Novel radical ion salts of the formula ##STR1## wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 independently of one another are each hydrogen, methyl, ethyl, phenyl, methoxy, ethoxy, fluorine, chlorine or bromine, or R.sup.1 or R.sup.1 and R.sup.3 may furthermore be tert-butyl and/or R.sup.1 and R.sup.2 and/or R.sup.3 and R.sup.4 together may in each case form a radical of the formula ##STR2## where z is 0, 1, 2 or 3, and the fused aromatic rings are unsubstituted or monosubstituted or disubstituted by chlorine, bromine, methyl and/or methoxy, M.sup.m.sym. is an m-valent alkali metal, alkaline earth metal, transition metal, tin, lead, thallium, ammonium, phosphonium, arsonium or stibonium ion, k is from 1 to 5, l is from 0.1 to 4, m is from 1 to 3, n is from 0.1 to 4, x is from 0 to 2 and y is from 0 to 6, and k, l, n, x and y may furthermore be non-integral numbers and (l+x)=n.m, are electrically conductive in the crystalline state. A number of the salts are stable at 300.degree. C. and above.The salts (I) are useful as electrical semiconductors and photoconductors, as electrode or storage material, in electric batteries, etc.