The Electronic Spectra of the Anion Radical Salts Derived from 2,3-Dicyano-1,4-benzoquinone and 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone

The anion radical salts derived from 2,3-dicyano-1,4-benzoquinone and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone were prepared. The absorption spectra in an acetonitrile solution and the solid-state spectra were examined for these anion radical salts. Unlike the absorption spectra in solution, in the solid-state spectra strong charge-transfer bands appeared and there were blue-shifts of the high-energy bands. These spectroscopic features were discussed on the basis of the charge-transfer interaction between the anion radicals. The solid-state properties of these salts were compared with those previously investigated for the anion radical salts of the halogen-substituted p-benzoquinones.