Synthesis, crystal structures, and electrochemical properties of metal complexes based on 1,10-phenanthroline-5,6-dione

Two new isomorphic metal complexes, [M(phon)(H2O)4]·SO4·2H2O (M = Ni and Zn, 1-Ni and 1-Zn, respectively, phon = 1,10-phenanthroline-5,6-dione), were crystallized at room temperature. Single-crystal X-ray analyses reveal that a metal ion is coordinated with one phon ligand and four coordinated water molecules into a discrete coordination structure which expands into a 3D supramolecular structure via hydrogen bonding interactions. The thermal and electrochemical properties of the complexes are investigated. The results show that 1-Ni exhibits redox activity under alkaline conditions and has potential to act as a redox reaction mediator, while 1-Zn does not. The specific capacitance of 1-Ni0.5Zn0.5, obtained by mixing the two complexes under hydrothermal condition, is four times higher than that of 1-Ni.