G. Farnia et al., DICYANOMETHYLENE DERIVATIVES OF SQUARIC ACID - ELECTROCHEMICAL-BEHAVIOR AND ESR INVESTIGATION, Journal of electroanalytical chemistry [1992], 404(2), 1996, pp. 261-269
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.