Transition metal quinone-thiosemicarbazone complexes 2: Magnetism, ESR and redox behavior of iron (II), iron (III), cobalt (II) and copper (II) complexes of 2-thiosemicarbazido-1,4-naphthoquinone

Reactions of naphthoquinone-thiosemicarbazone with Fe(II), Fe(III), Co(II) and Cu(II) yields thionato and thiolato complexes under two different conditions. Magnetic, Mössbauer and EPR measurements reveal unusual magnetic properties for the ferrous and ferric complexes with stabilization of intermediate spin-states, while there exists a significant amount of covalent character in the copper-ligand bonding. These complexes possess metal-centered redox behavior with the iron (III) complexes exhibiting a reversible Fe(III)/Fe(II) redox couple at a fairly positive potential.