DICYANOMETHYLENE DERIVATIVES OF SQUARIC ACID - ELECTROCHEMICAL-BEHAVIOR AND ESR INVESTIGATION

The electrochemical behaviour of mono- and bisdicyanomethylene-substit uted squaric acid dianion was investigated in dimethylformamide and ac etonitrile on a Pt electrode. In cyclic voltammetry the oxidation of t hese dianions involves two successive, chemically reversible, one-elec tron processes, affording the corresponding radical anions and neutral species. The redox potentials are strongly dependent upon the number of dicyanomethylene substituents. Whereas the neutral species are stab le only in the time scale of the voltammetric experiments, the radical anions can be accumulated by macroscale electrolysis. The ESR spectra of these radicals are reported. The monosubstituted dianion is proton ated by electrochemical oxidation of hydrogen, whereas the disubstitut ed ones are not. Compounds obtained from the disubstituted dianions an d the methyl viologen dication are also described.