Charge-transfer properties of some paraquat salts

Abstract

A series of salts of the dication, NN′-dimethyl-4,4′-bipyridyl, with anions of the type MX₄ ^n–, where M can be a unibi-, or ter-valent cation and X is chloride, bromide, or iodide, has been prepared. Their formulae have been obtained chemically and in certain cases by complete structure analyses. The absorption spectra of the solids have been measured and an intermolecular charge-transfer band, from anion to cation, has been assigned. E.p.r. spectra of the FeCl₄ ^2– and of the Cu₂Cl₄ ^2– compound shows that these solids contain some of the reduced radical cation and some oxidised anion. The electrical conductivity of this type of compound is high. The relevance of the observations to the effect of the cation (paraquat) on electron-transfer in photosynthesis and oxidative phosphorylation is discussed.