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A generation ago scientists at Du Pont's Central Research and Development Department sought to prepare, understand, and exploit organic molecules lacking aliphatic hydrogens and possessing a large cyano group to carbon ratio. Like many other ambitious quests the anticipated goal (of commercializing a new family of polymers) was not realized. Nonetheless, the discoveries made during this pursuit have made a permanent mark on the evolution of science. Most notably, the discovery of tetracyanoethylene (TCNE), and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ), and the remarkable stability of their radical anions led to an unusual series of charge transfer salts. Many of the TCNQ electron-transfer salts exhibit high, metal-like, dc electrical conductivity. These initial observations led to the evolutionary development of conducting polymers and the realization of molecular based ferromagnets.

Our continued study of derivatives of the 7,7,8,8-tetracyanoquinodimethan anion–radical (TCNQ−•) has shown that the simple N-methylphenazinium salt (IIa) exhibits a volume electrical resistivity of 7 × 10−3Ω cm and thus is the most highly electrically conductive organic compound known. In contrast, the N-ethyl analogue has a resistivity of 109Ω cm. Electrical properties of pyrazinium, quinoxalinium, and phenazinium analogues, including phenazine-derived cation–radical salts of TCNQ−•, are discussed. Qualitative observations are made concerning the electron paramagnetic resonance of the N,N′-dimethyldihydrophenazinylium cation–radical.