Certain chemical compounds, which are aromatic heterocyclic-substituted derivatives of 4H-thiopyran-1,1,-dioxide given by the formula (I) wherein Het is a substituted or unsubstituted heterocyclic ring system containing at least one 5-membered heterocyclic aromatic ring; and R is an alkyl, aralkyl, or cycloalkyl group of 1 to about 10 carbon atoms, or an aryl group of 6 to about 12 carbon atoms, or a substituted or unsubstituted heterocyclic ring system containing at least one 5-membered aromatic heterocyclic ring, are electron-transport agents. These compounds exhibit good speed and toe voltage properties in electrophotographic elements. ##STR1##