Solvation effects in the electrochemistry of diphenylpicrylhydrazyl

摘要

The electrochemistry of diphenylpicrylhydrazyl (DPPH) was studied in nitromethane, nitrobenzene, benzonitrile, acetonitrile, acetone, methanol, ethanol, propanol-2,N,N-dimethylformamide,N,N-dimethylacetamide, and dimethylsulfoxide employing cyclic voltammetric technique. Reversible behaviour was observed for the systemsDPPH/DPPH+andDPPH/DPPH−in all solvents on the platinum microelectrode. The variation of ΔEform=(Eoxidationform−Ereductionform) upon solvent can be well described by a complementaryLewisacid—base model for solvent—solute interactions: ΔEform=−3.685DN−4.537An+651.84 with a correlation coefficient ofr=0.991 (Eformstands for formal potential whereasDNandANare the donor number and the acceptor number). The solvent effect on the position of the spectral absorption ofDPPHis also discussed;vmaxvalues show good linear regression with the π*-parameter introduced b