Synthesis, structure, and electrochemical potential of a 3d − 4f heterobimetallic polyoxometalate

A three-dimensional (3-D) 3d-4f polyoxometalate (POM), [Gd2Cu(SiW12O40)(Hpca)4(pca)4(H2O)3]·(Hpca)2·H2O (1) (Hpca = isonicotinic acid, abbreviated as Cu-Gd-CP), was synthesized by hydrothermal method and characterized by XRD, TG, IR, and Ultraviolet–visible (UV–vis) spectra. The Gd3+ ions have two different coordination modes, which correspond to distinct kinds of dinuclear secondary building units, ([Gd12(Hpca)4(pca)4(H2O)2] and [Gd22(Hpca)4(pca)4(H2O)4]). Thus, there are two different types of pores (pore A and pore B) filled by free Hpca molecules in Cu-Gd-CP. The Hpac molecules in pore A are oriented perpendicular to each other in pore B. The electrochemical potential of Cu-Gd-CP is explored.