Synthesis, crystal structure and battery-like studies on a new acylpyrazolone-based mixed-ligand Cu(II) complex

A new mixed-ligand Cu(II) complex, [Cu(pyr)(bpy)(OH 2 )]ClO 4 (1), was synthesized from 4-acetyl-3-methyl-1-phenyl-2-pyrazoline-5-one (H-pyr) and 2,2-bipyridine (bpy). Single-crystal X-ray diffraction, elemental analysis, and FTIR and UV–Vis spectroscopy were used to confirm its structure. The pyr ligand is the monoanionic deprotonated form of the H-pyr enol tautomer. Additionally, the complex’s battery-like capabilities were investigated. The newly synthesized complex possessed a high specific capacity and provided sufficient energy density for SC devices. Electrochemical evaluations, such as cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy (EIS), indicated that (1) with redox of metal-center holds satisfactory capacity and delivered energy when constructed in three- or two-electrode configuration (KOH 3 M). (1) displayed battery-like qualities (b-value ~ 0.88), as determined by the diffusion contribution at various scan rates. In an alkaline environment, the EIS measurements revealed a low interfacial charge resistance. The maximum specific capacity measured in the three-electrode system was 483 C g −1 (413.6 C g −1 at 2 mV s −1 ) at a current density of 1 A g −1 . These pyrazolone-based compounds would be promising candidates for further energy storage.