Dawson-type polyoxometalate-based silver complexes: syntheses, structures, and enhanced electrochemical capacitance modulated by transition metal coordination motifs.

Four novel Dawson polyoxometalate (POM)-based compounds were synthesized under hydrothermal conditions, [Ag(2,2'-bpy)2]5[HP2W18O62]·H2O (1), [Ag4(4,4'-bpy)4][4,4'-bpy]2[H2P2W18O62]·H2O (2), [Ag(bizm)2]6[P2W18O62]·H2O (3), and [Ag(bizm)2]2(bizm)4[H4P2W18O62]·2H2O (4), (2,2'-bpy = 2,2'-bipyridine, 4,4'-bpy = 4,4'-bipyridine, and bizm = benzimidazole), and were characterized by IR spectroscopy, UV-vis spectroscopy, powder X-ray diffraction (XRD), elemental analysis, and single-crystal X-ray diffraction analysis. Electrochemical performance tests conducted on the four compounds revealed that compound 2 exhibits the most superior capacitive properties, with a specific capacitance of 193.5 F g-1 at a current density of 1.5 A g-1. This study not only enriches the structural diversity of Dawson-POM-based compounds but also offers a viable strategy for enhancing the capacitive properties of POM-based materials.