Structure and redox behaviour of the bis(carbodicyano)cyclobutendione dianion and radical anion

Abstract

The 1,2-carbodicyanocyclobut-1,2-en-3,4-dione is a redox system which is formed by a dianion, a radical anion, and a neutral species, all connected by reversible and monoelectronic reactions. The stability of these compounds decreases with increasing degree of oxidation. The structure of the radical anion and of the dianion is that of conjugated dicarbonyl compounds with the highest density of the unpaired electron in the radical and of the two net negative charges in the dianion localized on the dicyanomethylene carbon atoms. The remaining π electrons are distributed over all the sp² carbons, and the oxygen atoms.