Monomethyl and dimethyl tetrathionaphthalenes and tetraselenonaphthalenes have been developed as modified electron donors. Introduction of methyl groups is very helpful in enhancing the inherent low solubilities of the parent compounds. In the cyclic voltammograms, they show two reversible redox waves, whose first and second oxidation potentials are gradually lowered with the increasing number of the introduced methyl groups. They all are able to form charge-transfer complexes with tetracyanoquinodimethane. Irrespective of the chalcogen kind of the donor, the complexes of the dimethyl derivatives are conductive, while those of the monomethyl derivatives are insulating. The different conductivities are explained by the difference of their crystal structures, which are studied by infrared spectroscopy.