A novel symmetrical mononuclear zinc complex: synthesis, crystal structure, Hirshfeld surface analysis, DFT calculations, and application in a supercapacitor electrode

Abstract

The development of supercapacitor electrodes based on metal complexes constitutes an interesting step toward different biomedical applications. In this context of research, a new Zn(DHA)₂(DMSO)₂ complex based on dehydroacetic acid (DHA) and dimethyl sulfoxide (DMSO) has been synthesized and structurally characterized. Suitable crystals for X-ray diffraction were collected by slow evaporation at room temperature. Single-crystal X-ray analysis revealed that the zinc ions bind through two carbonyl groups of the DHA ligand, and the titled complex is formed in a 1 : 2 metal–ligand stoichiometric ratio with an octahedral coordination geometry. Detailed Hirshfeld surface analysis and two-dimensional fingerprint plots were used to explore the intermolecular interactions in the material, and they revealed that the most significant contributions to the crystal packing are from H⋯H (45.5%), H⋯O/O⋯H (36.0%) and H⋯C/C⋯H (16.1%). In addition, using the DFT calculation method, the global descriptors are computed from the HOMO–LUMO orbitals, and the molecular reactivity sites are analyzed from an electrostatic potential map. Furthermore, an electrochemical study was carried out to estimate the energy storage capacity performance of the Zn(DHA)₂(DMSO)₂/graphene oxide (GO) hybrid material at a mass ratio of 100:1 which is sufficient for applications in many implantable health systems. The electrochemical results indicate that the Zn(DHA)₂(DMSO)₂/GO modified electrode exhibits excellent pseudo-capacitive behavior, with a specific capacitance of 36.40 F g⁻¹ at 0.2 mA g⁻¹ and a high specific energy (445 W h kg⁻¹) at a high current (1 mA g⁻¹). Excellent cycling stability with a specific capacitance retention of 105% after 2000 charge–discharge cycles at 10 mA g⁻¹ was also observed. In summary, the Zn(DHA)₂(DMSO)₂/GO modified electrode can be explored as a supercapacitor electrode that can be applied in energy storage devices for biomedical electronics dedicated to health monitoring.