Oxidation resilient dithizones – Synthesis, cyclic voltammetry and DFT perspectives

Towards improving the resistance of dithizone against oxidation, a series of halogenated derivatives were synthesized. The synthetic limit at which fluorination permanently alters the properties of dithizone was found in the transition from mono- to difluorophenyl substituted dithizones. Relative to unsubstituted dithizone, the ortho-fluoro- and difluorophenyl derivatives exhibit a decline in molar absorptivity, which increasingly renders it less effective in its traditional application as trace metal analysis reagent. By the use of cyclic voltammetry, oxidation resilience was quantified, with largest positive shift in first oxidation peak potential found for 3-fluorodithizone (279 mV). DFT calculated HOMO and LUMO energies of the dithizone derivatives were related to corresponding oxidation (Epa,1) and reduction potentials (Epc,C). Correlations between EHOMO and Epa,1, and ELUMO and Epc,C yielded R2 values of 0.98 and 0.95, respectively. Computed molecular orbital and time dependent DFT oscillator renderings agree closely with experimental observations.

The limits of oxidation resilient dithizones were explored synthetically. Redox peak potentials were measured by means of cyclic voltammetry and related to corresponding DFT computed HOMO and LUMO energies.Figure optionsDownload as PowerPoint slide