Ln = Sm, Eu, Gd, Tb, Dy, Im = imidazole) were obtained. Structural analyses indicate that both 1-Ln and 2-Ln are made up of an unprecedented 5p–4f heterometallic {Sb10Ln3O14(H2O)3} cluster stabilized simultaneously by mixed trilacunary heteropolyanions including {A-α-PW9O34} and {B-α-SbW9O33}. Impedance measurements indicate that both compounds exhibit different proton conduction properties, and the conductivity of 2 can reach up to 1.64 × 10–2 S cm–1 at 85 °C under 98% relative humidity. Moreover, the fluorescence emission behaviors of both compounds have been studied.