Two polymolybdate-based hybrid compounds constructed from monodentate imidazolated naphthalene ligand with capacitive performance

Abstract

The development of polyoxometalate-based hybrid compounds offered a hopeful opportunity to develop capacitor electrode materials. Herein, two new polyoxometalate-based hybrid compounds, [Cu(4 − INCN)₂(ε − Mo₈O₂₆)_0.5] (1) and [Zn(H₂O)(4 − INCN)₃(β − Mo₈O₂₆)_0.5], were synthesized under hydrothermal condition by using 4 − imidazol − 1 − yl − naphthalene − 1 − carbonitrile (4 − INCN) as N-donor ligand. The [ε − Mo₈O₂₆]⁴⁻ and [β − Mo₈O₂₆]⁴⁻ anions were involved in the structures of two compounds, respectively. Compound 1 displayed a two-dimensional layer structure, where the [ε − Mo₈O₂₆]⁴⁻ anions were gathered by Cu (II) ions to produce a two-dimensional structure with the 4 − INCN as monodentate organic ligands hanged on the both sides. In the structure of compound 2, the aggregation of [β − Mo₈O₂₆]⁴⁻ and Zn (II) ions resulted in a one-dimensional chain, which was decorated by the 4-INCN ligands through coordination with Zn (II) ions. Two compounds as electrode materials provided specific capacitances of 1092 F g^–1 for 1 and 731 F g^–1 for 2 at the current densities of 1 A g^–1, and showed excellent capacitance retention rates after 1000 cycles. These findings provided a possible approach in the preparation of POM-based hybrid compounds employed as capacitor electrode materials.