A couple of naphthalenediimide 4 and 5 and series of perylenediimide derivatives 6–9 carrying TEMPO radical were prepared and their redox, FET, and magnetic properties were investigated. The radical compounds 4 and 6–9 were found to show antiferromagnetic interactions obeying the Curie–Weiss model, while the naphthalenediimide derivative 5 exhibited a singlet–triplet magnetic behavior and it could be well understood by the short oxygen-to-oxygen distance between the spin centers observed in its crystal structure. Owing presumably to their appropriate reduction potentials and structural motifs, exhibitions of n-type FET properties were disclosed in these radical compounds with mobilities of the order from 10−5 to 10−8 cm2 V−1 s−1 and apparent increase of mobilities was observed in the radical compounds 5 and 7 by the surface treatment with HMDS.