N-methyl derivatives of pyridinium with TCNQ are 1:2 charge transfer salts of tetracyanoquinodimethane. Despite the fact that the TCNQ chains should be a priori quarter filled bands, these systems are insulators with a gap of approximately 0.6 eV. Disordering these systems by irradiation slows down the charge carriers and changes their density. It creates a large variety of new experimental situations where the current carrying, heat carrying and magnetic excitations can be examined and compared. Conductivity and thermopower data concerning 22 nominally pure and irradiated samples of 3 different compounds are presented and discussed together with a preliminary electron spin resonance experiment, and compared to the most current models in the field. In nominally pure samples and at low irradiation doses, a single-electron, extended state semiconducting picture explains surprisingly well the main features of the transport properties. But the success of this phenomenology is only superficial and cannot explain the whole set of results, even when localized states near the band edges are introduced for the purpose of describing the high-disorder limit. The mobilities deduced from the above model are very low (∼1 cm 2 /V.s), even in the non-irradiated samples, and suggest the possible presence of polaronic states. The low disorder to high disorder crossover observed in the transport properties could be viewed as a large polaron to small polaron transition. However, turning on the electron-phonon interaction is, by no means, enough for understanding the insulating character of these compounds. One also needs substantial electron-electron interactions. N-methyl derivatives of pyridinium with TCNQ are either Mott insulators, or spinless fermion half-filled band Peierls insulators. The main current carrying excitations are excitons in the former case and soliton-antisoliton pairs in the latter. Both excitations exhibit the electron-hole symmetry suggested by the experimental results. Possibly pure and irradiated N-methyl derivatives of pyridinium with TCNQ provide an experimental indication of the presence of solitons with charge ±e/2 predicted by Hubbard and Rice Etude de la nature des excitations magnetiques et des excitations porteuses de courant par mesure de la conductivite electrique et du pouvoir thermoelectrique d'echantillons purs et irradies de derives de la pyridine avec TCNQ. Presentation d'une experience de RPE et discussion des resultats