Chemical and electrochemical oxidation and reduction of dithizone

A non-aqueous electrochemical study of dithizone, H2Dz, 1, is compared with the chemical oxidation and reduction profile of this versatile ligand. Chemical oxidation of 1 by I2 initially leads to an isolatable disulfide-bridged species, (HDz)2, 22, but ultimately monomeric dehydrodithizone, Dz, 3, is formed. Electrochemically, in CH2Cl2/0.1 mol dm−3 [N(nBu)4][B(C6F5)4], two oxidation processes are observed for 1. Evidence of the electrochemical formation of the dimer 22 was found, but on a CV timescale the fully oxidized species, 22oxidized, did not convert to the chemically stable species 3. Regeneration of 1 during an irreversible electrochemical reduction of the electrochemically generated fully oxidized species, 22oxidized, was detected. Two further one-electron electrochemical irreversible reduction steps were also identified to ultimately generate H3Dz−, 8, one of the synthetic precursors to 1. In contrast, resolution and identification of the electron transfer steps of 1 in both dimethylsulfoxide, DMSO, or in CH2Cl2/0.1 mol dm−3 [N(nBu)4][PF6] were hampered by solvation and ion paring of [PF6]− especially with the oxidized species of 1. A metathesis of water-soluble potassium dithizonate, KHDz, 4b, led to lipophilic [N(nBu)4][HDz], 4c.

An electrochemical study of dithizone, H2Dz, in CH2Cl2/0.1 mol dm−3 [N(nBu)4][B(C6F5)4] showed that it can be oxidized in two separate one-electron transfer processes and reduced in two one-electron reduction processes; electrochemical results of H2Dz are related to its chemical electron transfer profile; a new lipophilic dithizone salt, [N(nBu)4][HDz] is described.Figure optionsDownload as PowerPoint slide