2-Dicyanomethylene-1,3-Indanedione: A New Electron Acceptor

The electron affinity of 2-dicyanomethylene-1,3-indanedione (I) (1.33 ev), as computed from charge-transfer spectral analysis and from polarographic measurements of half-wave reduction potential, shows that the incorporation of the 2-dicyanomethylene moiety in 1,2,3-indanetrione (II) enhances its pi-acid character. The electron spin resonance spectrum of the anion radical of I, generated electrolytically in solution, shows hyperfine structure that is due to two nitrogen atoms and four equivalent hydrogen atoms.