Electron Spin Resonance Absorption and Other Properties of Some Solid Hydrocarbon-Quinone Complexes

Crystalline solids have been prepared from aromatic hydrocarbons and tetrahalogenated benzoquinones. The solids contain one molecule of hydrocarbon for every molecule of quinone. The infrared and optical spectra of the solids, as well as their chemical properties, indicate that the components are bound by electronic donor-acceptor interactions which are weak compared to the intramolecular forces. Electron spin resonance absorption at 9500 Mc/sec was observed in nearly all the hydrocarbon-quinone solids prepared. However, perylene-quinone solids have been prepared which contain less than 1015 unpaired electron spins per gram. That is, they are practically diamagnetic. When unpaired electrons are present they are located at imperfections in the solid. Imperfections containing unpaired electron spins can be introduced thermally into the complexes. More than 1018 unpaired electrons per gram can be produced by heating perylene-ortho-quinone solids. The temperature dependences, g values, linewidths and spin-lattice relaxation times of the electron spin resonance absorption by the imperfection in some perylene-quinone solids have been investigated. The structure of the imperfection and the mechanism by which it is produced have been discussed.