The magnetic properties of a class of 1-D organic polymers with stable 2-azaphenalenyl radicals within the elementary units have been investigated theoretically. The nature and magnitude of the magnetic coupling between the electrons within the half-filled band (HFB) of the polymers were determined using the band theory. In all cases the pi-electrons within the HFB are ferromagnetically coupled with the main contribution of the Coulomb- and indirect exchange to the effective Heisenberg integral. (C) 2004 Elsevier B.V. All rights reserved.